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((cs1 config|name-list-style=vanc))((Repetition|date=January 2024|for=removal of information stated multiple times across the page))

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((Infobox medical condition (new)
| name            = Group B Streptococcal infection
| synonyms        = Group B streptococcal disease
| image           = Streptococcus agalactiae.tif
| caption         = ''Streptococcus agalactiae''- Gram stain
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'''Group B streptococcal infection''', also known as '''Group B streptococcal disease''' or just '''Group B strep''' infection, is the [[Infection|infectious]] [[disease]] caused by the [[bacterium]] ''[[Streptococcus agalactiae]]'' (''S. agalactiae''), which is also known as group B [[streptococcus]] or GBS. Infection with GBS can cause serious illness and sometimes death, especially in newborns, the elderly, and people with compromised [[immune systems]]. The most severe form of group B streptococcal disease is [[neonatal meningitis]] in infants, which is frequently lethal and can cause permanent [[Cognitive impairment|neuro-cognitive impairment]].

''S. agalactiae'' was recognized as a [[pathogen]] in cattle by [[Edmond Nocard]] and Mollereau in the late 1880s. It can cause bovine [[mastitis]] ([[inflammation]] of the [[udder]]) in dairy cows. The species name "agalactiae" meaning "no milk", alludes to this. Its significance as a human pathogen was first described in 1938,<ref name="Fry 1938">((cite journal| vauthors = Fry RM |title=Fatal infections by haemolytic streptococcus group B.|journal=The Lancet|date=1938|volume=231 | issue=5969|pages=199–201|doi=10.1016/S0140-6736(00)93202-1))</ref> and in the early 1960s, GBS came to be recognized as a major cause of infections in newborns.<ref name="Eickhoff 1964">((cite journal | vauthors = Eickhoff TC, Klein JO, Daly AK, Ingall D, Finland M | title = Neonatal Sepsis and Other Infections Due to Group B Beta-Hemolytic Streptococci | journal = The New England Journal of Medicine | volume = 271 | issue = 24 | pages = 1221–1228 | date = December 1964 | pmid = 14234266 | doi = 10.1056/NEJM196412102712401 ))</ref>

In most people, ''Streptococcus agalactiae'' is a harmless [[commensal]] [[bacterium]] being part of the normal human [[microbiota]] colonizing the gastrointestinal and genitourinary tracts. Up to 30% of healthy human adults are [[asymptomatic carriers]] of GBS.<ref name="Edwards 2010">((cite book |title=Streptococcus agalactiae (group B streptococcus). Mandell GL, Bennett JE, Dolin R (eds) Principles and practice of infectious diseases. Vol 2 |vauthors=Edwards MS, Baker CJ |date=2010 |publisher=Elsevier. |isbn=978-0-443-06839-3 |edition=7th. |pages=Chapter 202))</ref><ref name="Edwards 2011">((cite book |title=Group B streptococcal infections. Infectious Diseases of the Fetus and Newborn Infant |vauthors=Edwards MS, Nizet V |date=2011 |publisher=Elsevier |isbn=978-0-443-06839-3 |edition=7th. |pages=419–469))</ref>((TOC limit|3))

== Laboratory identification ==
[[File:Streptococcus agalactiae on blood agar.JPG|thumb|β-haemolytic colonies of ''Streptococcus agalactiae'', blood agar 18h at 36&nbsp;°C]]
[[Image:CAMP test.JPG|thumb|Positive CAMP test indicated by the formation of an arrowhead where ''S. agalactiae'' meets ''Staphylococcus aureus'' (white middle streak)]] [[File:S agalactiae vagino-rectal culture GRANADA.png|thumb|Red colonies of ''S. agalactiae'' in granada agar, vagino-rectal culture 18h incubation 36&nbsp;°C anaerobiosis]]
As mentioned, ''S. agalactiae'' is a Gram-positive coccus with a tendency to form chains, beta-haemolytic, catalase-negative, and facultative anaerobe ([[anaerobic organism]]). GBS grows readily on [[blood agar]] plates as microbial colonies surrounded by a narrow zone of β-[[haemolysis]].
GBS is characterized by the presence in the [[cell wall]] of the group B [[antigen]] of the [[Lancefield classification]] ([[Lancefield grouping]]) that can be detected directly in intact bacteria using [[latex agglutination]] tests.<ref name="Tille- Bailey&Scott's">((cite book| vauthors = Tille P |title=Bailey & Scott's Diagnostic Microbiology|date=2014|publisher=Elsevier.|isbn=978-0-323-08330-0|edition=13th.))</ref><ref name="Rosa 2017">((cite journal | vauthors = Rosa-Fraile M, Spellerberg B | title = Reliable Detection of Group B Streptococcus in the Clinical Laboratory | journal = Journal of Clinical Microbiology | volume = 55 | issue = 9 | pages = 2590–2598 | date = September 2017 |pmid = 28659318 | pmc = 5648696 | doi = 10.1128/JCM.00582-17 ))</ref>
<ref name="ASM 2020">((cite journal | vauthors = Filkins L, Hauser JR, Robinson-Dunn B, Tibbetts R, Boyanton BL, Revell P | title = American Society for Microbiology Provides 2020 Guidelines for Detection and Identification of Group B Streptococcus | journal = Journal of Clinical Microbiology | volume = 59 | issue = 1 | pages = | date = December 2020 | pmid = 33115849 | pmc = 7771461 | doi = 10.1128/JCM.01230-20 ))</ref><ref name="ASM.org">((Cite web |title=Guidelines for the Detection and Identification of Group B Streptococcus |url=https://asm.org:443/Guideline/Guidelines-for-the-Detection-and-Identification-of |access-date=2023-05-03 |website=ASM.org |language=en))</ref>

The [[CAMP test]] is also another important test for the identification of GBS. The CAMP factor acts synergistically with the staphylococcal β-haemolysin inducing enhanced haemolysis of sheep or bovine [[erythrocytes]].<ref name="Tille- Bailey&Scott's" />

GBS is also able to hydrolyse [[hippurate]], and this test can also be used to identify GBS.<ref name="Rosa 2017" />

Hemolytic GBS strains, when cultivated on [[granada medium]] after 24-48h at 35-37&nbsp;°C, produce ([[granadaene]]) and develop as orange-brick or red colonies that allows its straightforward and unequivocal identification.<ref name="Rosa-Fraile 1999">((cite journal | vauthors = Rosa-Fraile M, Rodriguez-Granger J, Cueto-Lopez M, Sampedro A, Gaye EB, Haro JM, Andreu A | title = Use of Granada medium to detect group B streptococcal colonization in pregnant women | journal = Journal of Clinical Microbiology | volume = 37 | issue = 8 | pages = 2674–2677 | date = August 1999 | pmid = 10405420 | doi = 10.1128/JCM.37.8.2674-2677.1999 | pmc = 85311 ))</ref>

Identification of GBS could also be carried out easily using  matrix-assisted laser desorption ionization-time of flight ([[MALDI-TOF]]) [[mass spectrometry]].<ref name="Binghuai 2014">((cite journal | vauthors = Binghuai L, Yanli S, Shuchen Z, Fengxia Z, Dong L, Yanchao C | title = Use of MALDI-TOF mass spectrometry for rapid identification of group B Streptococcus on chromID Strepto B agar | journal = International Journal of Infectious Diseases | volume = 27 | pages = 44–48 | date = October 2014 | pmid = 25220051 | url=https://www.ijidonline.com/action/showPdf?pii=S1201-9712%2814%2901586-0|doi = 10.1016/j.ijid.2014.06.023  | doi-access = free ))</ref><ref name="To- MALDI">((cite journal | vauthors = To KN, Cornwell E, Daniel R, Goonesekera S, Jauneikaite E, Chalker V, Le Doare K | title = Evaluation of matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) for the Identification of Group B Streptococcus | journal = BMC Research Notes | volume = 12 | issue = 1 | pages = 85 | date = February 2019  | pmid = 30764872 | pmc = 6376729 | doi = 10.1186/s13104-019-4119-1 | doi-access = free ))</ref> and [[Nucleic acid tests]] (NAATs).<ref name="Rosa 2017" />

Additionally GBS colonies can be tentatively identified after their appearance in chromogenic agar media.<ref name="Rosa 2017" /><ref name="Verani 2010">((cite journal| vauthors = Verani JR, McGee L, Schrag SJ |title=Prevention of perinatal group B streptococcal disease: revised guidelines from CDC |journal=MMWR Recomm. Rep. |date=2010|volume=59 |issue=(RR-10) |pages=1–32|url=https://www.cdc.gov/mmwr/pdf/rr/rr5910.pdf))</ref><ref name="El Aila">((cite journal | vauthors = El Aila NA, Tency I, Claeys G, Saerens B, Cools P, Verstraelen H, Temmerman M, Verhelst R, Vaneechoutte M | display-authors = 6 | title = Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women | journal = BMC Infectious Diseases | volume = 10 | pages = 285 | date = September 2010 | pmid = 20920213 | pmc = 2956727 | doi = 10.1186/1471-2334-10-285 | doi-access = free ))</ref>

Nevertheless, GBS-like colonies that develop in chromogenic media should be confirmed as GBS using additional reliable tests (e.g.latex agglutination or the CAMP test) to avoid potential mis-identification.<ref name="Rosa 2017" /><ref name="ASM.org" />

A summary of the laboratory techniques for GBS identification is depicted in Ref.<ref name="Rosa 2017" />

===Colonization versus infection===
GBS is found in the gastrointestinal and genitourinary tract of humans and is normal component of the intestinal and vaginal [[microbiota]] in some women.<ref name="Edwards 2010" /><ref name="ACOG 2020">((cite journal | vauthors =  | title = Prevention of Group B Streptococcal Early-Onset Disease in Newborns: ACOG Committee Opinion, Number 797 | journal = Obstetrics and Gynecology | volume = 135 | issue = 2 | pages = e51–e72 | date = February 2020 |url= https://journals.lww.com/greenjournal/fulltext/2020/02000/prevention_of_group_b_streptococcal_early_onset.43.aspx|pmid = 31977795 | doi = 10.1097/AOG.0000000000003668 | s2cid = 210891255 ))</ref>

In different studies, GBS vaginal colonization rate ranges from 4 to 36%, with most studies reporting rates over 20%,
with an estimation for maternal GBS colonization worldwide of 18% with large variations among countries (11%–35%).<ref name="Rusell Seale 2017">((cite journal | vauthors = Russell NJ, Seale AC, O'Driscoll M, O'Sullivan C, Bianchi-Jassir F, Gonzalez-Guarin J, Lawn JE, Baker CJ, Bartlett L, Cutland C, Gravett MG, Heath PT, Le Doare K, Madhi SA, Rubens CE, Schrag S, Sobanjo-Ter Meulen A, Vekemans J, Saha SK, Ip M | display-authors = 6 | title = Maternal Colonization With Group B Streptococcus and Serotype Distribution Worldwide: Systematic Review and Meta-analyses | journal = Clinical Infectious Diseases | volume = 65 | issue = suppl_2 | pages = S100–S111 | date = November 2017 | pmid = 29117327 | doi = 10.1093/cid/cix658 | pmc = 5848259 ))</ref>

Vaginal or rectal colonization may be intermittent, transitory, or persistent.<ref name="ACOG 2020" /> These variations in the reported prevalence of [[asymptomatic]] (presenting no symptoms of disease) colonization could be related to the different detection methods used, and differences in populations studied.<ref name="Verani 2010" /><ref name="Barcaite 2008">((cite journal | vauthors = Barcaite E, Bartusevicius A, Tameliene R, Kliucinskas M, Maleckiene L, Nadisauskiene R | title = Prevalence of maternal group B streptococcal colonisation in European countries | journal = Acta Obstetricia et Gynecologica Scandinavica | volume = 87 | issue = 3 | pages = 260–271 | date = 2008 | pmid = 18307064 | doi = 10.1080/00016340801908759 | s2cid = 25897076 | url=https://obgyn.onlinelibrary.wiley.com/doi/epdf/10.1080/00016340801908759))</ref><ref name="Rodriguez-Granger 2012">((cite journal | vauthors = Rodriguez-Granger J, Alvargonzalez JC, Berardi A, Berner R, Kunze M, Hufnagel M, Melin P, Decheva A, Orefici G, Poyart C, Telford J, Efstratiou A, Killian M, Krizova P, Baldassarri L, Spellerberg B, Puertas A, Rosa-Fraile M | display-authors = 6 | title = Prevention of group B streptococcal neonatal disease revisited. The DEVANI European project | journal = European Journal of Clinical Microbiology & Infectious Diseases | volume = 31 | issue = 9 | pages = 2097–2104 | date = September 2012 | pmid = 22314410 | doi = 10.1007/s10096-012-1559-0 | s2cid = 15588906 ))</ref>
Though GBS is an asymptomatic and harmless colonizer of the gastrointestinal human tract in up to 30% of otherwise healthy adults, including pregnant women,<ref name="Edwards 2011" /><ref name="Barcaite 2008" /> this opportunistic harmless bacterium can, in some circumstances, cause severe invasive infections.<ref name="Edwards 2010" />

== Pregnancy ==
Though GBS colonization is [[asymptomatic]] and, in general, does not cause problems, it can sometimes cause serious illness for the mother and the baby during gestation and after delivery. GBS infections in the mother can cause [[chorioamnionitis]] (intra-amniotic infection or severe infection of the placental tissues) infrequently, postpartum infections (after birth) and it had been related with prematurity and fetal death.<ref name="Muller-Morbidity">((cite journal | vauthors = Muller AE, Oostvogel PM, Steegers EA, Dörr PJ | title = Morbidity related to maternal group B streptococcal infections | journal = Acta Obstetricia et Gynecologica Scandinavica | volume = 85 | issue = 9 | pages = 1027–1037 | date = 2016 |pmid = 16929406 | doi = 10.1080/00016340600780508 | s2cid = 11745321 | doi-access = free ))</ref>

GBS [[urinary tract infections]], more than 100.000 CFU ([[colony forming units]]) /mL, may induce labour in pregnant women and cause premature delivery ([[preterm birth]]) and [[miscarriage]] and requires antibiotic treatment. The presence of GBS in the urine of a pregnant woman, in any colony count, should be considered a marker of heavy GBS colonization and an indication for intra partum antibiotic prophylaxis (IAP).<ref name="Edwards 2011" /><ref name="ACOG 2020" /><ref name="Willians 2014">((cite book | vauthors = Cunningham FG, Leveno K, Bloom S, Spong C, Dashe J, Hoffman B, Casey B, Sheffield J |title=Willians Obstetrics |date=2014 |publisher=McGraw Hill |isbn=978-0-07-179894-5 |edition=24th ))</ref>

=== Newborns ===

In the western world, GBS (in the absence of effective prevention measures) is the main cause of bacterial infections in newborns, such as [[sepsis]], [[pneumonia]], and [[meningitis]], which can lead to death or long-term [[sequelae|after effects]].<ref name="Edwards 2011" /><ref name="Libster 2012">((cite journal | vauthors = Libster R, Edwards KM, Levent F, Edwards MS, Rench MA, Castagnini LA, Cooper T, Sparks RC, Baker CJ, Shah PE | display-authors = 6 | title = Long-term outcomes of group B streptococcal meningitis | journal = Pediatrics | volume = 130 | issue = 1 | pages = e8-15 | date = July 2012 | pmid = 22689869 | doi = 10.1542/peds.2011-3453 | s2cid = 1013682 ))</ref><ref name="AAP Puopolo 2019">((cite journal | vauthors = Puopolo KM, Lynfield R, Cummings JJ | title = Management of Infants at Risk for Group B Streptococcal Disease | journal = Pediatrics | volume = 144 | issue = 2 | page = e20191881 | date = August 2019 | pmid = 31285392 | doi = 10.1542/peds.2019-1881 | s2cid = 195843897 | doi-access = free ))</ref><ref name=":0">((Cite journal |last1=Raabe |first1=Vanessa N. |last2=Shane |first2=Andi L. |date=March 2019 |title=Group B Streptococcus (Streptococcus agalactiae) |journal=Microbiology Spectrum |volume=7 |issue=2 |pages=10.1128/microbiolspec.GPP3–0007–2018 |doi=10.1128/microbiolspec.GPP3-0007-2018 |issn=2165-0497 |pmc=6432937 |pmid=30900541))</ref>

