Mycobacterium microti
Cultural characteristics
Biochemical characters
Phylum Actinobacteria, Class Actinobacteria, Order Actinomycetales, Suborder Corynebacterineae, Family Mycobacteriaceae, Genus
Mycobacterium microti Reed 1957.
Member of the
Mycobacterium tuberculosis complex.

According to Riojas et al. (2018),
M. microti is a later heterotypic synonym of Mycobacterium tuberculosis (Zopf 1883) Lehmann and
Neumann 1896.

Old synonyms: "Mycobacterium muris", "Mycobacterium tuberculosis subsp. muris",
"Vole tubercle bacillus".
Acid-fast rods. Nonspore-forming. Nonmotile. Gram-stain-positive.
Colonial morphology is variable. No pigmentation. Optimum temperature is 37 ºC.
Primary growth on glycerol-free egg media in 28-60 days; may adapt to tolerance to
glycerol. Does not grow at 22, 25, 40 or 45 ºC, or on media supplemented with 5%
(w/v) NaCl or on MacConkey agar without crystal violet.
Originally isolated from a vole - field mouse (Microtus agrestis). In subsequent studies, M. microti was also detected in other mammalian
species, like the bank vole (
Clethrionomys glareolus), the wood mouse (Apodemus sylvaticus), the shrew (Sorex araneus), cats and
pigs, and a zoo llama (
Lama vicugna molina).
Susceptible to tiophene-2-carboxylic acid hydrazide (1 μg/ml), rifampin (25 μg/ml), hydroxylamine (500 μg/ml), ethambutol (5 μg/ml), and
isoniazid (1 μg/ml).
Causes naturally acquired generalized tuberculosis in voles. Local lesions are produced in calves, rabbits, and guinea pigs.
It is not considered to be a human pathogen, though infections in immune-suppressed individuals have been reported. Because it
was considered non-pathogenic to humans,
M. microti has been used as an experimental tuberculosis vaccine in trials in the United
Kingdom and in the Czech Republic.
  1. 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.
  2. Riojas MA, McGough KJ, Rider-Riojas CJ, Rastogi N, Hazbon MH. Phylogenomic analysis of the species of the Mycobacterium
    tuberculosis complex demonstrates that Mycobacterium africanum, Mycobacterium bovis, Mycobacterium caprae,
    Mycobacterium microti and Mycobacterium pinnipedii are later heterotypic synonyms of Mycobacterium tuberculosis. Int J Syst
    Evol Microbiol 2018; 68:324-332.
  3. Dick van Soolingen, Adri G. M. van der Zanden, Petra E. W. de Haas, Gerda T. Noordhoek, Albert Kiers, Norbert A. Foudraine,
    Francoise Portaels, Arend H. J. Kolk, Kristin Kremer, Jan D. A. van Embden. Diagnosis of Mycobacterium microti Infections
    among Humans by Using Novel Genetic Markers. Journal of Clinical Microbiology Jul 1998, 36 (7) 1840-1845.
  4. Tsukamura M. Numerical identification of slowly growing mycobacteria. Microbiol Immunol. 1985;29(11):1039‐1050. doi:10.1111/j.
  5. M. Tsukamura. Numerical Classification of Slowly Growing Mycobacteria. International Journal of Systematic Bacteriology, Oct.
    1976, p. 409-420.
  6. Stephen Berger 2019. GIDEON Guide to Medically Important Bacteria, eBook.
  7. Helgomar Raducanescu, Valeria Bica-Popii. Bacili Gram pozitivi asporogeni, acidorezistenti. Familia Mycobacteriaceae Chester
    1897. Genul Mycobacterium Lehman si Newmann 1896, in Bacteriologie Veterinara, Ed. Ceres 1986, 155-169.
Positive result for alpha-esterase, arylsulphatase (14 days), niacin production, nicotinamidase, pyrazinamidase and urea hydrolysis.

Negative results for arylsulphatase (3 days), catalase (inactivated at 68°C), semi-quantitative catalase test, beta-galactosidase, and
Tween 80 hydrolysis.
No utilization as sole carbon source of acetate, citrate, succinate, malate, pyruvate, benzoate, fumarate, glucose, fructose, sucrose
ethanol, and propanol.

Variable results for nitrate reduction.
(c) Costin Stoica
Culture media
Biochemical tests
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