Mycobacterium fallax
# Mycobacterium fallax

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.
* 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.