GBS infections in newborns are separated into two clinical types, early-onset disease (GBS-EOD) and late-onset disease (GBS-LOD). GBS-EOD manifests from 0 to 7 living days in the newborn, most of the cases of EOD being apparent within 24 h from birth. GBS-LOD starts between 7 and 90 days after birth.<ref name="Edwards 2011" /><ref name="Verani 2010" /><ref name="ACOG 2020" /><ref name="AAP Puopolo 2019" />

Roughly 50% of newborns of GBS colonized mothers are also GBS colonized and (without prevention measures) 1-2% of these newborns will develop GBS-EOD.<ref name="ACOG 2020" /><ref name="Boyer 1985">((cite book|vauthors=Boyer KM, Gotoff SP |title=Strategies for chemoprophylaxis of GBS early-onset infections|date=1985|volume=35|pages=267–280|doi=10.1159/000410380|pmid=3931544|series=Antibiotics and Chemotherapy|isbn=978-3-8055-3953-1|chapter=Strategies for Chemoprophylaxis of GBS Early-Onset Infections1))</ref>

The most common clinical [[syndromes]] of GBS-EOD are sepsis, pneumonia, and (less commonly) meningitis. Pneumonia and sepsis are frequently seen together or sequentially. Neonates with meningitis often present similarly to those with other syndromes, before progressing to symptoms of meningitis. Examination of the infant's [[cerebrospinal fluid]] is often necessary to rule out meningitis.<ref name="Edwards 2011" /><ref name="AAP Puopolo 2019" /><ref name="Polin 2012">((cite journal | vauthors = Polin RA | title = Management of neonates with suspected or proven early-onset bacterial sepsis | journal = Pediatrics | volume = 129 | issue = 5 | pages = 1006–1015 | date = May 2012 | pmid = 22547779 | doi = 10.1542/peds.2012-0541 | s2cid = 230591 | doi-access = free ))</ref><ref name="Martinez 2015">((cite journal | vauthors = Martinez E, Mintegi S, Vilar B, Martinez MJ, Lopez A, Catediano E, Gomez B | title = Prevalence and predictors of bacterial meningitis in young infants with fever without a source | journal = The Pediatric Infectious Disease Journal | volume = 34 | issue = 5 | pages = 494–498 | date = May 2015 | pmid = 25461476 | doi = 10.1097/inf.0000000000000629 | s2cid = 43717212 ))</ref>

A large minority of infants with ''S. agalactiae'' sepsis have a [[polymicrobial infection]], with one or more other species of bacteria also contributing to the septic disease. The most common of these organisms is ''[[Staphylococcus aureus]]''.<ref name=":0" />

Colonization with GBS during labor is the primary risk factor for the development of GBS-EOD. GBS-EOD is acquired vertically ([[vertical transmission]]), through exposure of the fetus or the baby to GBS from the vagina of a colonized woman, either ''in utero'' (because of ascending infection) or during birth, after rupture of membranes. Infants can also be infected during passage through the birth canal; however, newborns who acquire GBS through this route can only become colonized, and these colonized infants usually do not develop GBS-EOD.<ref name="ACOG 2020" /><ref name="Russell Seale Risk 2017">((cite journal | vauthors = Russell NJ, Seale AC, O'Sullivan C, Le Doare K, Heath PT, Lawn JE, et al   | title = Risk of Early-Onset Neonatal Group B Streptococcal Disease With Maternal Colonization Worldwide: Systematic Review and Meta-analyses | journal = Clinical Infectious Diseases | volume = 65 | issue = suppl_2 | pages = S152–S159 | date = November 2017 | pmc = 5850448 | doi = 10.1093/cid/cix655 | pmid = 29117325 ))</ref>

Though maternal GBS colonization is the key determinant for GBS-EOD, other factors also increase the risk. These factors are:<ref name="Edwards 2011" /><ref name="Verani 2010" /><ref name="ACOG 2020" />
* Onset of labor before 37 weeks of gestation ([[premature birth]])
* [[Prolonged rupture of membranes]] (longer duration of membrane rupture) (≥18 h before delivery)
* GBS [[bacteriuria]] during pregnancy
* Intrapartum (during childbirth) fever (>38&nbsp;°C, >100.4&nbsp;°F)
* Amniotic infections (chorioamnionitis)
* Young maternal age
* Maternal HIV-infection <ref name="Dauby 2016">((cite journal | vauthors = Dauby N, Chamekh M, Melin P, Slogrove AL, Goetghebuer T | title = Increased Risk of Group B ''Streptococcus'' Invasive Infection in HIV-Exposed but Uninfected Infants: A Review of the Evidence and Possible Mechanisms | journal = Frontiers in Immunology | volume = 7 | pages = 505 | date = 2016 | pmid = 27899925 | pmc = 5110531 | doi = 10.3389/fimmu.2016.00505 | doi-access = free ))</ref>

Nevertheless, most babies who develop GBS-EOD are born to colonized mothers without any of these risk factors.<ref name="Verani 2010" />

Heavy GBS vaginal colonization may be associated with a higher risk for GBS-EOD.  Women who had one of these risk factors but who are not GBS colonized during labor are at low risk for GBS-EOD compared to women who were colonized prenatally, but had none of the aforementioned risk factors.<ref name="Boyer 1985" />

Presence of low levels of anticapsular [[antibodies]] against GBS in the mother are also of great importance for the development of GBS-EOD.<ref name="Baker 1976">((cite journal | vauthors = Baker CJ, Kasper DL | title = Correlation of maternal antibody deficiency with susceptibility to neonatal group B streptococcal infection | journal = The New England Journal of Medicine | volume = 294 | issue = 14 | pages = 753–756 | date = April 1976 | pmid = 768760 | doi = 10.1056/nejm197604012941404 ))</ref><ref name="Baker 1981">((cite journal | vauthors = Baker CJ, Edwards MS, Kasper DL | title = Role of antibody to native type III polysaccharide of group B Streptococcus in infant infection | journal = Pediatrics | volume = 68 | issue = 4 | pages = 544–549 | date = October 1981 | pmid = 7033911 | doi = 10.1542/peds.68.4.544 | s2cid = 38905874 ))</ref>

Because of that, a previous sibling with GBS-EOD is also an important risk factor for the development of the infection in subsequent deliveries, probably reflecting the lack of protective antibodies in the mother.<ref name="Verani 2010" /><ref name="AAP Puopolo 2019" />

Overall, the case fatality rates from GBS-EOD have declined, from 50% observed in studies from the 1970s to between 2 and 10% in recent years, mainly as a consequence of improvements in therapy and management. Fatal neonatal infections by GBS are more frequent among premature infants.
<ref name="Edwards 2011" /><ref name="Verani 2010" /><ref name="Edmond 2012">((cite journal | vauthors = Edmond KM, Kortsalioudaki C, Scott S, Schrag SJ, Zaidi AK, Cousens S, Heath PT | title = Group B streptococcal disease in infants aged younger than 3 months: systematic review and meta-analysis | journal = Lancet | volume = 379 | issue = 9815 | pages = 547–556 | date = February 2012 | pmid = 22226047 | doi = 10.1016/s0140-6736(11)61651-6 | s2cid = 15438484 | url = https://researchonline.lshtm.ac.uk/id/eprint/20551/1/1-s2.0-S0140673611616516-main.pdf__tid%3D9d429e3a-c455-11e5-a600-00000aab0f02%26acdnat%3D1453830949_98cb60cd0e0e2eb19caa5b2408b0e44d ))</ref>

Today, the mortality associated with GBS EOD in the US is 2.1% among term newborns and 19.2% among preterm newborns.<ref name="AAP Puopolo 2019" /><ref name = "Nanduri_2019">((cite journal | vauthors = Nanduri SA, Petit S, Smelser C, Apostol M, Alden NB, Harrison LH, Lynfield R, Vagnone PS, Burzlaff K, Spina NL, Dufort EM, Schaffner W, Thomas AR, Farley MM, Jain JH, Pondo T, McGee L, Beall BW, Schrag SJ | display-authors = 6 | title = Epidemiology of Invasive Early-Onset and Late-Onset Group B Streptococcal Disease in the United States, 2006 to 2015: Multistate Laboratory and Population-Based Surveillance | journal = JAMA Pediatrics | volume = 173 | issue = 3 | pages = 224–233 | date = March 2019 | pmid = 30640366 | pmc = 6439883 | doi = 10.1001/jamapediatrics.2018.4826 ))</ref>

GBS-LOD affects infants from 7 days to 3 months of age and has a lower [[case fatality rate]] (1%-6%) than GBS-EOD. Clinical syndromes of GBS-LOD are bacteremia without a focus (65%), meningitis (25%), [[cellulitis]], [[osteoarthritis]], and pneumonia.
Prematurity has been reported to be the main risk factor. Each week of decreasing gestation increases the risk by a factor of 1.34 for developing GBS-LOD.<ref>((cite journal | vauthors = Lin FY, Weisman LE, Troendle J, Adams K | title = Prematurity is the major risk factor for late-onset group B streptococcus disease | journal = The Journal of Infectious Diseases | volume = 188 | issue = 2 | pages = 267–271 | date = July 2003 | pmid = 12854082 | doi = 10.1086/376457 | doi-access = free ))</ref>

A heightened risk of GBS-LOD is related with  prematurity, low birth weight, maternal colonization and multiple-gestation pregnancies.<ref name="Karampatsas 2022">((cite journal |last1=Karampatsas K, Davies H, Mynarek M, Andrews N, Heath PT, Le Doare K. |title=Clinical Risk Factors Associated With Late-Onset Invasive Group B Streptococcal Disease: Systematic Review and Meta-Analyses |journal=Clin Infect Dis. |date=2022 |volume=75 |issue=7 |pages=1255–1264 |doi=10.1093/cid/ciac206 |pmid=35275986 |pmc=9525091 ))</ref>

GBS-LOD can not only be acquired through vertical transmission during delivery; it can also be acquired later from the mother from breast milk or from environmental, nosocomial and community sources.<ref>((cite journal |last1=Miselli F, Frabboni I, Di Martino M, Zinani I, Buttera M, Insalaco A, Stefanelli F, Lugli L, Berardi A. |title=Transmission of Group B Streptococcus in late-onset neonatal disease: a narrative review of current evidence |journal=Ther Adv Infect Dis . |date=2022 |volume=9 |page=20499361221142732 |doi=10.1177/20499361221142732 |pmid=36569815 |pmc=9780763 ))</ref>

GBS-LOD commonly shows nonspecific signs, and diagnosis should be made obtaining [[blood cultures]] in febrile newborns. ''S.agalactiae'' neonatal meningitis does not present with the hallmark sign of adult meningitis, a stiff neck. Instead, it presents with nonspecific symptoms, such as fever, vomiting and irritability, and can consequently lead to a late diagnosis. Hearing loss and mental impairment can be a long-term consequence of GBS meningitis.<ref name="Edwards 2011" /><ref name="Libster 2012"/>

==== Epidemiology ====
In 2021, it was estimated that 226 infants (49 per 100,000) in the United States had a clinically significant GBS infection, and that approximately 11 (2.4%) of those cases resulted in death.<ref name="Bacterial Core Surveillance 2021">((cite web |last1=Centers for Disease Control and Prevention |title=Active Bacterial Core Surveillance Report, Emerging Infections Program Network, Group B Streptococcus, 2021. |url=https://www.cdc.gov/abcs/downloads/GBS_Surveillance_Report_2021.pdf |website=Centers for Disease Control and Prevention. 2021 |access-date=17 November 2023))</ref>

=== Prevention of neonatal infection ===
Currently, the only reliable way to prevent GBS-EOD is administration of intrapartum [[intravenous]] (IV) antibiotics before delivery. That is to say, intrapartum [[antibiotic prophylaxis]] (IAP). IAP interrupts vertical transmission of GBS from the mother to the newborn and decreases the incidence of GBS-EOD.<ref name="Boyer Gadzala 1983">((cite journal | vauthors = Boyer KM, Gadzala CA, Kelly PD, Gotoff SP | title = Selective intrapartum chemoprophylaxis of neonatal group B streptococcal early-onset disease. III. Interruption of mother-to-infant transmission | journal = The Journal of Infectious Diseases | volume = 148 | issue = 5 | pages = 810–816 | date = November 1983 | pmid = 6355318 | doi = 10.1093/infdis/148.5.810 ))</ref>

Administration of [[intravenous]] (IV) antibiotics during labour. Intravenous [[penicillin]] or [[ampicillin]] given to GBS colonized women at the onset of labour and then again every four hours until delivery have been proven to be very effective at preventing vertical transmission of GBS from mother to baby and GBS-EOD. Penicillin G, 5 million units IV initial dose, then 3 million units every 4 hours until delivery or ampicillin, 2 g IV initial dose, then 1 g IV every 4 hours until delivery.<ref name="Edwards 2011" /><ref name="Verani 2010" /><ref name="ACOG 2020" />

Appropriate IAP in GBS colonized women should start as soon as possible once labour starts or waters have broken. When the first dose is given at least 4 hours before delivery, the risk of neonatal infection is very small; moreover, when given between 2–4 hours before delivery the risk is only partially reduced.<ref>((cite journal | vauthors = Lin FY, Brenner RA, Johnson YR, Azimi PH, Philips JB, Regan JA, Clark P, Weisman LE, Rhoads GG, Kong F, Clemens JD | display-authors = 6 | title = The effectiveness of risk-based intrapartum chemoprophylaxis for the prevention of early-onset neonatal group B streptococcal disease | journal = American Journal of Obstetrics and Gynecology | volume = 184 | issue = 6 | pages = 1204–1210 | date = May 2001 | pmid = 11349189 | doi = 10.1067/mob.2001.113875 ))</ref><ref name="De Cueto 1998">((cite journal | vauthors = de Cueto M, Sanchez MJ, Sampedro A, Miranda JA, Herruzo AJ, Rosa-Fraile M | title = Timing of intrapartum ampicillin and prevention of vertical transmission of group B streptococcus | journal = Obstetrics and Gynecology | volume = 91 | issue = 1 | pages = 112–114 | date = January 1998 | pmid = 9464732 | doi = 10.1016/s0029-7844(97)00587-5 | s2cid = 43765652 ))</ref><ref name="Berardi 2011">((cite journal | vauthors = Berardi A, Rossi C, Biasini A, Minniti S, Venturelli C, Ferrari F, Facchinetti F | title = Efficacy of intrapartum chemoprophylaxis less than 4 hours duration | journal = The Journal of Maternal-Fetal & Neonatal Medicine | volume = 24 | issue = 4 | pages = 619–625 | date = April 2011 | pmid = 20828241 | doi = 10.3109/14767058.2010.511347 | s2cid = 6697604 ))</ref>

Penicillin-[[allergic]] women without a history of [[anaphylaxis]] ([[angioedema]], [[respiratory distress]], or [[urticaria]]) following administration of a penicillin or a [[cephalosporin]] (low risk of anaphylaxis) could receive [[cefazolin]] (2 g IV initial dose, then 1 g IV every 8 hours until delivery) instead of penicillin or ampicillin.<ref name="Verani 2010" /><ref name="ACOG 2020" />

If the woman has a severe allergy to beta-lactams and the GBS isolated is susceptible to clindamycin then clindamycin is the recommended alternative.<ref name="ACOG 2020" />

