Mycobacterium bovis

Mycobacterium bovis

Mycobacterium bovis is a bovine occurring bacterium and causative agent of tuberculosis in cattle. Mycobacterium bovis can be transmitted to humans and other pets ( goats). Human infection occurs mainly by non- pasteurized milk, but it is in the industrialized countries has become very rare.

Mycobacterium bovis is not a separate species of the genus Mycobacterium, but a tribe within the so-called Mycobacterium tuberculosis complex from which it probably originated ten thousand years ago. Through years of repeated cultivation of M. bovis BCG the live vaccine (Bacillus Calmette- Guérin ) was created, a vaccine against tuberculosis caused by M. tuberculosis in humans.

The genome has been completely sequenced.

Features

Mycobacterium bovis is like all species and strains of Gram- positive Mycobacteriaceae. The fixed cells are rod-shaped and non-spore forming. The bacterium is acid proof, a typical feature of mycobacteria. Another important feature is the structure of the cell wall of all mycobacteria ( inter alia, a high lipid content, and content of wax-like substances, such as mycolic acids ). In the special cell wall structure, the resistance to various antibiotics and the acid strength is due. Acid-fast bacteria give to coloring dyes despite an acid treatment did not back off. A first identification can be made by the Ziehl- Neelsen staining. After staining the bacteria are treated with acid, leaving only the acid-fast bacteria stained. However, acid-proof, other distantly related bacteria such as species of Nocardia, Rhodococcus and Corynebacterium.

In all mycobacteria metabolism is chemoorganotroph and requires oxygen ( However, M. bovis still for a short time microaerobically after isolation ).

Mycobacterium bovis is an obligate pathogen, it is as well as Mycobacterium tuberculosis unable to reproduce outside of the host. However, the mycobacteria are very well protected by the special cell wall against external influences and can survive for a time outside of the host. In the feces of cattle they should be able to grow even after up to 13 days.

Differences to other mycobacteria

The polymerase chain reaction (PCR) is a good and often used method to distinguish mycobacteria from other Mycobacterium bovis. Furthermore, the various tribes morphological (visible in the cultures ) and biochemical differences. Cultures of Mycobacterium bovis show a smooth, feuchtglitzerndes appearance. With the addition of glycerol, the growth is weak. In contrast, the growth of M. tuberculosis is promoted by glycerol. The cultures appear to be more crumbly and dry. Mycobacterium tuberculosis is not nitrate reduction and formation of niacin, M. bovis.

Immediately after the cultivation, Mycobacterium bovis behaves microaerophilic, it grows best in environments with low oxygen content. After repeated culturing, the strains for normal growth (21%) required oxygen content and are then, like all other mycobacteria obligately aerobic. This is another difference from Mycobacterium tuberculosis, which is the best growth immediately after the culture with full oxygen content.

Tuberculosis in cattle

The transmission of Mycobacterium bovis in cattle takes place mostly through the air (droplet infection). The bacteria can also be included with infected food, milk or water.

Mycobacterium bovis can be transmitted to other animals such as cats, dogs, sheep, pigs and goats. The bovine tuberculosis may also occur in the zoos, M. bovis was isolated eg from leopards, lions and baboons.

In Germany control measures against bovine tuberculosis were carried out in the 50s, so that the cattle disease has been almost completely eradicated. Thus 38.5 % of the examined cattle were still infected in 1952, in 1967 only 0.09%. After eradication of bovine tuberculosis in industrialized countries no longer represents the beef itself the main source of infection dar. Rather, now is an infection of the bovine by pets (such as cats) or by wild animals the chief danger of the outbreak of bovine tuberculosis. Even the sick man to open tuberculosis is a not unimportant source of infection for cattle ( but this is not necessary then an infection with M. bovis ) ..

Relevance to humans

The bovine tuberculosis, known in English as " bovine TB" is also transferable to the people, and ranks among the zoonoses. Infection occurs ( as in cattle ) through the respiratory tract or by food intake, often by non- pasteurized milk. In the latter, the intestinal tuberculosis is triggered. The bovine tuberculosis is also of the people back to cattle back -transferable.

The introduction of the pasteurization of milk, the number of transfers fell sharply on the people. The triggered by Mycobacterium bovis tuberculosis hardly plays a role in the industrialized countries in the Third World countries (developing countries ), it is however still important. In an Argentinean study, two percent of the 448 studied cases of pulmonary tuberculosis infection with M. bovis could be traced; the bacterial strains involved were the same ones who also befell most cattle. In a Chinese study, however, revealed a prevalence of 0.34 percent of M. bovis disease cases.

The changes in the organs affected by the tuberculosis from Mycobacterium bovis are indistinguishable from those caused by M. tuberculosis distinguishable.

System

Within the genus Mycobacterium is Mycobacterium bovis and M. bovis BCG the " Mycobacterium tuberculosis complex " attributed.

The two subspecies ( subspecies ) Mycobacterium bovis subsp. bovis and Mycobacterium bovis subsp. caprae are no longer performed. The latter is then placed to the genus Mycobacterium caprae.

Synonyms for Mycobacterium bovis Mycobacterium tuberculosis typus are bovinus Lehmann & Neumann 1907, and Mycobacterium tuberculosis var bovis Bergey et al., 1934.

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