4.3 Cultural characteristics

Mycobacteria are obligate aerobes and require complex organic media for growth. Solid media such as the egg-based Lowenstein-Jensen, (L-J), Middlebrook 7H10, and Middlebrook 7H11 or liquid media such as Modified Middlebrook 7H9 broth are used. Like other MTBC members, M. bovis is a slow grower. On solid media, colonies are detectable 3–6 and up to 12 weeks of incubation at 37°C weeks depending on the concentration of inoculum [28]. Colonies are small, raised, rounded, off-white (bluff) in color, wrinkled surface, and with irregular margins [29]. Addition of pyruvate is reported to stimulate growth of M. bovis and glycerol, which favors growth of M. tuberculosis, is said to inhibit it [28, 30]. Other findings however, indicate that M. bovis can grow satisfactorily in media containing either substance [5]. Members of MTBC group, including M. bovis, are inhibited by paranitrobenzoic acid (PNB), a criteria used to differentiate the group from MOTTs [31, 32]. Growth in liquid media is faster since the organism is surrounded by the media and access to nutrients is more efficient. Growth appears as clumps or "cords." Addition of egg yolk to the growth medium enhances growth, due to the presence of

Diseases Caused by Bacteria in Cattle: Tuberculosis DOI: http://dx.doi.org/10.5772/intechopen.82051

phospholipids that are required for growth but synthetic phospholipids such as polyoxyethylene sorbate compounds (Tweens) can also be used, which also lower the tendency of the mycobacteria to aggregate, giving a diffuse homogenous turbidity [33].