For women with a high-risk penicillin allergy and whose GBS isolate is not susceptible to clindamycin intravenous vancomycin (20&nbsp;mg/kg intravenously every 8 hours, with a maximum of 2 gm per single dose) is the only valid option.<ref name="ACOG 2020" /><ref name="onlinelibrary.wiley.com">((cite journal | vauthors =  | title = Prevention of Early-onset Neonatal Group B Streptococcal Disease: Green-top Guideline No. 36 | journal = BJOG | volume = 124 | issue = 12 | pages = e280–e305 | date = November 2017 | pmid = 28901693 | doi = 10.1111/1471-0528.14821 | s2cid = 32700635 | doi-access = free ))</ref>
In women at high risk of anaphylaxis to penicillin the use of 
[[Erythromycin]] is not recommended today because the high proportion of GBS resistance to erythromycin (up to 44.8%).<ref name="Verani 2010" /><ref name="ACOG 2020" /> Testing for penicillin allergy and can be helpful for all GBS carrying pregnant women and will cancel the frequent use of other antibiotics for GBS-EOD IAP.<ref name="ACOG 2020" /> [[Antibiotic susceptibility testing]] <!-- (AST) --> of GBS isolates is crucial for appropriate antibiotic selection for IAP in penicillin-allergic women, because resistance to clindamycin, the most common agent used (in penicillin-allergic women), is increasing among GBS isolates. Appropriate methodologies (including inducible clindamycin resistance) for testing are important, because resistance to clyndamicin ([[antimicrobial resistance]]) can occur in some GBS strains that appear susceptible ([[antibiotic sensitivity]]) in certain susceptibility tests.<ref name="ASM.org" /><ref name="Verani 2010" />
For women who are at risk of penicillin allergy, the laboratory requisitions should indicate clearly this circumstance to ensure that the laboratory is aware for the need of testing GBS isolates for clindamycin susceptibility.
True penicillin allergy is rare with an estimated frequency of anaphylaxis of one to five episodes per 10,000 cases of penicillin therapy.<ref name="Desai Peni Allerg 2017">((cite journal | vauthors = Desai SH, Kaplan MS, Chen Q, Macy EM | title = Morbidity in Pregnant Women Associated with Unverified Penicillin Allergies, Antibiotic Use, and Group B Streptococcus Infections | journal = The Permanente Journal | volume = 21 | pages = 16–080 | date = 2017 | pmid = 28333608 | doi = 10.7812/TPP/16-080 | pmc = 5363897 ))</ref><ref name="Bhattacharya 2010">((cite journal | vauthors = Bhattacharya S | title = The facts about penicillin allergy: a review | journal = Journal of Advanced Pharmaceutical Technology & Research | volume = 1 | issue = 1 | pages = 11–17 | date = January 2010 | pmid = 22247826 | pmc = 3255391 ))</ref>
Penicillin administered to a woman with no history of [[β-lactam]] allergy has a risk of anaphylaxis of 0.04 to 4 per 100,000. Maternal anaphylaxis associated with GBS IAP occurs, but any morbidity associated with anaphylaxis is offset greatly by reductions in the incidence of GBS-EOD.<ref name="Verani 2010" />

IAPs have been considered to be associated with the emergence of resistant bacterial strains and with an increase in the incidence of early-onset infections caused by other pathogens, mainly [[Gram-negative]] bacteria such as ''[[Escherichia coli]]''. Nevertheless, most studies have not found an increased rate of non-GBS early-onset sepsis related to the widespread use of IAP.<ref name="Verani 2010" /><ref name="Baltimore 2001">((cite journal | vauthors = Baltimore RS, Huie SM, Meek JI, Schuchat A, O'Brien KL | title = Early-onset neonatal sepsis in the era of group B streptococcal prevention | journal = Pediatrics | volume = 108 | issue = 5 | pages = 1094–1098 | date = November 2001 | pmid = 11694686 | doi = 10.1542/peds.108.5.1094 ))</ref><ref name="Sutkin 2005">((cite journal | vauthors = Sutkin G, Krohn MA, Heine RP, Sweet RL | title = Antibiotic prophylaxis and non-group B streptococcal neonatal sepsis | journal = Obstetrics and Gynecology | volume = 105 | issue = 3 | pages = 581–586 | date = March 2005 | pmid = 15738028 | doi = 10.1097/01.aog.0000153492.30757.2f | s2cid = 22019440 ))</ref><ref name="Schrag&Hadler 2006">((cite journal | vauthors = Schrag SJ, Hadler JL, Arnold KE, Martell-Cleary P, Reingold A, Schuchat A | title = Risk factors for invasive, early-onset Escherichia coli infections in the era of widespread intrapartum antibiotic use | journal = Pediatrics | volume = 118 | issue = 2 | pages = 570–576 | date = August 2006 | pmid = 16882809 | doi = 10.1542/peds.2005-3083 | s2cid = 34908773 ))</ref>

Neither oral nor intramuscular antibiotics are effective in reducing the risk GBS-EOD.<ref name="ACOG 2020" />

Other strategies to prevent GBS-EOD have been studied, and [[chlorhexidine]] intrapartum vaginal cleansing has been proposed to help preventing GBS-EOD, nevertheless no evidence has been shown for the effectiveness of this approach.<ref name="Verani 2010" /><ref name="ACOG 2020" /><ref>((cite journal | vauthors = Cutland CL, Madhi SA, Zell ER, Kuwanda L, Laque M, Groome M, Gorwitz R, Thigpen MC, Patel R, Velaphi SC, Adrian P, Klugman K, Schuchat A, Schrag SJ | display-authors = 6 | title = Chlorhexidine maternal-vaginal and neonate body wipes in sepsis and vertical transmission of pathogenic bacteria in South Africa: a randomised, controlled trial | journal = Lancet | volume = 374 | issue = 9705 | pages = 1909–1916 | date = December 2009 | pmid = 19846212 | doi = 10.1016/S0140-6736(09)61339-8 | s2cid = 23418670 ))</ref><ref>((cite journal | vauthors = Ohlsson A, Shah VS, Stade BC | title = Vaginal chlorhexidine during labour to prevent early-onset neonatal group B streptococcal infection | journal = The Cochrane Database of Systematic Reviews | volume = 12 | issue = 12 | pages = CD003520 | date = December 2014 | url=https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD003520.pub3/epdf/full|pmid = 25504106 | doi = 10.1002/14651858.CD003520.pub3 ))</ref>

=== Identifying candidates to receive IAP ===
Two ways are used to select female candidates to IAP: the culture-based screening approach and the risk-based approach.<ref name="CDC 1996">((cite journal|last1=CDC|title=Prevention of Perinatal Group B Streptococcal Disease: A Public Health Perspective|journal=MMWR|date=1996|volume=45-RR7|pages=1–24|url=https://www.cdc.gov/mmwr/preview/mmwrhtml/00043277.htm))</ref>

The culture-based screening approach identifies candidates using lower vaginal and rectal cultures obtained between 35 and 37 weeks of gestation (or 36-37),<ref name="ACOG 2020" /> and IAP is administered to all GBS colonized women. The risk-based strategy identifies candidates to receive IAP by the aforementioned risk factors known to increase the probability of GBS-EOD without considering if the mother is or is not a GBS carrier.<ref name="Edwards 2011" /><ref name="Verani 2010" /><ref name="Clifford 2011">((cite journal | vauthors = Clifford V, Garland SM, Grimwood K | title = Prevention of neonatal group B streptococcus disease in the 21st century | journal = Journal of Paediatrics and Child Health | volume = 48 | issue = 9 | pages = 808–815 | date = September 2012 | pmid = 22151082 | doi = 10.1111/j.1440-1754.2011.02203.x | s2cid = 36906520 ))</ref>

IAP is also recommended for women with intrapartum risk factors if their GBS carrier status is not known at the time of delivery, and for women with GBS bacteriuria (in any colony count) during their pregnancy, and for women who have had an infant with GBS-EOD previously.
The risk-based approach is, in general, less effective than the culture-based approach,<ref name="Schrag 2002">((cite journal | vauthors = Schrag SJ, Zell ER, Lynfield R, Roome A, Arnold KE, Craig AS, Harrison LH, Reingold A, Stefonek K, Smith G, Gamble M, Schuchat A | display-authors = 6 | title = A population-based comparison of strategies to prevent early-onset group B streptococcal disease in neonates | journal = The New England Journal of Medicine | volume = 347 | issue = 4 | pages = 233–239 | date = July 2002 | pmid = 12140298 | doi = 10.1056/nejmoa020205 | doi-access = free ))</ref> because in most cases, GBS-EOD develops among newborns who have been born to mothers without risk factors.<ref name="Verani 2010" /><ref name="Boyer 1985" /><ref name="Gimenez 2015">((cite journal | vauthors = Giménez M, Sanfeliu I, Sierra M, et al.| title = [Group B streptococcal early-onset neonatal sepsis in the area of Barcelona (2004-2010). Analysis of missed opportunities for prevention] | journal = Enfermedades Infecciosas y Microbiologia Clinica | volume = 33 | issue = 7 | pages = 446–450 | date = 2015 | pmid = 25541009 | doi = 10.1016/j.eimc.2014.10.015  | s2cid = 196362631 ))</ref>

IAP is not required for women undergoing planned caesarean section in the absence of labour and with intact membranes, irrespective of the known GBS carriage status. ACOG recommendations state,<ref name="ACOG 2020" /> "Women with a positive prenatal GBS culture result who undergo a cesarean birth before the onset of labor and with intact membranes do not require GBS antibiotic prophylaxis".This recommendation is based on the fact that infants delivered via pre-labor cesarean section have less exposure to GBS in the vagina and have lower rates of GBS infection. Hence, despite the recommended universal recto-vaginal screening of all pregnant women at 36 0/7 to 37 6/7 weeks, women who undergo pre-labor cesarean sections do not need IAP, regardless of the screening test results.<ref name="Verani 2010" /><ref name="ACOG 2020" /><ref>((cite journal | vauthors = Håkansson S, Axemo P, Bremme K, et al. | title = Group B streptococcal carriage in Sweden: a national study on risk factors for mother and infant colonisation | journal = Acta Obstetricia et Gynecologica Scandinavica | volume = 87 | issue = 1 | pages = 50–58 | date = January 2008 | pmid = 18158627 |doi = 10.1080/00016340701802888 | s2cid = 38090766 | doi-access = free ))</ref>

Routine screening of pregnant women is performed in most developed countries such as the United States, France, Spain, Belgium and Canada, and data have shown falling incidences of GBS-EOD following the introduction of screening-based measures to prevent GBS-EOD.
<ref name="Rodriguez-Granger 2012" /><ref name="Phares 2008">((cite journal | vauthors = Phares CR, Lynfield R, Farley MM, Mohle-Boetani J, Harrison LH, Petit S, Craig AS, Schaffner W, Zansky SM, Gershman K, Stefonek KR, Albanese BA, Zell ER, Schuchat A, Schrag SJ | display-authors = 6 | title = Epidemiology of invasive group B streptococcal disease in the United States, 1999-2005 | journal = JAMA | volume = 299 | issue = 17 | pages = 2056–2065 | date = May 2008 | pmid = 18460666 | doi = 10.1001/jama.299.17.2056 | doi-access = free ))</ref><ref name="Le Doare- O'Driscoll 2017 et al">((cite journal |last1=Le Doare K, O'Driscoll M, Turner K, Seedat F|title=Intrapartum Antibiotic Chemoprophylaxis Policies for the Prevention of Group B Streptococcal Disease Worldwide: Systematic Review |journal=Clin Infect Dis. |date=2017 |volume=65 |issue=Suppl 2 |pages=s143-151 |doi=10.1093/cid/cix654 |pmid=29117324 |pmc=5850619 ))</ref>

The risk-based strategy is advocated, among other countries, in the United Kingdom and the Netherland.<ref name="Rodriguez-Granger 2012" />

The issue of cost-effectiveness of both strategies for identifying candidates for IAP is less clear-cut, and some studies have indicated that testing low risk women, plus IAP administered to high-risk women, and to those found to carry GBS is more cost-effective than the current UK practice.<ref name="Colbourn2007">((cite journal | vauthors = Colbourn T, Asseburg C, Bojke L, Philips Z, Claxton K, Ades AE, Gilbert RE | title = Prenatal screening and treatment strategies to prevent group B streptococcal and other bacterial infections in early infancy: cost-effectiveness and expected value of information analyses | journal = Health Technology Assessment | volume = 11 | issue = 29 | pages = 1–226, iii | date = August 2007 | pmid = 17651659 | doi = 10.3310/hta11290 | doi-access = free ))</ref> 
Other evaluations have also found the culture-based approach to be more cost-effective than the risk-based approach for the prevention of GBS-EOD.<ref name=pmid17848402>((cite journal | vauthors = Colbourn TE, Asseburg C, Bojke L, Philips Z, Welton NJ, Claxton K, Ades AE, Gilbert RE | display-authors = 6 | title = Preventive strategies for group B streptococcal and other bacterial infections in early infancy: cost effectiveness and value of information analyses | journal = BMJ | volume = 335 | issue = 7621 | pages = 655 | date = September 2007 |url= https://www.bmj.com/content/bmj/335/7621/655.full.pdf| doi = 10.1136/bmj.39325.681806.AD | pmid = 17848402 | pmc = 1995477 ))</ref><ref name="Kaambwa 2010">((cite journal | vauthors = Kaambwa B, Bryan S, Gray J, Milner P, Daniels J, Khan KS, Roberts TE | title = Cost-effectiveness of rapid tests and other existing strategies for screening and management of early-onset group B streptococcus during labour | journal = BJOG | volume = 117 | issue = 13 | pages = 1616–1627 | date = December 2010 | pmid = 21078057 | doi = 10.1111/j.1471-0528.2010.02752.x | s2cid = 25561127 | doi-access = free ))</ref>

Testing pregnant women to detect GBS carriers and giving IAP to those carrying GBS and to high-risk women has also been proposed and this approach is significantly more cost-effective than the use of the risk-factor approach.  One research paper calculated an expected net benefit to the UK government of such an approach of around £37 million a year, compared with the current [[RCOG]] approach.<ref name="Colbourn2007"/><ref name=pmid17848402/>

It has been reported that IAP does to not prevent all cases of GBS-EOD; its efficacy is estimated at 80%. The risk-based prevention strategy does not prevent about 33% of cases with no risk factors.<ref name="Vergnano 2010">((cite journal | vauthors = Vergnano S, Embleton N, Collinson A, Menson E, Russell AB, Heath P | title = Missed opportunities for preventing group B streptococcus infection | journal = Archives of Disease in Childhood. Fetal and Neonatal Edition | volume = 95 | issue = 1 | pages = F72–F73 | date = January 2010 | pmid = 19439431 | doi = 10.1136/adc.2009.160333 | s2cid = 38297857 ))</ref>

Up to 90% of cases of GBS-EOD would be preventable if IAP were offered to all GBS carriers identified by universal screening late in pregnancy, plus to the mothers in higher risk situations.<ref>((cite journal | vauthors = Steer PJ, Plumb J | title = Myth: Group B streptococcal infection in pregnancy: comprehended and conquered | journal = Seminars in Fetal & Neonatal Medicine | volume = 16 | issue = 5 | pages = 254–258 | date = October 2011 | pmid = 21493170 | doi = 10.1016/j.siny.2011.03.005 ))</ref>

Where insufficient intravenous antibiotics are given before delivery, the baby may be given antibiotics immediately after birth, although evidence is inconclusive as to whether this practice is effective or not.<ref name="Verani 2010" /><ref name="Siegel 1996">((cite journal | vauthors = Siegel JD, Cushion NB | title = Prevention of early-onset group B streptococcal disease: another look at single-dose penicillin at birth | journal = Obstetrics and Gynecology | volume = 87 | issue = 5 Pt 1 | pages = 692–698 | date = May 1996 | pmid = 8677068 | doi = 10.1016/0029-7844(96)00004-x   | s2cid = 40716699 ))</ref><ref name="Velaphi 2003">((cite journal | vauthors = Velaphi S, Siegel JD, Wendel GD, Cushion N, Eid WM, Sánchez PJ | title = Early-onset group B streptococcal infection after a combined maternal and neonatal group B streptococcal chemoprophylaxis strategy | journal = Pediatrics | volume = 111 | issue = 3 | pages = 541–547 | date = March 2003 | pmid = 12612234 | doi = 10.1542/peds.111.3.541 ))</ref><ref name="Woodgate 2004">((cite journal | vauthors = Woodgate P, Flenady V, Steer P | title = Intramuscular penicillin for the prevention of early onset group B streptococcal infection in newborn infants | journal = The Cochrane Database of Systematic Reviews | volume = 2004 | issue = 3 | pages = CD003667 | date = 2004 |  doi = 10.1002/14651858.CD003667.pub2 | pmid = 15266494 | pmc = 9029842 ))</ref>

