title: Mycobacterium fallax
text: # 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.
  