Mycobacterium fallax
Scientific classification
Domain:	Bacteria
Phylum:	Actinomycetota
Class:	Actinomycetia
Order:	Mycobacteriales
Family:	Mycobacteriaceae
Genus:	Mycobacterium
Species:	M. fallax
Binomial name
Mycobacterium fallax Lévy-Frébault, V. et al. 1983,[1] ATCC 35219

Mycobacterium fallax is a species of the phylum Actinomycetota (Gram-positive bacteria with high guanine and cytosine content, one of the dominant phyla of all bacteria), belonging to the genus Mycobacterium.

Description

Gram-positive, nonmotile and acid-fast rods (0.5 – 1 µm long) except for a small number (less than 20%) of cyanophil forms.

Colony characteristics

• Large, eugonic, buff coloured and rough colonies (Löwenstein-Jensen medium at 30 °C).
• Cauliflower-like morphology, resembling M. tuberculosis colonies. Cord formation at the edges of colonies (Middlebrook 7H10 agar at 30 °C).

Physiology

• Rapid growth at 30 °C, but not at 37 °C, on Löwenstein-Jensen or Middlebrook 7H10 media.^[1]
• Susceptible to ethambutol, rifampin and kanamycin.
• Resistant to isoniazid, pyrazinamide and streptomycin.

Differential characteristics

• Similarities to M. tuberculosis include colony morphology, thermolabile catalase, positive nitrate reductase; differences are negative reactions for niacin production and rapid growth at 30 °C.

Pathogenesis

• Not known. Biosafety level 1.

Type strain

• Isolated from environmental sources in France and the former Czechoslovakia. Strain ATCC 35219 = CCUG 37584 = CIP 81.39 = DSM 44179 = JCM 6405.