[[File:Incidence of EOD & LOD GBS disease-CDC.tif|thumb|Falling incidence of EOD and LOD GBS disease in US-CDC]]

=== Home births and water birth ===
Home births are becoming increasingly popular in the UK. Recommendations for preventing GBS infections in newborns are the same for home births as for hospital births. Around 25% of women having home births probably carry GBS in their vaginas at delivery without knowing, and it could be difficult to follow correctly the recommendations of IAP and to deal with the risk of a severe allergic reaction to the antibiotics outside of a hospital setting.<ref name="GBS home birth">((cite web|last1=GROUP B STREP SUPPORT|title=FAQs35. Carrying GBS and home birth?|url=https://gbss.org.uk/frequently-asked-questions/|access-date=4 March 2021))</ref>
The RCOG and the ACOG guidelines suggest that birth in a pool is not contraindicated for GBS carriers who have been offered the appropriate IAP if no other contraindications to water immersion are present<ref name="ACOG 2020" /><ref name="RCOG 2017 Guidelines">((cite journal | vauthors =  | title = Prevention of Early-onset Neonatal Group B Streptococcal Disease: Green-top Guideline No. 36 | journal = BJOG | volume = 124 | issue = 12 | pages = e280–e305 | date = November 2017 |doi = 10.1111/1471-0528.14821| pmid = 28901693 | s2cid = 32700635 | doi-access = free ))</ref>

=== Screening for colonization ===
Approximately 10–30%  of women are colonized with GBS during pregnancy. Nevertheless, during pregnancy, colonization can be temporary, intermittent, or continual.<ref name="Verani 2010" /> Because the GBS colonization status of women can change during pregnancy, only cultures carried out ≤5 weeks before delivery predict quite accurately the GBS carrier status at delivery.<ref name="Yancey 1996">((cite journal | vauthors = Yancey MK, Schuchat A, Brown LK, Ventura VL, Markenson GR | title = The accuracy of late antenatal screening cultures in predicting genital group B streptococcal colonization at delivery | journal = Obstetrics and Gynecology | volume = 88 | issue = 5 | pages = 811–815 | date = November 1996 | pmid = 8885919 | doi = 10.1016/0029-7844(96)00320-1 ))</ref>

In contrast, if the prenatal culture is carried out more than 5 weeks before delivery, it is unreliable for accurately predicting the GBS carrier status at delivery. Because of that, testing for GBS colonization in pregnant women is recommended by the CDC at 36–37 weeks of gestation.<ref name="Verani 2010" /><ref name="Valkenburg 2010">((cite journal | vauthors = Valkenburg-van den Berg AW, Houtman-Roelofsen RL, Oostvogel PM, Dekker FW, Dörr PJ, Sprij AJ | title = Timing of group B streptococcus screening in pregnancy: a systematic review | journal = Gynecologic and Obstetric Investigation | volume = 69 | issue = 3 | pages = 174–183 | date = 2010 | pmid = 20016190 | doi = 10.1159/000265942  | s2cid = 26709882 ))</ref>

It is important to note that the [[American College of Obstetricians and Gynecologists|ACOG]] now recommends performing universal GBS screening between 36 and 37 weeks of gestation. This new recommendation provides a 5-week window for valid culture results that includes births that occur up to a gestational age of at least 41 weeks.<ref name="ACOG 2020" />

The clinical samples recommended for culture of GBS are swabs collected from the lower [[vagina]] and [[rectum]] through the [[external anal sphincter]].Vaginal-rectal samples should be collected using a flocked swab preferably. Compared with fiber swab, these swabs releases samples and microorganisms more efficiently than conventional fiber swabs.<ref name="ASM 2020" />
The sample should be collected swabbing the lower vagina (vaginal introitus) followed by the rectum (i.e., inserting the swab through the anal sphincter) using the same swab or two different swabs. Cervical, perianal, perirectal, or perineal specimens are not acceptable, and a [[speculum (medical)|speculum]] should not be used for sample collection.<ref name="Verani 2010" />
Samples (swabs) can be taken by healthcare professionals, or self-colected by the mother accurately after appropriate instruction.<ref name="Price 2006">((cite journal | vauthors = Price D, Shaw E, Howard M, Zazulak J, Waters H, Kaczorowski J | title = Self-sampling for group B streptococcus in women 35 to 37 weeks pregnant is accurate and acceptable: a randomized cross-over trial | journal = Journal of Obstetrics and Gynaecology Canada | volume = 28 | issue = 12 | pages = 1083–1088 | date = December 2006 | pmid = 17169231 | doi = 10.1016/s1701-2163(16)32337-4 ))</ref><ref name="Hicks 2009">((cite journal | vauthors = Hicks P, Diaz-Perez MJ | title = Patient self-collection of group B streptococcal specimens during pregnancy | journal = Journal of the American Board of Family Medicine | volume = 22 | issue = 2 | pages = 136–140 | date = 2009 |url=https://www.jabfm.org/content/jabfp/22/2/136.full.pdf | doi = 10.3122/jabfm.2009.02.080011| pmid = 19264936 | s2cid = 2208746 ))</ref><ref name="Arya 2008">((cite journal | vauthors = Arya A, Cryan B, O'Sullivan K, Greene RA, Higgins JR | title = Self-collected versus health professional-collected genital swabs to identify the prevalence of group B streptococcus: a comparison of patient preference and efficacy | journal = European Journal of Obstetrics, Gynecology, and Reproductive Biology | volume = 139 | issue = 1 | pages = 43–45 | date = July 2008 | pmid = 18255214 | doi = 10.1016/j.ejogrb.2007.12.005 ))</ref><ref name="Odubamowo 2023">((cite journal |last1=Odubamowo K, Garcia M, Muriithi F, Ogollah R, Daniels JP, Walker KF |title=Self-collected versus health-care professional taken swab for identification of vaginal-rectal colonisation with group B streptococcus in late pregnancy: a systematic review. |journal=Eur J Obstet Gynecol Reprod Biol |date=2023 |volume=286 |pages=95–101 |doi=10.1016/j.ejogrb.2023.05.027 |pmid=37229964 |s2cid=258860996 |url=https://www.ejog.org/action/showPdf?pii=S0301-2115%2823%2900217-8 |access-date=27 November 2023|doi-access=free ))</ref>

[[File:Instructions for the collection of a genital swab for the detection of GBS from CDC.tif|thumb|Instructions for the collection of a genital swab for the detection of GBS]]
These swabs should be placed into a non-nutritive transport medium.<ref name="ASM 2020" /><ref name="Verani 2010" /> When feasible, specimens should be refrigerated and sent to the laboratory as soon as possible.<ref name="ASM 2020" /><ref name="Verani 2010" />
Appropriate transport systems are commercially available, and in these transport media, GBS can remain viable for several days at room temperature. However, the recovery of GBS declines over one to four days, especially at elevated temperatures, which can lead to false-negative results.<ref name="ASM 2020" /><ref name="Verani 2010" /><ref name="Rosa 2005">((cite journal | vauthors = Rosa-Fraile M, Camacho-Muñoz E, Rodríguez-Granger J, Liébana-Martos C | title = Specimen storage in transport medium and detection of group B streptococci by culture | journal = Journal of Clinical Microbiology | volume = 43 | issue = 2 | pages = 928–930 | date = February 2005 | doi = 10.1128/jcm.43.2.928-930.2005 | pmid = 15695709 | pmc = 548104 ))</ref>

'''Additional and Early Method of Screening-Bacteriuria'''

The US Preventive Services Task Force and ACOG recommend routine urine screening for all pregnant women early in their pregnancies, even in the absence of urinary symptoms, in order to detect asymptomatic bacteriuria.
As with UTIs, ''any'' asymptomatic bacteriuria (not just GBS) cases with high CFU/mL values have also been shown to induce pyelonephritis, low birth weight, and preterm deliveries.<ref>((cite journal | vauthors = Owens DK, Davidson KW, Krist AH, Barry MJ, Cabana M, Caughey AB, et al | title = Screening for Asymptomatic Bacteriuria in Adults: US Preventive Services Task Force Recommendation Statement | journal = JAMA | volume = 322 | issue = 12 | pages = 1188–1194 | date = September 2019 | pmid = 31550038 | doi = 10.1001/jama.2019.13069 | s2cid = 202746652 | doi-access = free ))</ref>

Therefore, treatment of these asymptomatic cases at the time of diagnosis with antibiotics is just as important as treating symptomatic UTIs in pregnancy in order to reduce these risks. In addition to cases of GBS UTI and asymptomatic GBS bacteriuria with high CFU/mL, pregnant women with asymptomatic GBS bacteriuria, even with low CFU/mL counts at any time during the pregnancy, should receive IAP during birth to protect the newborn, regardless of the results of the recto-vaginal screen later in pregnancy.This is because GBS bacteriuria, even asymptomatic, at any CFU/mL is an indication of heavy ano-genital colonization.<ref name="ACOG 2020" /><ref>((Cite journal |last1=Smaill |first1=Fiona M. |last2=Vazquez |first2=Juan C. |date=2019-11-25 |title=Antibiotics for asymptomatic bacteriuria in pregnancy |journal=The Cochrane Database of Systematic Reviews |volume=2019 |issue=11 |pages=CD000490 |doi=10.1002/14651858.CD000490.pub4|pmid=31765489 |pmc=6953361 ))</ref>

==== Culture methods ====
Samples (vaginal, rectal, or vaginorectal swabs) should be inoculated into a selective enrichment broth, ([[Todd Hewitt broth]] with selective antibiotics, enrichment culture). This involves growing the samples in a selective enriched broth medium to improve the viability of the GBS and simultaneously impairing the growth of other naturally occurring bacteria. Appropriate enrichment broths, commercially available, are Todd-Hewitt with gentamicin and nalidixic acid (Baker broth), or with colistin and nalidixic acid (Lim broth).<ref name="Rosa 2017" /><ref name="ASM 2020" />

After incubation (18–24 hours, 35-37&nbsp;°C), the enrichment broth is subcultured overnight in blood agar plates and GBS-like colonies (big colonies, 3-4 millimeters diameter, surrounded by narrow zone of hemolysis)<ref name="Rosa 2017" /><ref name="ASM 2020" /> are identified by the CAMP test or using latex agglutination with GBS antiserum or MALDI-TOF.<ref name="Rosa 2017" /><ref name="ASM 2020" /><ref name="Verani 2010" /><ref name="ACOG 2020" />

In the UK, this is the method described by the Public Health England's [[UK Standards for Microbiology Investigations]]<ref name="SMI B 58">((cite web |last1=UK Gov. |title=SMI B 58: detection of carriage of group B streptococci. Updated 2018 |date=26 June 2018 |url=https://www.gov.uk/government/publications/smi-b-58-processing-swabs-for-group-b-streptococcal-carriage |access-date=28 February 2021))</ref>

After incubation, the enrichment broth can also be subcultured to [[granada medium]] agar where GBS grows as pinkish-red colonies, and further identification test are not required<ref name="Rosa 2017" /><ref name="Rosa-Fraile 1999" /><ref name="gragar1">((cite journal | vauthors = Gil EG, Rodríguez MC, Bartolomé R, Berjano B, Cabero L, Andreu A | title = Evaluation of the Granada agar plate for detection of vaginal and rectal group B streptococci in pregnant women | journal = Journal of Clinical Microbiology | volume = 37 | issue = 8 | pages = 2648–2651 | date = August 1999 | pmc = 85303 | doi = 10.1128/JCM.37.8.2648-2651.1999 | pmid = 10405415 ))</ref><ref name="gragar2">((cite journal | vauthors = Claeys G, Verschraegen G, Temmerman M | title = Modified Granada Agar Medium for the detection of group B Streptococcus carriage in pregnant women | journal = Clinical Microbiology and Infection | volume = 7 | issue = 1 | pages = 22–24 | date = January 2001| url=https://www.clinicalmicrobiologyandinfection.com/action/showPdf?pii=S1198-743X%2814%2963728-9| pmid = 11284939 | doi = 10.1046/j.1469-0691.2001.00156.x  | doi-access = free ))</ref> or to chromogenic agars, where GBS grows as coloured colonies.<ref name="Verani 2010" />
Nevertheless, GBS-like colonies that develop in chromogenic media should be confirmed as GBS using additional reliable tests to avoid mis-identification.<ref name="Rosa 2017" />

Inoculating directly the vaginal and rectal swabs or the vaginorectal swab in a plate of an appropriate culture medium (blood agar, granada medium or chromogenic media) is also possible. However, this method (bypassing the selective enrichment broth step) can lead to some false-negative results, and this approach should be taken only in addition to, and not instead of, inoculation into selective broth.<ref name="Verani 2010" />

Today, in the UK, the detection of GBS colonization using the enrichment broth technique is not offered from most laboratories serving the NHS. However, the implementation of this test seems to be a viable option.  At present, culture for GBS (using enriched culture medium) at 35–37 weeks to define an at-risk group of women appears to be the most cost-effective strategy.<ref name=pmid17848402/><ref name="Kaambwa 2010"/>

The [[charitable organization]] [[Group B Strep Support]] have published a list of hospitals in the UK that offer<!-- hospitals offer --> the detection of GBS using the enrichment broth culture method (enrichment culture medium, ECM).<ref name="Where can I get the ECM test?">((cite web|last1=Where can I get the ECM test?|title=ECM Testing|url=http://gbss.org.uk/who-we-are/testing-for-gbs/ecm-test-where-how/|website=Group B Strep Support|access-date=22 November 2023))</ref> This test is also available privately from around £35 per test for a home-testing pack, and it is offered by private clinics.<ref name="Where can I get the ECM test?" /> The test is also available privately, for a UK-wide postal service.<ref>((cite web|url=http://www.medisave.co.uk/group-b-streptococcus-screening-test-p-7896.html?gclid=CP7Z276TwbICFQfMtAod0mUAGQ|title=Group B Streptococcus Screening Test|work=Medisave UK Ltd|access-date=20 November 2023))</ref>
<ref name="The Doctors Lab">((cite web|title=Testing for Group B Streptococcus|url=http://www.tdlpathology.com/test-information/new-tests/testing-for-group-b-streptococcus|website=The Doctors Laboratory|access-date=20 November 2021))</ref>

====Point-of-care testing, POCT====
No current culture-based test is both accurate enough and fast enough to be recommended for detecting GBS once labour starts. Plating of swab samples requires time for the bacteria to grow, meaning that this is unsuitable to be used as an intrapartum [[point-of-care test]] (POCT or bedside testing).<ref name="ACOG 2020" />

Alternative methods to detect GBS in clinical samples (as vaginorectal swabs) rapidly have been developed, such are the methods based on [[nucleic acid amplification tests]], (NAAT) such as [[polymerase chain reaction]] (PCR) tests, and DNA [[hybridization probe]]s. These tests can also be used to detect GBS directly from broth media, after the enrichment step, avoiding the subculture of the incubated enrichment broth to an appropriate agar plate.<ref name="Rosa 2017" /><ref name="Verani 2010" /><ref name="Buchan 2015">((cite journal | vauthors = Buchan BW, Faron ML, Fuller D, Davis TE, Mayne D, Ledeboer NA | title = Multicenter clinical evaluation of the Xpert GBS LB assay for detection of group B Streptococcus in prenatal screening specimens | journal = Journal of Clinical Microbiology | volume = 53 | issue = 2 | pages = 443–448 | date= February 2015 | doi = 10.1128/jcm.02598-14 | pmid = 25411176 | pmc = 4298547 ))</ref>

