Mycobacterium genavense

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

Description

Nonmotile, acid-fast coccobacilli (1.0 µm x 2.0 µm). 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

References

• Böttger et al. 1993. Mycobacterium genavense sp. nov. Int. J. Syst. Bacteriol., 43, 841–843.