Mycobacterium genavense

Mycobacterium genavense

Description
A slow-growing subspecies of Mycobacterium.

Gram-positive, and nonmotile acid-fast coccobacilli (1.0µm x 2.0µm). No formation of spores, capsules or aerial hyphae.

Colony characteristics
 * Tiny, transparent, nonphotochromogenic and dysgonic colonies (on solid Middlebrook 7H11 medium MJ (Allied Laboratories).

Physiology
 * Slow, fastidious growth in liquid media within 3-12 weeks at 31°C, 37°C and 42°C, with slightly better growth at 45°C.
 * Primary cultures for isolation require liquid broth media such as BACTEC 12B medium, Middlebrook 7H9 medium.
 * Acid broth media such as,BACTEC pyrazinamidase test medium, may facilitate primary isolation.
 * No growth on standard solid media like Löwenstein-Jensen, unsupplemented Middlebrook 7H11 or Middlebrook 7H10 media.
 * Visible growth on solid Middlebrook 7H11 medium supplemented with MJ after inoculation with a broth culture within 3–9 weeks.
 * Susceptible to streptomycin and rifampicin
 * Resistant to isoniazid and ethambutol

Differential characteristics
 * Differentiation from other slowly growing mycobacteria by its fastidious growth.
 * Closely related to M. simiae by evaluation of 16S rDNA sequences.

Pathogenesis

 * Opportunistic pathogen. Clinically indistinguishable from generalised infections in patients with AIDS due to M. avium complex strains, but more related to gastro-intestinal disorders.
 * Most common cause of mycobacterial disease in parrots and parakeets.

Type Strain
Strain 2289 = ATCC 51234