Testing women for GBS colonization using vaginal or rectal swabs at 35–37 weeks of gestation and culturing them in an enriched media is not as rapid as a PCR test that would check whether the pregnant woman is carrying GBS at delivery. PCR tests would allow starting IAP on admission to the labour ward in those women for whom it is not known if they are GBS carriers.<ref name="Verani 2010" />

PCR testing for GBS carriage could, in the future, be sufficiently accurate to guide IAP. However, the PCR technology to detect GBS must be improved and simplified to make the method cost-effective and fully useful as a [[point-of-care test]]. These tests still cannot replace antenatal culture for the accurate detection of GBS.<ref name="Verani 2010" /><ref name="ACOG 2020" /><ref name="Koliwer-Brandl 2023">((cite journal |last1=Koliwer-Brandl H, Nil A, Birri J, Sachs M, Zimmermann R, Zbinden R, Balsyte D |title=Evaluation of two rapid commercial assays for detection of Streptococcus agalactiae from vaginal samples |journal=Acta Obstet Gynecol Scand. |date=2023 |volume=102 |issue=4 |pages=450–456 |doi=10.1111/aogs.14519 |pmid=36772902 |pmc=10008276 ))</ref><ref name="Daniels 2009">((cite journal | vauthors = Daniels J, Gray J, Pattison H, Roberts T, Edwards E, Milner P, Spicer L, King E, Hills RK, Gray R, Buckley L, Magill L, Elliman N, Kaambwa B, Bryan S, Howard R, Thompson P, Khan KS | display-authors = 6 | title = Rapid testing for group B streptococcus during labour: a test accuracy study with evaluation of acceptability and cost-effectiveness | journal = Health Technology Assessment | volume = 13 | issue = 42 | pages = 1–154, iii–iv | date = September 2009 | pmid = 19778493 | doi = 10.3310/hta13420 | doi-access = free ))</ref>

POCT for detection of GBS carriers requires additionally that maternity units should provide 24/7 laboratory means required to perform rapid testing.
Nevertheless, point-of-care testing may be used for women who present in labor with an unknown GBS status and without risk factors for ascertaining the use of IAP.<ref name="ACOG 2020" />

===Missed opportunities of prevention===
The important factors for successful prevention of GBS-EOD using IAP and the universal screening approach are:((citation needed|date=December 2020))
* Reach most pregnant women for antenatal screens
* Proper sample collection
* Using an appropriate procedure for detecting GBS
* Administering a correct IAP to GBS carriers

Most cases of GBS-EOD occur in term infants born to mothers who screened negative for GBS colonization and in preterm infants born to mothers who were not screened, though some false-negative results observed in the GBS screening tests can be due to the test limitations and to the acquisition of GBS between the time of screening and delivery. These data show that improvements in specimen collection and processing methods for detecting GBS are still necessary in some settings.  False-negative screening test, along with failure to receive IAP in women delivering preterm with unknown GBS colonization status, and the administration of inappropriate IAP agents to penicillin-allergic women account for most missed opportunities for prevention of cases of GBS-EOD.<ref name="Pulver 2009">((cite journal | vauthors = Pulver LS, Hopfenbeck MM, Young PC, Stoddard GJ, Korgenski K, Daly J, Byington CL | title = Continued early onset group B streptococcal infections in the era of intrapartum prophylaxis | journal = Journal of Perinatology | volume = 29 | issue = 1 | pages = 20–25 | date = January 2009 | pmid = 18704032 | doi = 10.1038/jp.2008.115 | doi-access = free ))</ref>

GBS-EOD infections presented in infants whose mothers had been screened as GBS culture-negative are particularly worrying, and may be caused by incorrect sample collection, delay in processing the samples, incorrect laboratory techniques, recent antibiotic use, or GBS colonization after the screening was carried out.<ref name="Gimenez 2015" /><ref name="Pulver 2009"/><ref name="Melin 2011">((cite journal | vauthors = Melin P | title = Neonatal group B streptococcal disease: from pathogenesis to preventive strategies | journal = Clinical Microbiology and Infection | volume = 17 | issue = 9 | pages = 1294–1303 | date = September 2011 | url=https://www.clinicalmicrobiologyandinfection.com/action/showPdf?pii=S1198-743X%2814%2961207-6    | doi = 10.1111/j.1469-0691.2011.03576.x  | pmid = 21672083 | doi-access = free ))</ref><ref name="Berardi 2010">((cite journal | vauthors = Berardi A, Lugli L, Baronciani D, Rossi C, Ciccia M, Creti R, Gambini L, Mariani S, Papa I, Tridapalli E, Vagnarelli F, Ferrari F | display-authors = 6 | title = Group B Streptococcus early-onset disease in Emilia-romagna: review after introduction of a screening-based approach | journal = The Pediatric Infectious Disease Journal | volume = 29 | issue = 2 | pages = 115–121 | date = February 2010 | pmid = 19915512 | doi = 10.1097/inf.0b013e3181b83cd9 | s2cid = 31548613 ))</ref><ref name="Schrag & Verani 2013">((cite journal | vauthors = Schrag SJ, Verani JR | title = Intrapartum antibiotic prophylaxis for the prevention of perinatal group B streptococcal disease: experience in the United States and implications for a potential group B streptococcal vaccine | journal = Vaccine | volume = 31 | issue = Suppl 4 | pages = D20–D26 | date = August 2013 | doi = 10.1016/j.vaccine.2012.11.056 | pmid = 23219695 | url = https://zenodo.org/record/1259435 ))</ref>

===Epidemiology===

In 2000–2001, the reported overall incidence of GBS infection in newborn babies in the UK was 0.72 per 1,000 live births, 0.47 per 1,000 for GBS-EOD and 0.25 per 1,000 for GBS-LOD. Very marked variations were observed, the incidence in Scotland was 0.42 per 1,000, whilst in Northern Ireland, it was 0.9 per 1,000 live births.<ref name="Heath 2004">((cite journal | vauthors = Heath PT, Balfour G, Weisner AM, Efstratiou A, Lamagni TL, Tighe H, O'Connell LA, Cafferkey M, Verlander NQ, Nicoll A, McCartney AC | display-authors = 6 | title = Group B streptococcal disease in UK and Irish infants younger than 90 days | journal = Lancet | volume = 363 | issue = 9405 | pages = 292–294 | date = January 2004 | pmid = 14751704 | doi = 10.1016/s0140-6736(03)15389-5 | s2cid = 22371160 ))</ref><ref name="Doare 2013">((cite journal | vauthors = Le Doare K, Heath PT | title = An overview of global GBS epidemiology | journal = Vaccine | volume = 31 | pages = D7-12 | date = August 2013 | issue = Suppl 4 | pmid = 23973349 | doi = 10.1016/j.vaccine.2013.01.009 ))</ref>

Nevertheless, it may be a serious underestimation of the real incidence of GBS infections in newborns. A plausible explanation of this is that a considerable number of infants with probable GBS-EOD had negative cultures as a result of a previous maternal antibiotic treatment that inhibits the growth of GBS in blood and cerebrospinal fluid cultures, but does not mask clinical symptoms.<ref name="Brigtsen 2015">((cite journal | vauthors = Brigtsen AK, Jacobsen AF, Dedi L, Melby KK, Fugelseth D, Whitelaw A | title = Maternal Colonization with Group B Streptococcus Is Associated with an Increased Rate of Infants Transferred to the Neonatal Intensive Care Unit | journal = Neonatology | volume = 108 | issue = 3 | pages = 157–163 | date = 2015 | pmid = 26182960 | doi = 10.1159/000434716 | s2cid = 24711146 ))</ref><ref name="Carbonell 2008">((cite journal | vauthors = Carbonell-Estrany X, Figueras-Aloy J, Salcedo-Abizanda S, de la Rosa-Fraile M | title = Probable early-onset group B streptococcal neonatal sepsis: a serious clinical condition related to intrauterine infection | journal = Archives of Disease in Childhood. Fetal and Neonatal Edition | volume = 93 | issue = 2 | pages = F85–F89 | date = March 2008 | pmid = 17704105 | doi = 10.1136/adc.2007.119958 | s2cid = 10300571 ))</ref>

Data collected prospectively for neonates that required a septic screen in the first 72 hrs of life in the UK 1n 2003, indicated a combined rate of definite and probable GBS-EOD infection of 3.6 per 1,000 live births.<ref>((cite journal | vauthors = Luck S, Torny M, d'Agapeyeff K, Pitt A, Heath P, Breathnach A, Russell AB | title = Estimated early-onset group B streptococcal neonatal disease | journal = Lancet | volume = 361 | issue = 9373 | pages = 1953–1954 | date = June 2003 | pmid = 12801740 | doi = 10.1016/S0140-6736(03)13553-2 | s2cid = 33025300 ))</ref>

Another study on the epidemiology of invasive GBS infections in England and Wales, reported a rise in the incidence of GBS-EOD between 2000 and 2010 from 0.28 to 0.41 per 1,000 live births. Rates of GBS-LOD also increased between 1991 and 2010 from 0.11 to 0.29 per 1,000 live births in England and Wales.<ref name="Lamagni 2013">((cite journal | vauthors = Lamagni TL, Keshishian C, Efstratiou A, Guy R, Henderson KL, Broughton K, Sheridan E | title = Emerging trends in the epidemiology of invasive group B streptococcal disease in England and Wales, 1991-2010 | journal = Clinical Infectious Diseases | volume = 57 | issue = 5 | pages = 682–688 | date = September 2013 | pmid = 23845950 | doi = 10.1093/cid/cit337 | doi-access = free ))</ref>
   
In the past, the incidence of GBS-EOD ranged from 0.7 to 3.7 per thousand live births in the US,<ref name="Edwards 2011" /> and from 0.2 to 3.25 per thousand in Europe.<ref name="Rodriguez-Granger 2012" />
In 2008, after widespread use of antenatal screening and intrapartum antibiotic prophylaxis, the [[Centers for Disease Control and Prevention]] in the United States <!-- (CDC) --> reported an incidence of 0.28 cases of GBS-EOD per thousand live births in the US.
From 2006 to 2015 the incidence of GBS EOD decreased from 0.37 to 0.23 per thousand live births in the US.<ref name="Nanduri_2019" /><ref name="Baker 2013 Vacc">((cite journal | vauthors = Baker CJ | title = The spectrum of perinatal group B streptococcal disease | journal = Vaccine | volume = 31 | issue = Suppl 4 | pages = D3–D6 | date = August 2013 | pmid = 23973344 | doi = 10.1016/j.vaccine.2013.02.030 ))</ref>
In contrast with GBS-EOD, the incidence of GBS-LOD has remained stable in the US at 0.31 per 1000 live births from 2006 to 2015.<ref name="Nanduri_2019" />
In 2021, in the United States the CDC reported an incidence of 0.21
per 1,000 live births of GBS-EOD and of 0.23 per thousand live births of GBS-LOD. In 2021 had been estimated  a total of 1970 deaths ((0.59/100,000 population) in US caused by GBS neonatal infections.<ref name="Bacterial Core Surveillance 2021" />

In Spain, the incidence of GBS vertical sepsis declined by 73.6%, from 1.25/1,000 live births in 1996 to 0.33/1,000 in 2008.<ref name="Lopez Sastre 2009">((cite journal| vauthors = Lopez Sastre J, Fernandez Colomer B, Coto Cotallo Gil D | collaboration = Grupo de Hospitales Castrillo |title=Neonatal Sepsis of Vertical Transmission. An epidemiological study from the "Grupo de Hospitales Castrillo"|journal=Early Human Development|date=2009|volume=85|issue=10|pages=S100|doi=10.1016/j.earlhumdev.2009.08.049))</ref>
In Spain in the Barcelona area between 2004 and 2010, the incidence of GBS-EOD was 0.29 per thousand living newborns, with no significant differences along the years. The mortality rate was 8.16%.<ref name="Gimenez 2015"/><ref name="Amdreu Sanfeliu 2003">((cite journal | vauthors = Andreu A, Sanfeliu I, Viñas L, Barranco M, Bosch J, Dopico E, Guardia C, Juncosa T, Lite J, Matas L, Sánchez F, Sierr M | display-authors = 6 | title = [Decreasing incidence of perinatal group B streptococcal disease (Barcelona 1994-2002). Relation with hospital prevention policies] | journal = Enfermedades Infecciosas y Microbiologia Clinica | volume = 21 | issue = 4 | pages = 174–179 | date = April 2003 | pmid = 12681128 | doi = 10.1016/s0213-005x(03)72913-9 ))</ref>
The "Grupo de Hospitales Fundación Castrillo"has also reported in 2018 in Spain an incidence of GBS-EOD of 0.17/1000 live births and 0,05/1000 of GBS LOD.<ref name="Rosa-Alos 2022">((cite journal |last1=Rosa-Fraile M, Alós JI. |title=Group B Streptococcus neonatal infections, the ongoing history. |journal=Enferm Infecc Microbiol Clin |date=2022 |volume=40 |issue=7 |pages=349–352 |doi=10.1016/j.eimce.2022.01.002|pmid=35906029 ))</ref>

[[File:Incidence GBS-EOD in Spain-Castrillo group.tif|thumb|Falling incidence of GBS-EOD in Spain (Castrillo Group of Hospitals)]]

In France since 2001, a rapid decrease in the incidence of the neonatal GBS infections has also been reported after widespread use of IAP, from 0.7 to 0.2 per 1,000 births between 1997 and 2006. 
The incidence of GBS-EOD infections has been reported to be 0.2 per 1000 live births in 2011.<ref>((cite journal | vauthors = Albouy-Llaty M, Nadeau C, Descombes E, Pierre F, Migeot V | title = Improving perinatal Group B streptococcus screening with process indicators | journal = Journal of Evaluation in Clinical Practice | volume = 18 | issue = 4 | pages = 727–733 | date = August 2012 | pmid = 21414110 | doi = 10.1111/j.1365-2753.2011.01658.x ))</ref><ref name="Sikias 2022">((cite journal |last1=Sikias P, Biran V, Foix-L'Hélias L, Plainvert C, Boileau P, Bonacorsi S; EOS study group. |title=Early-onset neonatal sepsis in the Paris area: a population-based surveillance study from 2019 to 2021 |journal=Arch Dis Child Fetal Neonatal |date=2022 |volume=108 |issue=2 |pages=114–120 |doi=10.1136/archdischild-2022-324080 |pmid=35902218 |pmc=9985718 ))</ref>

Since 2012 the incidence of neonatal GBS infection has been estimated as 0.53 per 1,000 births in the European region, 0.67 in America, and 0.15 in Australasia. Countries reporting no use of IAP had a 2.2-fold higher incidence of GBS-EOD compared with those reporting any use of IAP.<ref name="Edmond 2012" /><ref name="Doare 2013"/>

