Mycobacterium fallax

Mycobacterium fallax

Description
Gram-positive, nonmotile and acid-fast rods (0.5 – 1µm 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 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.