4.2 Cellular morphology and staining

Mycobacteria are nonmotile, noncapsulating, and nonspore forming rods measuring 0.2–0.6 μm by 1.0–10 μm with a slender, straight or slightly curved shape. The cell wall of mycobacteria contains a hydrophobic lipid layer, which includes mycolic acids, phosphatidylinositol, mannosides, phthiocerol dimycocerosates, isoprenoid lipids, glycerophospholipids, lipoarabinomannan, and trehalose mycolates and lipoglycans, which give the organism some unique characteristics:

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 homoge-

M. bovis exhibits strain variation in biochemical characteristics, which can be

M. bovis M. tuberculosis

Test Reaction

Sensitivity to thiophen-2-carboxylic acid hydrazide (TCH) + — Sensitivity isonicotinic acid hydrazide (INH) + + Niacin production — + Nitrate reduction — + Pyrazinamidase test +\* — Nicotinamidase test +\* — Amidase test — + Urease production + Variable Growth under microaerophilic environment + —

The main limitation of biochemical tests is that sufficient amounts of bacterial cells as well and several weeks of incubation are required. The other limitation is that unknown species of mycobacteria cannot be identified. The availability of more rapid methods such as molecular methods has therefore diminished the use of

In general, mycobacteria are inactivated by prolonged exposure to heat, direct sunlight, and dry conditions. They are killed by temperatures of 65°C and above for at least 30 minutes and UV light but are resistant to freezing for prolonged periods. Under ordinary temperatures, M. bovis can persist in slurry and soil for at least 6 months and can survive for long periods in buildings and transport vehicles under dark, cold, and moist conditions [29, 36, 37]. The high lipid and wax content makes mycobacteria less susceptible to many chemical agents and disinfectants. Chemicals such as quaternary ammonium compounds, hexachlorophene, and chlorhexidine have bacteriostatic effect while formaldehyde vapor, chlorine compounds, 70% ethanol, hydrogen peroxide alkaline glutaraldehyde, and 5% phenol have bactericidal effect. Although treatment of infected animals is not normally practiced, M. bovis is resistant to most antibiotics but sensitive to the drugs used in treatment of M. tuberculosis (rifampin, isoniazid, streptomycin (STR), and ethambutol). M. bovis subsp. bovis is resistant to pyrazinamide (PZA), a first-line TB treatment drug in humans [38]. This characteristic is relevant in the management of infection in humans and also useful in differentiating M. bovis from M. tuberculosis. Multi-drug resistant strains of M. bovis have been reported in

nous turbidity [33].

4.4 Biochemical properties

summarized as follows [28, 34, 35]:

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

\*Mycobacterium bovis subsp. caprae is negative.

4.5 Environmental, chemical, and drug resistance

biochemical tests.

many countries [39].

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