Estimates of the incidence of GBS-EOD per 1,000 births differs among countries, Japan 0.09, Panama 0,58, Hong Kong 0,76, and 2.35 in the Dominican Republic. Overall, rates are highest in Africa and lowest in Asia. The estimate of the global incidence of GBS LOD is 0.26 cases per 1,000 live births.<ref name="Raabe 2019">((cite journal | vauthors = Raabe VN, Shane AL | title = Group B ''Streptococcus'' (''Streptococcus agalactiae'') | journal = Microbiology Spectrum | volume = 7 | issue = 2 | date = March 2019 | pmid = 30900541 | doi = 10.1128/microbiolspec.GPP3-0007-2018 | pmc = 6432937 ))</ref>
It has been appraised that GBS infections cause at least 409.000 maternal/fetal/infant cases and 147.000 stillbirths and infant deaths worldwide annually.<ref name="Seale 2017">((cite journal | vauthors = Seale AC, Bianchi-Jassir F, Russell NJ, Kohli-Lynch M, Tann CJ, Hall J, Madrid L, Blencowe H, Cousens S, Baker CJ, Bartlett L, Cutland C, Gravett MG, Heath PT, Ip M, Le Doare K, Madhi SA, Rubens CE, Saha SK, Schrag SJ, Sobanjo-Ter Meulen A, Vekemans J, Lawn JE | display-authors = 6 | title = Estimates of the Burden of Group B Streptococcal Disease Worldwide for Pregnant Women, Stillbirths, and Children | journal = Clinical Infectious Diseases | volume = 65 | issue = suppl_2 | pages = S200–S219 | date = November 2017 | pmid = 29117332 | pmc = 5849940 | doi = 10.1093/cid/cix664 ))</ref>
Recently, it has been estimated that 20 million pregnant women were colonised in the world by GBS in 2020 and 400,000 children developed early-onset or late-onset GBS. Over
90,000 newborn deaths were calculated to occur, most of then in Sub-Saharan countries.<ref name="Proma Goncalvez 2023">((cite journal |last1=Proma P., Goncalvez B.P., Le Doare k., Lawn E. |title=20 million pregnant women with group B streptococcus carriage: consequences, challenges, and opportunities for prevention |journal=Curr Opin Pediatr |date=2023 |volume=35 |issue=2 |pages=223–230 |doi= 10.1097/MOP.0000000000001223     
 |pmid=36749143 |pmc=9994794 ))</ref>

The following are estimates of the chances that a baby will be infected with a GBS neonatal infection if no preventive measures are taken and no other risk factors are present:<ref name="Benitz 1999">((cite journal | vauthors = Benitz WE, Gould JB, Druzin ML | title = Risk factors for early-onset group B streptococcal sepsis: estimation of odds ratios by critical literature review | journal = Pediatrics | volume = 103 | issue = 6 | pages = e77 | date = June 1999 | pmid = 10353974 | doi = 10.1542/peds.103.6.e77 | doi-access = free ))</ref>
* One in 1,000 where the woman is not a known GBS carrier
* One in 400 where the woman carries GBS during the pregnancy
* One in 300 where the woman carries GBS at delivery
* One in 100 where the woman had a previous baby infected with GBS

If a woman who carries GBS is given IAP during labour, the baby's risk is reduced significantly:
* One in 8,000 where the mother carries GBS during pregnancy;
* One in 6,000 where the mother carries GBS at delivery; and
* One in 2,200 where the mother has previously had a baby infected with GBS

===Guidelines===

====United Kingdom====

===== Royal College of Obstetricians and Gynaecologists (RCOG)=====

The [[Royal College of Obstetricians and Gynaecologists]] (RCOG) first issued their Green Top Guideline No 36 "Prevention of early onset neonatal Group B streptococcal disease" in 2003.
This guideline clearly stated: "Routine bacteriological screening of all pregnant women for antenatal GBS carriage is not recommended, and vaginal swabs should not be taken during pregnancy unless there is a clinical indication to do so." But, "Intrapartum antibiotic prophylaxis should be offered if GBS is detected on a vaginal swab in the current pregnancy."((citation needed|date=December 2023))
Nevertheless, this guideline uses minimum incidence figures from a study undertaken in 2000–2001,<ref>((cite journal | vauthors = Heath PT, Balfour G, Weisner AM, Efstratiou A, Lamagni TL, Tighe H, O'Connell LA, Cafferkey M, Verlander NQ, Nicoll A, McCartney AC | display-authors = 6 | title = Group B streptococcal disease in UK and Irish infants younger than 90 days | journal = Lancet | volume = 363 | issue = 9405 | pages = 292–294 | date = January 2004 | pmid = 14751704 | doi = 10.1016/S0140-6736(03)15389-5 | s2cid = 22371160 ))</ref> so it could not only have underestimated the true incidence of GBS infection, but it could also have underestimated the risks to babies from GBS infection.
GBS infection in babies has increased in England, Wales, and Northern Ireland since 2003 (when the guideline was introduced). Voluntarily reported cases from the Communicable Disease Report/Health Protection Agency show 0.48 cases per 1,000 live births in 2003, and this figure increased to 0.64 per 1,000 in 2009.<ref name="Health Protection Report 2011">((cite web|last1=Health Protection Report Vol. 5 No. 46 – 18 November 2011 ·|title=Pyogenic and non-pyogenic streptococcal bacteraemia, England, Wales and Northern Ireland: 2010|url=https://webarchive.nationalarchives.gov.uk/ukgwa/20140714084352/http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1317131482001
|website=Health Protection Report|access-date=1 December 2023))</ref>

In 2007, the RCOG published the findings of their audit to evaluate practice in the UK obstetric units against their recommendations. The audit started out by comparing international guidelines for prevention of GBS-EOD: highlighting the fact that, in contrast to the UK and New Zealand guidelines, most of the other countries recommended identifying women for IAP by offering effective tests to all pregnant women.  The audit reviewed hospitals' protocols against GBS infection in newborns. Of the 161 UK units, which submitted their protocol, four units did not even have a protocol for GBS, of those that did, 35% did not mention the 2003 RCOG guideline, and only a minority of units had protocols entirely consistent with the guideline.((citation needed|date=June 2020))

Further UK research published in 2010 looked at the opportunities for prevention of GBS-EOD following the introduction of the RCOG guideline.  They found that, in the 48 cases of GBS during 2004 to 2007 (0.52/1,000 live births), only 19% of the mothers in whom risk factors were present were given adequate IAP.  The researchers stated: "if all women with risk factors received prophylaxis, 23 cases (48%) may have been prevented.((citation needed|date=December 2023))

The 2003 RCOG guideline was reviewed in July 2012 and again in September 2017 with substantial changes.<ref name="onlinelibrary.wiley.com"/>

The second and final audit report into GBS (Audit of current practice in preventing GBS EOD in the UK) has been published. As a result of the audit, the RCOG have recommended that the national guidelines for preventing GBS infection in newborns should be updated.

In the UK, the [[RCOG]] still does not recommend bacteriological screening of all pregnant women for antenatal GBS carriage in its 2017 guidelines, although it does state that women who tested positive in a previous pregnancy and the baby was well should be offered the option of testing and being offered intrapartum antimicrobial prophylaxis or having the IAP without testing.<ref name="RCOG 2017 Guidelines" />

Nevertheless, it is stated that if GBS carriage is detected incidentally or by intentional testing, women should be offered IAP. And that all pregnant women should be provided with an appropriate information leaflet about GBS and pregnancy (published in December 2017).<ref name="UK GBS leaflet">((cite web |last1=RCOG-GBSS |title=Information for you. Group B Streptococcus (GBS) in pregnancy and newborn babies |url=https://www.rcog.org.uk/media/xtmfktbh/pi-gbs-pregnancy-newbornnewlogo21.pdf |access-date=2 December 2023))</ref>

Instead, women are treated according to their risk in labour. IAP is offered to women in labout where GBS has been found from their urine or vaginal/rectal swabs taken during the pregnancy, and to women who have previously had a baby with GBS disease. Immediate induction of labour and IAP should be offered to all women with prelabour rupture of membranes at 37 weeks of gestation or more, to women whose membranes are ruptured more than 18 hours and to those who have fever in labour.((citation needed|date=June 2022)) Women who are pyrexial in labour should be offered broad-spectrum antibiotics including an antibiotic appropriate for preventing EOD-GBS.<ref name="RCOG 2017 Guidelines" />

=====NICE guidelines=====
The UK's [[National Institute for Health and Care Excellence]] (NICE) does not recommend routine testing for GBS, stating: "Pregnant women should not be offered routine antenatal screening for group B streptococcus because evidence of its clinical and cost effectiveness remains uncertain."<ref name="NICE 2008">((cite web|last1=Screening for infections.1.8.9 Group B streptococcus|title=Antenatal care for uncomplicated pregnancies.NICE guidelines [CG62] : March 2008|url=https://www.nice.org.uk/guidance/CG62/chapter/1-Guidance#screening-for-infections|website=NICE National Institute for Health and Care Excellence|date=26 March 2008 |access-date=27 November 2019))</ref>

This guideline was updated in 2021 nevertheless screening and testing for GBS was outside of this new guideline's sphere. 
However, the guideline states that "At the first antenatal (booking) appointment (and later if appropriate), discuss and give information on .... infections that can impact on the baby in pregnancy or during birth (such as group B streptococcus, herpes simplex and cytomegalovirus)"<ref>((Cite web |title=Recommendations ((!)) Antenatal care ((!)) Guidance ((!)) NICE |url=https://www.nice.org.uk/guidance/ng201/chapter/Recommendations#information-and-support-for-pregnant-women-and-their-partners |access-date=2022-05-21 |website=www.nice.org.uk|date=19 August 2021 ))</ref>
Nevertheless, the NICE Neonatal Infection guideline states: "Offer antibiotics during labour to women who:
* are in pre-term labour '''or'''
* have group B streptococcal colonisation, bacteriuria or infection during the current pregnancy '''or'''
* have had group B streptococcal colonisation, bacteriuria or infection in a previous pregnancy, and have not had a negative test for group B streptococcus by enrichment culture or PCR on a rectovaginal swab samples collected between 35 and 37 weeks' gestation or 3-5 weeks before the anticipated delivery date in the current pregnancy '''or'''
* have had a previous baby with an invasive group B streptococcal infection '''or'''
* have a clinical diagnosis of chorioamnionitis. '''[2021]'''".<ref>((Cite web |title=Recommendations ((!)) Neonatal infection: antibiotics for prevention and treatment ((!)) Guidance ((!)) NICE |url=https://www.nice.org.uk/guidance/ng195/chapter/Recommendations#preventing-early-onset-neonatal-infection-before-birth |access-date=2022-05-21 |website=www.nice.org.uk|date=20 April 2021 ))</ref>

===== National Screening Committee =====
The [[UK National Screening Committee]]'s current policy position on GBS is: "screening should not be offered to all pregnant women. This policy was reviewed in 2012, and despite receiving 212 responses, of which 93% advocated screening, the NSC has decided to not recommend antenatal screening.<ref name="UK National Screening Committee">((cite web |last1=UK National Screening Committee |title=Current UK NSC from the UK National Screening Committee (UK NSC). |url=https://legacyscreening.phe.org.uk/screening-recommendations.php |access-date=4 March 2021))</ref>
((citation needed|date=December 2023))

This decision was strongly criticized by the charity Group B Strep Support as ignoring both the wishes of the public and the rising incidence rates of GBS infection in the UK.<ref>((cite web|url=http://us4.campaign-archive2.com/?u=6599c26deb03ac68f3446cccc&id=4816108c26|title=Leading baby charity devastated by decision not to introduce life saving screening of pregnant women.2012|work=campaign-archive2.com|access-date=4 March 2021))</ref>

====United States====

Recommendations for IAP to prevent perinatal GBS disease were issued in 1996 by the CDC.  In these guidelines, the use of one of two prevention methods was recommended: either a risk-based approach or a culture-based screening approach.<ref name="CDC 1996" /> The CDC issued updated guidelines in 2002; these guidelines recommended the universal culture-based screening of all pregnant women at 35–37 weeks' gestation to optimize the identification of women who must receive IAP. CDC also recommended that women with unknown GBS colonization status at the time of delivery be managed according to the presence of intrapartum risk factors. Because of this strategy, the US has seen a major reduction in the incidence of GBS-EOD.<ref name="CDC 2002">((cite journal|last1=Centers for Disease Control and Prevention- CDC|first1=MMWR|title=Prevention of Perinatal Group B Streptococcal Disease Revised Guidelines from CDC. 2002|journal=Morbidity and Mortality Weekly Report|date=2002|volume=51-RR11|pages=1–22|url=https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5111a1.htm|access-date=4 March 2021))</ref>

The CDC issued updated guidelines again in 2010, however, the foundations of prevention in the CDC's 2010 guidelines remained unchanged.<ref name="Verani 2010" /> The following were the main additions in the 2010 guidelines:
* Expanded options for laboratory detection of GBS include the use of pigmented media and PCR assays.
* A revised colony count threshold was set for laboratories to report GBS in the urine of pregnant women.
* Revised algorithms for GBS screening and use of IAP for women with threatened preterm delivery include one algorithm for preterm labor and one for preterm premature rupture of membranes.
* Recommendations for IAP agents are presented in an algorithm format in an effort to promote the use of the most appropriate antibiotic for penicillin-allergic women.
* A minor change has been made to penicillin dosing to facilitate implementation in facilities with different packaged penicillin products.
* The neonatal management algorithm's scope was expanded to apply to all newborns.
* Management recommendations depend upon clinical appearance of the neonate and other risk factors such as maternal chorioamnionitis, adequacy of IAP if indicated for the mother, gestational age, and duration of membrane rupture.
* Changes were made to the algorithm to reduce unnecessary evaluations in well-appearing newborns at relatively low risk for GBS-EOD.

In 2018, the task of revising and updating the GBS prophylaxis guidelines were transferred from the CDC to [[American College of Obstetricians and Gynecologists|ACOG]], to the [[American Academy of Pediatrics]], AAP and to the [[American Society for Microbiology]], ASM.<ref name="ACOG 2020" /><ref name="CDC 2019">((cite web |last1=CDC |title=Prevention Guidelines. 2019 Guidelines Update. |url=https://www.cdc.gov/groupbstrep/guidelines/index.html|access-date=4 March 2021))</ref>

The ACOG committee issued an updated document on Prevention of Group B Streptococcal Early-Onset Disease in Newborns in 2019.<ref name="ACOG 2020" />

ACOG's guidance replaced the 2010 guidelines published by CDC.<ref name="Verani 2010" /> This document does not introduce important changes from the CDC guidelines. The key measures necessary for preventing neonatal GBS early onset disease continue to be universal prenatal screening by culture of GBS from swabs collected from the lower vagina and rectum, correct collection and microbiological processing of the samples, and proper implementation of intrapartum antibiotic prophylaxis. It is also important to note that the ACOG recommended performing universal GBS screening between 36 and 37 weeks of gestation. This new recommendation provides a 5-week window<ref name="Yancey 1996" /> for valid culture results that includes births that occur up to a gestational age of at least 41 weeks.

