2.1. CHARACTERISTICS OF THE MYCOBACTERIUM TUBERCULOSIS
Mycobacterium tuberculosis (МВТ) - facultative intracellular parasite. МВТ belongs to the family of Mycobacteriacae, of order Actinomycetalis, and genus Mycobacterium. The genus of Mycobacteriacae comprise more than 100 species, the majority of them are saprophytes widespread in the environment.
Etymologically, "mycobacterium" is derived from the Greek words "my-ces" for "fungus" and "bakterium" meaning small rod. The name "fungus" derives from the tendency of these microorganisms to spread diffusely over the surface of liquid medium in a mold-like growth pattern.
"Mycobacterium tuberculosis" that cause tuberculosis was discovered by the German scientist Robert Koch in the year 1882. Later several variants of mycobacterium (mycobacterium complex) were discovered that in certain situations (for example - immunodeficiency) can cause a disease resembling tuberculosis. The mycobacterium complex includes: M. tuberculosis (МВТ), М. bovis and its Bacilli Calmette-Guerin (BCG) variant - M. bovis BCG, M. africanum, M. microti, M. cannetii, M. pinnipedii, M. caprae. There is a high degree of genetic relatedness in this group.
Mycobacterium tuberculosis has the appearance of slender rods that sometimes show branching filamentous forms resembling fungal mycelium. Straight or slightly curved rod of about 3μm×0,3μm, occurs either in pairs or formation of plait-like congestions (cord-factor) (Fig. 2.1 a, b, see color inset).
The cord-factor. The lipids of the external membrane of МВТ determine its virulence and formation of plait-like congestions (cord-factor) in nutrient medium. Koch noted about cord-factor in his initial report on the etiological agent of tuberculosis. First of all cord-factor related with virulence of MBT and parallel growth (Fig. 2.1 b). Formation of plait-like congestions was subsequently observed to occur among other mycobacterial species of lesser or hav-