Unknown variety of Staphylococcus. Gram-stained. Numbered ticks on the scale are 11 microns apart.
Staphylococcus (from the Greek: σταφυλή, staphylē, "bunch of grapes" and κόκκος, kókkos, "granule") is a genus of Gram-positivebacteria. Under the microscope they appear round (cocci), and form in grape-like clusters.[1]
The Staphylococcusgenus includes at least fourty species and nine sub-species.[2] Most are harmless and reside normally on the skin and mucous membranes of humans and other organisms. Found worldwide, they are a small component of soil microbial flora.[3]
Staphylococcus can cause a wide variety of diseases in humans and other animals through either toxin production or penetration. Staphylococcal toxins are a common cause of food poisoning, as it can grow in improperly-stored food items.
Classification
Assignment of a strain to the genus Staphylococcus requires that it is a Gram-positive coccus that forms clusters, produces catalase, has an appropriate cell wall structure (including peptidoglycan type and teichoic acid presence) and G + C content of DNA in a range of 30-40 mol%.
One of the most important phenotypical features used in the classification of staphylococci is their ability to produce coagulase, an enzyme that causes blood clot formation.
Coagulase-positive
Six species are currently recognised as being coagulase positive: S. aureus, S. delphini, S. hyicus, S. intermedius, S. lutrae,S. pseudintermedius and S. schleiferi subsp. coagulans.
S. aureus (formerly also called staph pyogenes) is coagulase-positive, meaning that they can produce coagulase. However, while the majority of S. aureus are coagulase-positive, some may be atypical in that they do not produce coagulase. S aureus is also catalase-positive (meaning that it can produce the enzyme catalase) and able to convert hydrogen peroxide (H2O2) to water and oxygen, which makes the catalase test useful to distinguish Staphylococci from Enterococci and Streptococci.
S. pseudintermedius inhabits and sometimes infects the skin of domestic dogs and cats. This organism, too, can carry the genetic material that imparts multiple bacterial resistance. It is rarely implicated in infections in humans, as a zoonosis.
In recent years, several other Staphylococcus species have been implicated in human infections, notably S. lugdunensis, S. schleiferi, and S. caprae.
Common abbreviations for coagulase-negative staphylococcus species are CoNS and CNS.
Taxonomy
More detailed taxonomic work has been done based on 16s rRNA sequences.[4] The staphylococci fall into 11 clusters:
S. aureus group - S. aureus, S. simiae
S. auricularis group - S. auricularis
S. caseolyticus group - S. caseolyticus
S. carnosus group - S. carnosus, S. condimenti, S. massiliensis, S. piscifermentans, S. simulans
S. epidermidis group - S. capitis, S. caprae, S. epidermidis, S. saccharolyticus
S. haemolyticus group - S. haemolyticus, S. hominis
S. hyicus-intermedius group - S. chromogenes, S. felis, S. delphini, S. hyicus, S. intermedius, S. lutrae, S. microti, S. muscae, S. pseudintermedius, S. rostri, S. schleiferi
S. lugdunensis group - S. lugdunensis
S. saprophyticus group - S. arlettae, S. cohnii, S. equorum, S. gallinarum, S. kloosii, S. nepalensis, S. saprophyticus, S. succinus, S. xylosus
S. sciuri group - S. lentus, S. pulvereri, S. sciuri, S. vitulus
S. simulans group - S. simulans
S. warneri group - S. pasteuri, S. warneri
A twelfth group - that of S. caseolyticus - has now been moved to a new genus Macrococcus the species of which are currently the closest known relatives of the Staphylococci.[5]
Biochemical identification
Staphylococcus species can be differentiated from other aerobic and facultative anaerobic gram positive cocci by several simple tests. Staphylococcus spp. are facultative anaerobes. Facultative anaerobes are capable of growth both aerobically and anaerobically. All species grow in the presence of bile salts and all are catalase positive. Growth also occurs in a 6.5% NaCl solution. On Baird Parker MediumStaphylococcus spp. show as fermentative, except for S. saprophyticus, which is oxidative. Staphylococcus spp. are resistant to Bacitracin (0.04 U resistance = <10mm zone of inhibition) and susceptible to Furazolidone (100μg resistance = <15mm zone of inhibition).
Further biochemical testing is needed to identify down to the species level.
Genomics and molecular biology
The first S. aureusgenomes to be sequenced were those of N315 and Mu50 in 2001. Many more complete S. aureus genomes have been submitted to the public databases, making S. aureus one of the most extensively sequenced bacteria. The use of genomic data is now widespread and provides a valuable resource for researchers working with S. aureus. Whole genome technologies such as sequencing projects and microarrays have shown there is an enormous variety of S. aureus strains. Each contains different combinations of surface proteins and different toxins. Relating this information to pathogenic behaviour is one of the major areas of staphylococcal research. The development of molecular typing methods has enabled the tracking of different strains of S. aureus. This may lead to better control of outbreak strains. A greater understanding of how the staphylococci evolve, especially due to the acquisition of mobile genetic elements encoding resistance and virulence genes is helping to identify new outbreak strains and may even prevent their emergence.[6]
External links
Staphylococcus genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
Staphylococcus Infection Pictures - Pictures of Staph Infections, MRSA, and the associated skin diseases caused by these infections.
^Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN0838585299. ((cite book)): |author= has generic name (help)
^Harris L.G, Foster S.J (editor) (2002). AN INTRODUCTION TO STAPHYLOCOCCUS AUREUS, AND TECHNIQUES FOR IDENTIFYING AND QUANTIFYING S. AUREUS ADHESINS IN RELATION TO ADHESION TO BIOMATERIALS: REVIEW (LE.uGr.o Hpaearrni sC eetl lasl a n d M a t e r i a l s V o l . 4 . 2 0 0 2 ( p a g e s 3 9 - 6 0 ) ed.). ((cite book)): |author= has generic name (help); Unknown parameter |.ISSN= ignored (help); line feed character in |title= at position 61 (help)
^Madigan M, Martinko J (editors). (2005). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN0131443291. ((cite book)): |author= has generic name (help)
^Takahashi T, Satoh I, Kikuchi N.(1999) Phylogenetic relationships of 38 taxa of the genus Staphylococcus based on 16S rRNA gene sequence analysis. Int. J. Syst. Bacteriol. 49 (2) 725-728
^Kloos WE, Ballard DN, George CG, Webster JA, Hubner RJ, Ludwig W, Schleifer KH, Fiedler F, Schubert K (1998) Delimiting the genus Staphylococcus through description of Macrococcus caseolyticusgen. nov., comb. nov. and Macrococcus equipercicussp. nov., and Macrococcus bovicussp. nov. and Macrococcus carouselicussp. nov. Int J Syst Bacteriol. 48 (3) 859-877