In 2019, [[American Academy of Pediatrics]] (AAP) published a new clinical report—Management of Infants at Risk for GBS neonatal disease.<ref name="AAP Puopolo 2019" /> This AAP's Clinical Report replaces the 2010 guidelines published by CDC.<ref name="Verani 2010" />
ASM states that it is acceptable to use NAAT-based identification of GBS from enrichment broth (after 18-24-hour incubation) with high sensitivity, and that FDA-cleared commercial assays are available to perform the test.<ref name="ASM.org" />

However, direct-from-specimen NAATs is not recommended due to low sensitivity with high rates of false negative results.<ref name="ASM.org" /> Moreover, ACOG has a favorable view of the use of NAATs and states that NAATs from enrichment broth testing is reasonable, has higher sensitivity for detecting GBS than culture, and, therefore, a possibly better test.<ref name="ACOG 2020" />
This recommendation is based on data proving the valuable utility of the test.<ref>((cite journal | vauthors = Couturier BA, Weight T, Elmer H, Schlaberg R | title = Antepartum screening for group B Streptococcus by three FDA-cleared molecular tests and effect of shortened enrichment culture on molecular detection rates | journal = Journal of Clinical Microbiology | volume = 52 | issue = 9 | pages = 3429–3432 | date = September 2014 | pmid = 25009049 | pmc = 4313176 | doi = 10.1128/JCM.01081-14 | veditors = Carroll KC ))</ref>
 
Unlike ASM, ACOG also allows for the use of NAATs without the enrichment broth,<ref name="ACOG 2020" /> despite the high false negative rate, as a rapid (point-of-care) test for women who present in labor with unknown GBS status. However, both ASM and ACOG acknowledge that NAAT-based testing does not have the capability to provide the antibiotic susceptibility needed to identify the IAP regimen needed for women with a penicillin allergy.<ref name="ASM.org" /><ref name="ACOG 2020" />

====Other guidelines====
National guidelines in most countries advocate the use of universal screening of pregnant women late in pregnancy to detect GBS carriage and use of IAP in all colonized mothers. e.g. Canada,<ref name="Money">((cite journal | vauthors = Money D, Allen VM | title = N<sup>o</sup> 298 - Prévention de l'infection néonatale à streptocoques du groupe B d'apparition précoce | journal = Journal of Obstetrics and Gynaecology Canada | volume = 40 | issue = 8 | pages = e675–e686 | date = August 2018 | pmid = 30103892 | doi = 10.1016/j.jogc.2018.05.033 | s2cid = 51980587 ))</ref> Spain,<ref name="Alos 2012">((cite journal | vauthors = Alós Cortés JI, Andreu Domingo A, Arribas Mir L, Cabero Roura L, Cueto Lopez M, López Sastre J, Melchor Marcos JC, Puertas Prieto A, de la Rosa Fraile M, Salcedo Abizanda S, Sánchez Luna M, Sánchez Pérez MJ, Torrejón Cardoso R | display-authors = 6 | title = [Prevention of perinatal group B Streptococcal disease. Updated Spanish recommendations 2012] | journal = Revista Espanola de Quimioterapia | volume = 25 | issue = 1 | pages = 79–88 | date = March 2012 | pmid = 22488547 | url = https://seq.es/seq/0214-3429/25/1/alos.pdf | access-date = 25 November 2019 ))</ref> Switzerland,<ref name="Surbek 2007">((cite journal | title = [Prevention of neonatal infection with Streptococcus Group B. Expert correspondence no. 19 of 29th December 2006] | journal = Gynäkologisch-geburtshilfliche Rundschau | volume = 47 | issue = 2 | pages = 103–104 | date = 2007 | pmid = 17440274 | doi = 10.1159/000100342 | s2cid = 77887846 | author1 = Kommission Qualitätssicherung der Schweizerischen Gesellschaft für Gynäkologie und Geburtshilfe ))</ref> Germany,<ref name="Germany">((cite web |title=Prophylaxe der Neugeborenensepsis - frühe Form - durch Streptokokken der Gruppe B |url=https://gnpi.de/wp-content/uploads/2020/07/024-020l_S2k_Prophylaxe_Neugeborenensepsis_Streptokokken_2016-04.pdf |access-date=25 November 2023))</ref> Poland,<ref name="Pol 2008">((cite journal | vauthors = Kotarski J, Heczko PB, Lauterbach R, Niemiec T, Leszczyńska- Gorzelak B | title = Rekomendacje polskiego towarzystwa ginekologicznego dotyczące wykrywania nosicielstwa paciorkowców grupy B (GBS) u kobiet w ciąży i zapobiegania zakażeniom u noworodków | trans-title = Recommendations Polish Gynecological Society for the detection of carriers of GBS in pregnant women and prevent infections in newborns. | language = pl | journal = Ginekol Pol | date = 2008 | volume = 79 | pages = 221–223 | url =https://www.ptgin.pl/sites/scm/files/2021-09/02.2008%20-%20W%20TRAKCIE%20AKTUALIZACJI%20-%20Wykrywanie%20nosicielstwa%20GBS%20u%20kobiet%20w%20ci%C4%85%C5%BCy%20i%20zapobiegania%20zaka%C5%BCeniom%20u%20noworodk%C3%B3w.pdf))</ref> Czech Republic,<ref name="Czech 2013">((cite journal| vauthors = Měchurová A, Vlk R, Unzeitig V, Švihovec P, Mašata J | title = Diagnostika a léčba streptokoků skupiny B v těhotenství a za porodu–doporučený postup. | trans-title = Diagnosis and treatment of group B streptococci during pregnancy and childbirth – recommended procedure. | language = Czech | journal = Čes Gynek. | date = 2013 | volume = 78 | pages = 11–14 | url = https://www.porodniasistentky.info/wp-content/uploads/2016/08/p-2013-diagnostika-a-lecba-streptokoku-skupiny-b-v-tehotenstvi.pdf))</ref> France,<ref name="France 2001">((cite web| work = Agence Nationale d'Accreditation et d'Evaluation en Santé | trans-work = National Agency for Accreditation and Health Evaluation |title=Prévention anténatale du risque infectieux bactérien néonatal précoce | trans-title = Antenatal prevention of the risk of early neonatal bacterial infection | language = fr | date = 2001 |url=http://www.has-sante.fr/portail/upload/docs/application/pdf/prevention_antenatale_du_risque_infectieux_bacterien_-_rec.pdf|access-date=2 March 2021))</ref> Belgium,<ref name="Belgium 2003">((cite web|last1=Belgian Health Council|title=Prevention of perinatal group B streptococcal infections. Guidelines. 2003|url=https://orbi.ulg.ac.be/bitstream/2268/8652/1/GBS_CSH%20english%202003.pdf|archive-url=https://web.archive.org/web/20160304104930/https://orbi.ulg.ac.be/bitstream/2268/8652/1/GBS_CSH%20english%202003.pdf |access-date=25 November 2023|archive-date=4 March 2016 ))</ref> Argentina<ref name="Argentina Ley 26369">((cite web|access-date=27 November 2023|date=2008|language=es|title=Realización del examen de detección del estreptococo Grupo B Agalactiae, a todas las embarazadas con edad gestacional entre las semanas 35 y 37|url=https://e-legis-ar.msal.gov.ar/htdocs/legisalud/migration/html/7539.html#:~:text=LEY%2026369,rutinaria%20de%20control%20y%20prevenci%C3%B3n.))<!-- auto-translated by Module:CS1 translator --></ref> and Colombia<ref name=Colombia>((cite web|access-date=27 November 2023|date=2018|language=es|title=Resolución 3280|url=https://www.minsalud.gov.co/Normatividad_Nuevo/Resoluci%C3%B3n%20No.%203280%20de%2020183280.pdf))<!-- auto-translated by Module:CS1 translator --></ref>

In contrast, risk factor-based guidelines were issued (in addition to the UK <ref name="RCOG 2017 Guidelines" />) in the Netherlands,<ref name="Nederland">((cite web | work = Nederlandse Vereniging voor Obstetrie en Gynaecologie | trans-work = Dutch Association for Obstetrics and Gynaecology |date = 2008 | title = Preventie van neonatale groep-B-streptokokkenziekte (GBS-ziekte) Versie 2.0 | trans-title = Prevention of Neonatal Group B Streptococcal Disease (GBS-Disease) Version 2.0 | language = nl |url=http://www.med-info.nl/Richtlijnen/Gynecologie/Perinatologie/Preventie%20van%20neonatale%20groep-B-streptokokkenziekte%20(GBS-ziekte).pdf | publisher = Med-Info |access-date=25 November 2019))</ref>

The [[Royal Australian and New Zealand College of Obstetricians and Gynaecologists]] <!-- (RANZCOG) -->recommends that all maternity units   should have an established plan for prevention of neonata GBS disease. Nevertheless it is not recommend clearly one prevention strategy.<ref name="RANZCOG">((cite web |last1=Royal Australian and New Zealand College of Obstetricians and Gynaecologists. RANZCOG. |title=Streptococcus (GBS) in Pregnancy: Screening and Management. July 2019. |url=https://ranzcog.edu.au/wp-content/uploads/2022/05/Maternal-Group-B-Streptococcus-in-Pregnancy-Screening-and-Management.pdf|access-date=25 November 2023))</ref>

== Adults ==
GBS is also an important infectious agent able to cause invasive infections in adults. Serious life-threatening invasive GBS infections are increasingly recognized in the elderly and in individuals compromised by underlying diseases such as diabetes, [[cirrhosis]] and cancer.<ref name="Raabe 2019" /><ref name="Skoff 2009">((cite journal | vauthors = Skoff TH, Farley MM, Petit S, Craig AS, Schaffner W, Gershman K, Harrison LH, Lynfield R, Mohle-Boetani J, Zansky S, Albanese BA, Stefonek K, Zell ER, Jackson D, Thompson T, Schrag SJ | display-authors = 6 | title = Increasing burden of invasive group B streptococcal disease in nonpregnant adults, 1990-2007 | journal = Clinical Infectious Diseases | volume = 49 | issue = 1 | pages = 85–92 | date = July 2009 | pmid = 19480572 | doi = 10.1086/599369 | doi-access = free ))</ref>
GBS infections in adults include urinary tract infection, skin and soft-tissue infection ([[skin and skin structure infection]]) bacteremia without focus, osteomyelitis, meningitis and [[endocarditis]].<ref name="Edwards 2010" />
GBS infection in adults can be serious, and mortality is higher among adults than among neonates.<ref name="Raabe 2019" />

In general, penicillin is the antibiotic of choice for treatment of GBS infections. Erythromycin or clindamycin should not be used for treatment in penicillin-allergic patients unless susceptibility of the infecting GBS isolate to these agents is documented. [[Gentamicin]] plus penicillin (for [[antibiotic synergy]]) in patients with life-threatening GBS infections may be used.<ref name="Skoff 2009" /><ref name="Farley 2001">((cite journal | vauthors = Farley MM | title = Group B streptococcal disease in nonpregnant adults | journal = Clinical Infectious Diseases | volume = 33 | issue = 4 | pages = 556–561 | date = August 2001 | pmid = 11462195 | doi = 10.1086/322696 | doi-access = free ))</ref><ref name="Edwards 2005">((cite journal | vauthors = Edwards MS, Baker CJ | title = Group B streptococcal infections in elderly adults | journal = Clinical Infectious Diseases | volume = 41 | issue = 6 | pages = 839–847 | date = September 2005 | pmid = 16107984 | doi = 10.1086/432804 | doi-access = free ))</ref>

Invasive GBS infections in non-pregnant adults convey a rising hardship in most developed countries. Vaccination to prevent GBS infection could be a crucial approach to prevent GBS disease in adults.<ref name="Colin adults 2020">((cite journal |last1=Collin SM, Shetty N, Lamagni T. |title=Invasive Group B Streptococcus Infections in Adults, England, 2015-2016 |journal=Emerg Infect Dis. |date=2020 |volume=26 |issue=6 |pages=1174–1181 |doi=10.3201/eid2606.191141 |pmid=32441619 |pmc=7258460 ))</ref><ref name="Graux 2020">((cite journal | vauthors = Graux E, Hites M, Martiny D, Maillart E, Delforge M, Melin P, Dauby N | title = Invasive group B Streptococcus among non-pregnant adults in Brussels-Capital Region, 2005-2019 | journal = European Journal of Clinical Microbiology & Infectious Diseases | volume = 40 | issue = 3 | pages = 515–523 |date = March 2021 | doi = 10.1007/s10096-020-04041-0  | pmid = 32944894 | pmc = 7498195 ))</ref>

[[Toxic shock syndrome]] (TSS) is an acute multisystem life-threatening disease resulting in multiple organ failure.  The severity of this disease frequently warrants immediate medical treatment. TSS is caused primarily by some strains of ''[[Staphylococcus aureus]]'' and ''[[Streptococcus pyogenes]]'' that produce exotoxins. Nevertheless, invasive GBS infection can be complicated, though quite infrequently, by streptococcal toxic shock-like syndrome (STLS).<ref name="Al Akhrass">((cite journal | vauthors = Al Akhrass F, Abdallah L, Berger S, Hanna R, Reynolds N, Thompson S, Hallit R, Schlievert PM | display-authors = 6 | title = Streptococcus agalactiae toxic shock-like syndrome: two case reports and review of the literature | journal = Medicine | volume = 92 | issue = 1 | pages = 10–14 | date = January 2013 | doi = 10.1097/MD.0b013e31827dea11 | pmid = 23263717 | pmc = 5370747 ))</ref>

== Society and culture ==

July has been recognised as Group B Strep International Awareness Month,<ref name="GBBS - GBS month">((cite web |last1=Group B Strep Support (GBSS) |title=Home»Get Involved»Campaign»Group B Strep Awareness Month Group B Strep Awareness Month |date=24 June 2019 |url=https://www.dhd10.org/public-health-matters/july-is-group-b-strep-international-awareness-month/#:~:text=July%20is%20Group%20B%20Strep%20International%20Awareness%20Month.,babies%20during%20pregnancy%20through%20infancy. |access-date= 23 November 2023))</ref> a time when information about group B Strep aimed at families and health professionals is shared, predominantly in the UK and the US. In the UK, this is led by Group B Strep Support.<ref>((Cite web | url=http://www.gbss.org.uk | title=Home Page | work = Group B Strep Support ))</ref>

== Vaccine ==
Though the introduction of national guidelines to screen pregnant women for GBS carriage and the use of IAP has significantly reduced the burden of GBS-EOD disease, it has had no effect on preventing either GBS-LOD in infants or GBS infections in adults.<ref name=Jordan2008>((cite journal | vauthors = Jordan HT, Farley MM, Craig A, Mohle-Boetani J, Harrison LH, Petit S, Lynfield R, Thomas A, Zansky S, Gershman K, Albanese BA, Schaffner W, Schrag SJ | display-authors = 6 | title = Revisiting the need for vaccine prevention of late-onset neonatal group B streptococcal disease: a multistate, population-based analysis | journal = The Pediatric Infectious Disease Journal | volume = 27 | issue = 12 | pages = 1057–1064 | date = December 2008 | pmid = 18989238 | doi = 10.1097/inf.0b013e318180b3b9 | s2cid = 1533957 | url = https://zenodo.org/record/1234885 ))</ref>

Because of this, if an effective vaccine against GBS were available, it would be an effective means of controlling not only GBS disease in infants, but also infections in adults.<ref name="Graux 2020" />

There are a number of problems with giving [[antibiotic]]s to women in labor. Such antibiotic exposure risks included severe allergic reactions and difficulties screening pregnant women for GBS. If pregnant women could be given a vaccine against GBS, this could potentially prevent most cases of GBS without the need for antibiotics or screening.
[[Vaccination]] is considered an ideal solution to prevent not only early- and late-onset disease but also GBS infections in adults at risk.<ref name="Edwards-Rench 2016">((cite journal | vauthors = Edwards MS, Rench MA, Rinaudo CD, Fabbrini M, Tuscano G, Buffi G, Bartolini E, Bonacci S, Baker CJ, Margarit I | display-authors = 6 | title = Immune Responses to Invasive Group B Streptococcal Disease in Adults | journal = Emerging Infectious Diseases | volume = 22 | issue = 11 | pages = 1877–1883 | date = November 2016 | doi = 10.3201/eid2211.160914 | pmid = 27767008 | pmc = 5088039 ))</ref>
Development of GBS vaccines for maternal immunization has been identified as a priority by the [[World Health Organization]] on the basis of high unmet need.<ref name="WHO-GBS vaccine">((cite web |last1=World Health Organization |title=GBS vaccine research and development technical roadmap and WHO Preferred Product Characteristics |url=http://www.who.int/immunization/research/development/ppc_groupb_strepvaccines/en/ |archive-url=https://web.archive.org/web/20170422034607/http://www.who.int/immunization/research/development/ppc_groupb_strepvaccines/en/ |access-date=26 November 2023|archive-date=22 April 2017 ))</ref>

A GBS effective maternal vaccine could have a great effect on newborn morbidity and mortality. It has been estimated that this vaccine could prevent about 127,000 cases of GBS-EOD, 87,000 of GBS-LOD, 31,000 deaths and 18,000 cases of neuro-developmental impairment.<ref name="Procter 2023">((cite journal |last1=Procter SR, Gonçalves BP, Paul P, Chandna J, Seedat F, Koukounari A, Hutubessy R, Trotter C, Lawn JE, Jit M. |title=Maternal immunisation against Group B Streptococcus: A global analysis of health impact and cost-effectiveness |journal=PLOS Med. |date=2023 |volume=20 |issue=3 |pages=e1004068 |doi=10.1371/journal.pmed.1004068 |pmid=36917564 |pmc=10013922 |doi-access=free ))</ref>

