Phylum Actinobacteria, Class Actinobacteria, Order Actinomycetales, Suborder Corynebacterineae, Family Mycobacteriaceae, Genus
Mycobacterium, Mycobacterium genavense Bottger et al. 1993.
Member of the Mycobacterium simiae complex.
Acid-fast rods, 1.0 x 2.0 μm, frequently occuring in clump. Nonspore-forming.
Noncapsulated. Aerial hyphae are not produced.
Colonies are tiny, transparent, non-photochromogenic, dysgonic. In older cultures
may appear variant eugonic colonies which are either dense and creamy or flat and
dry. Fastidious growth - does not grow on standard solid media used for the isolation
of mycobacteria, such as Lowenstein-Jensen, Middlebrook 7H10 agar, and
unsupplemented Middlebrook 7H11 agar. Primary isolation requires broth media
(Middlebrook 7H9 or 7H12) and 3-12 weeks incubation. Grows better in acid broth
media. When inoculated with a broth culture suspension, visible growth on
Middlebrook 7H11 agar supplemented with mycobactin J requires 3-9
weeks.Temperature range for growth is 25-42 ºC; optimal growth is at 42 ºC; does not
grow at 45 ºC.
Isolated from clinical specimens (blood, bone marrow, liver and intestine, lymph nodes, and spleen) from patients with AIDS. Also
isolated from pet birds. Resistant to thiophene-2-carboxylic acid hydrazide (TCH) (1 μg/ml), ethambutol (2 μg/ml) and isoniazid (1
μg/ml). Susceptible to rifampin (32 μg/ml) and streptomycin (8 μg/ml).
Opportunistic pathogen, affecting immune-suppressed organisms.
- John G. Magee and Alan C. Ward 2012. Family III. Mycobacteriaceae Chester 1897, 63AL in Bergey’s Manual of Systematic
Bacteriology, Volume Five The Actinobacteria, Part A, Michael Goodfellow & al. (editors), 312-375.
- Bottger EC, Hirschel B, Coyle MB. Mycobacterium genavense sp. nov. Int J Syst Bacteriol 1993; 43:841-843.
Positive results for heat-stable catalase (68°C), semi-quantitative catalase test, pyrazinamidase, and urease.
Negative results for arylsulfatase activity at 3, 7 and 10 days, nitrate reduction, niacin accumulation, and Tween 80 hydrolysis.
(c) Costin Stoica