Mycobacterium genavense is a slow-growing 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
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
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 Mycobacterium 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.