As early as 1976,<ref name="Baker 1976" /> low levels of maternal antibodies against the GBS capsular polysaccharide were shown to be correlated with susceptibility to GBS-EOD and GBS-LOD. Maternal-specific antibodies, transferred from the mother to the newborn, were able to confer protection to babies against GBS infection.<ref name=Baker2014>((cite journal | vauthors = Baker CJ, Carey VJ, Rench MA, Edwards MS, Hillier SL, Kasper DL, Platt R | title = Maternal antibody at delivery protects neonates from early onset group B streptococcal disease | journal = The Journal of Infectious Diseases | volume = 209 | issue = 5 | pages = 781–788 | date = March 2014 | doi = 10.1093/infdis/jit549 | pmid = 24133184 | pmc = 3923540 ))</ref>
The [[capsular]] [[polysaccharide]] of GBS, which is an important virulence factor, is also an excellent candidate for the development of an effective vaccine.<ref name="Rodriguez-Granger 2012" /><ref name=Baker2014/><ref name="MadhiCutland2016">((cite journal | vauthors = Madhi SA, Cutland CL, Jose L, Koen A, Govender N, Wittke F, Olugbosi M, Meulen AS, Baker S, Dull PM, Narasimhan V, Slobod K | display-authors = 6 | title = Safety and immunogenicity of an investigational maternal trivalent group B streptococcus vaccine in healthy women and their infants: a randomised phase 1b/2 trial | journal = The Lancet. Infectious Diseases | volume = 16 | issue = 8 | pages = 923–934 | date = August 2016 | pmid = 27139805 | doi = 10.1016/S1473-3099(16)00152-3 ))</ref><ref name=Edwards-Gonik2013/>

GBS protein-based vaccines are also in development and are greatly promising as they will be able to protect against GBS infection of any serotype.<ref name="Graux 2020" /><ref name="Heath 2016"/><ref name="Song - Vaccine">((cite journal | vauthors = Song JY, Lim JH, Lim S, Yong Z, Seo HS | title = Progress toward a group B streptococcal vaccine | journal = Human Vaccines & Immunotherapeutics | volume = 14 | issue = 11 | pages = 2669–2681 | date = 2018 | doi = 10.1080/21645515.2018.1493326 | pmid = 29995578 | pmc = 6314413 ))</ref><ref name="RiaGupalova2018">((cite journal | vauthors = Gupalova T, Leontieva G, Kramskaya T, Grabovskaya K, Bormotova E, Korjevski D, Suvorov A | title = Development of experimental GBS vaccine for mucosal immunization | journal = PLOS ONE | volume = 13 | issue = 5 | pages = e0196564 | year = 2018 | doi = 10.1371/journal.pone.0196564 | pmid = 29727446 | pmc = 5935385 | doi-access = free | bibcode = 2018PLoSO..1396564G ))</ref><ref name="Carreras-Abad 2020">((cite journal | vauthors = Carreras-Abad C, Ramkhelawon L, Heath PT, Le Doare K | title = A Vaccine Against Group B ''Streptococcus'': Recent Advances | journal = Infection and Drug Resistance | volume = 13 | pages = 1263–1272 | date = 2020 |url=https://www.dovepress.com/getfile.php?fileID=57728| doi = 10.2147/IDR.S203454| pmid = 32425562 | pmc = 7196769 |access-date=26 November 2023 | doi-access = free ))</ref><ref name="Dominguez 2022">((cite journal |last1=Dominguez K, Randis TM. |title=Toward the development of a protein-based group B Streptococcus vaccine. |journal=Cell Rep Med. |date=2022 |volume=3 |issue=2 |pages=10.1016/j.xcrm.2022.100536 |doi=10.1016/j.xcrm.2022.100536 |pmid=35243427 |pmc=8861943 ))</ref>

At present, the licensing of GBS vaccines is difficult because of the challenge in conducting clinical trials in humans due to the low incidence of GBS neonatal diseases.<ref name="Rodriguez-Granger 2012" /><ref name="Edwards-Gonik2013">((cite journal | vauthors = Edwards MS, Gonik B | title = Preventing the broad spectrum of perinatal morbidity and mortality through group B streptococcal vaccination | journal = Vaccine | volume = 31 | issue = Suppl 4 | pages = D66–D71 | date = August 2013 | pmid = 23200934 | doi = 10.1016/j.vaccine.2012.11.046 ))</ref><ref name="Nuccitelli 2015">((cite journal | vauthors = Nuccitelli A, Rinaudo CD, Maione D | title = Group B Streptococcus vaccine: state of the art | journal = Therapeutic Advances in Vaccines | volume = 3 | issue = 3 | pages = 76–90 | date = May 2015 | doi = 10.1177/2051013615579869| pmid = 26288735 | pmc = 4530403 ))</ref>

Nevertheless, though research and clinical trials for the development of an effective vaccine to prevent GBS infections are underway, no vaccine is available as of 2023.<ref name="Heath 2016">((cite journal | vauthors = Heath PT | title = Status of vaccine research and development of vaccines for GBS | journal = Vaccine | volume = 34 | issue = 26 | pages = 2876–2879 | date = June 2016 | pmid = 26988258 | doi = 10.1016/j.vaccine.2015.12.072 | doi-access = free ))</ref><ref name="Carreras-Abad 2020" /><ref name="Davies - Vaccine">((cite journal | vauthors = Davies HG, Carreras-Abad C, Le Doare K, Heath PT | title = Group B Streptococcus: Trials and Tribulations | journal = The Pediatric Infectious Disease Journal | volume = 38 | issue = 6S Suppl 1 | pages = S72–S76 | date = June 2019 | url= https://journals.lww.com/pidj/fulltext/2019/06001/group_b_streptococcus__trials_and_tribulations.16.aspx |doi = 10.1097/INF.0000000000002328| pmid = 31205250 | s2cid = 189943251 |access-date=26 November 2023| doi-access = free ))</ref><ref name ="Mahdi 2023">((cite journal | vauthors = Madhi SA | title = Potential for Maternally Administered Vaccines for Infant Group B Streptococcus. | journal = New England Journal of Medicine | volume = 389 | issue = 3 | pages = 215–227 | date = June 2023|doi=10.1056/NEJMoa2116045| pmid = 37467497 | s2cid = 259995252 | doi-access = free ))</ref>

As of Winter 2023, there are two clinical development stage vaccines for the prevention of GBS invasive disease. Pfizer's hexavalent GBS vaccine [PF-06760805], '''GBS6''' is a CRM197 conjugated polysaccharide approach containing the 6 most prominent GBS serotypes worldwide.<ref name ="Buurman 2019">((cite journal | vauthors = Buurman ET | title = A Novel Hexavalent Capsular Polysaccharide Conjugate Vaccine (GBS6) for the Prevention of Neonatal Group B Streptococcal Infections by Maternal Immunization | journal = J Infect Dis | volume = 220 | issue = 1 | pages = 105–115 | date = June 2019 | pmid = 30778554 | doi = 10.1093/infdis/jiz062 | pmc = 6548902 | doi-access = free))</ref>
The vaccine which is currently undergoing Phase 3 planning, may offer '' meaningful protection against invasive disease in newborns and young infants'' on the basis of its immunogenicity results in the Phase 2 study [NCT03765073] which were published in the New England Journal of Medicine.<ref name ="Mahdi 2023" />

Danish-based '''MinervaX''' ApS are also developing a protein-based GBS vaccine '''(GBS-NN/NN2)''' designed using fusions of highly immunogenic and protective protein domains from selected surface proteins of GBS (the Alpha-like protein family).<ref>MinervaX Corporate Website https://www.MinervaX.com/MinervaX-provides-clinical-update-on-its-maternal-gbs-vaccine/</ref> The vaccine, which has been shown to be safe and immunogenic in maternal populations, is also undergoing preparations for Phase 3 planning. MinervaX has also completed enrolment of its Phase 1 adult trial [NCT05782179] with first immunological readouts anticipated in Q4 2023. A recent global demand analysis for GBS vaccines estimated the potential market for maternal and adult GBS immunization to be $798m/yr and $2,023m/yr in 2034 respectively.<ref name="VacZine Analytics">((cite web |title=MarketVIEW: Group B Streptococcus vaccines |url=https://www.vaczine-analytics.com/products-marketviewVAMV008_GBS_vaccines_forecast.asp |website=VacZine Analytics |access-date=26 November 2023))</ref>

Other preclinical GBS vaccine programs are being pursued by the US-based biotech, Omniose and Inventprise.((citation needed|date=June 2022))

==Nonhuman infections==
GBS has been found in many mammals and other animals such as camels, dogs, cats, seals, dolphins, and crocodiles.<ref name=Delannoy2013>((cite journal | vauthors = Delannoy CM, Crumlish M, Fontaine MC, Pollock J, Foster G, Dagleish MP, Turnbull JF, Zadoks RN | display-authors = 6 | title = Human Streptococcus agalactiae strains in aquatic mammals and fish | journal = BMC Microbiology | volume = 13 | pages = 41 | date = February 2013 | doi = 10.1186/1471-2180-13-41| pmid = 23419028 | pmc = 3585737 | doi-access = free ))</ref>

===Cattle===
In cattle, GBS causes mastitis, an infection of the udder. It can produce an acute febrile disease or a subacute, more chronic disease. Both lead to diminishing milk production (hence its name: ''agalactiae'' meaning "no milk").<ref name="Keefe 1997">((cite journal |vauthors=Keefe GP |date=July 1997 |title=Streptococcus agalactiae mastitis: a review |journal=The Canadian Veterinary Journal |volume=38 |issue=7 |pages=429–437 |pmc=1576741 |pmid=9220132))</ref>
GBS can survive and persist in mammary glands of cows, by forming  biofilms.<ref name="Cheng 2022">((cite journal |last1=Cheng WN, Han SG. |title=Bovine mastitis: risk factors, therapeutic strategies, and alternative treatments - A review |journal=Asian-Australas J Anim Sci. |date=2020 |volume=33 |issue=11 |pages=1699–1713 |doi=10.5713/ajas.20.0156 |pmid=32777908 |pmc=7649072 ))</ref> 
Mastitis associated with GBS can have an important effect on the quantity and quality of milk produced, and is also associated with elevated somatic cell count and total bacteria count in the milk.
<ref name="Ruegg - Mastitis">((cite journal | vauthors = Ruegg PL | title = A 100-Year Review: Mastitis detection, management, and prevention | journal = Journal of Dairy Science | volume = 100 | issue = 12 | pages = 10381–10397 | date = December 2017 |url=https://www.journalofdairyscience.org/action/showPdf?pii=S0022-0302%2817%2931032-9| doi = 10.3168/jds.2017-13023 | pmid = 29153171 | s2cid = 6122209 |access-date=26 November 2023| doi-access = free ))</ref>
Outbreaks in herds are common, and as this is of major significance for the dairy industry.<ref name="Morales-Ubaldo">((cite journal |last1=Morales-Ubaldo AL, Rivero-Perez N, Valladares-Carranza B, Velázquez-Ordoñez V, Delgadillo-Ruiz L, Zaragoza-Bastida A. |title=Bovine mastitis, a worldwide impact disease: Prevalence, antimicrobial resistance, and viable alternative approaches |journal=Vet Anim Sci. |date=2023 |volume=21 |pages=100306 |doi=10.1016/j.vas.2023.100306 |pmid=37547227 |pmc=10400929 ))</ref>

Programs to reduce the impact of GBS have been enforced in many countries<ref name="Keefe 1997" />

===Fish===
GBS it is also an important pathogen in a diversity of fish species, leading to serious economic losses in many species of fish worldwide. GBS causes severe epidemics in farmed fish, causing sepsis and external and internal hemorrhages. GBS infection has been reported from wild and captive fish and has been involved in [[epizootics]] in many countries.<ref name=Evans2009>((cite journal | vauthors = Evans JJ, Klesius PH, Pasnik DJ, Bohnsack JF | title = Human Streptococcus agalactiae isolate in Nile tilapia (Oreochromis niloticus) | journal = Emerging Infectious Diseases | volume = 15 | issue = 5 | pages = 774–776 | date = May 2009 | doi = 10.3201/eid1505.080222| pmid = 19402966 | pmc = 2687030 ))</ref><ref name="FAO">((cite web |last1=Food and Agriculture Organization of the United Nations |title=RISK PROFILE Group B Streptococcus (GBS) Streptococcus agalactiae sequence type (ST) 283 in freshwater fish |url=https://www.fao.org/3/cb5067en/cb5067en.pdf |access-date=26 November 2023))</ref><ref name=LiuG2013>((cite journal | vauthors = Liu G, Zhang W, Lu C | title = Comparative genomics analysis of Streptococcus agalactiae reveals that isolates from cultured tilapia in China are closely related to the human strain A909 | journal = BMC Genomics | volume = 14 | pages = 775 | date = November 2013 | pmid = 24215651 | pmc = 3831827 | doi = 10.1186/1471-2164-14-775 | doi-access = free ))</ref>
Outbreaks of GBS in tilapia aquaculture can result in serious disease with mortalities of up to 80%.<ref name="FAO">((cite web |last1=Food and Agriculture Organization of the United Nations |title=RISK PROFILE Group B Streptococcus (GBS) Streptococcus agalactiae sequence type (ST) 283 in freshwater fish |url=https://www.fao.org/3/cb5067en/cb5067en.pdf |access-date=26 November 2023))</ref>

It has also been reported a human foodborne outbreak of invasive disease caused by consumption of GBS infected tilapia <ref name="FAO" />

Vaccines to protect fish against GBS infections are under development.<ref name="Li 2015">((cite journal | vauthors = Li LP, Wang R, Liang WW, Huang T, Huang Y, Luo FG, Lei AY, Chen M, Gan X | display-authors = 6 | title = Development of live attenuated Streptococcus agalactiae vaccine for tilapia via continuous passage in vitro | journal = Fish & Shellfish Immunology | volume = 45 | issue = 2 | pages = 955–963 | date = August 2015 | pmid = 26087276 | doi = 10.1016/j.fsi.2015.06.014 ))</ref><ref name="Zhang- Tilapia">((cite journal | vauthors = Zhang D, Gao Y, Li Q, Ke X, Liu Z, Lu M, Shi C | title = An effective live attenuated vaccine against Streptococcus agalactiae infection in farmed Nile tilapia (Oreochromis niloticus) | journal = Fish & Shellfish Immunology | volume = 98 | pages = 853–859 | date = March 2020 | pmid = 31751658 | doi = 10.1016/j.fsi.2019.11.044 | s2cid = 208226408 ))</ref><ref name="Yostawornkul">((cite journal |last1=Thompson KD, Rodkhum C, Bunnoy A, Thangsunan P, Kitiyodom S, Sukkarun Yostawornkul J, Yata T, Pirarat N. |title=Addressing Nanovaccine Strategies for Tilapia |journal=Vaccines |date=2023 |volume=11 |issue=8 |page=1356 |doi=10.3390/vaccines11081356 |pmid=37631924 |pmc=10459980 |doi-access=free ))</ref>

== References ==
((Reflist))

== External links ==
* [http://gbss.org.uk/ UK Group B Strep Association]
* [https://www.cdc.gov/groupbstrep/index.html CDC—Group B Strep (GBS)]

((Medical resources
|  DiseasesDB      =
|  ICD10           = ((ICD10|B|95|1|b|95)), ((ICD10|P|36|0|p|35))
|  ICD9            =
|  ICDO            =
|  OMIM            =
|  MedlinePlus     =
|  eMedicineSubj   = article
|  eMedicineTopic  = 229091
|  MeshID          =
))

((Gram-positive bacterial diseases))
((Certain conditions originating in the perinatal period))
((Diseases of maternal transmission))
((Vaccines))

[[Category:Health issues in pregnancy]]
[[Category:Streptococcal infections]]
[[Category:Infections specific to the perinatal period]]
[[Category:Neonatology]]
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