Mycobacteria are widespread in the environment. They occur in all animal species and have been detected in the environment, eg in soil, dust, straw or in sawdust and wood shavings. They can practically always be detected in the biologically active layer of the soil and in the sediment of surface and waste water samples. It has to be assumed that there are an estimated 102 to 105 Mycobacteria per gram soil. Mycobacteria are part of the normal flora in soil, surface water and waste water.
Mycobacteria as pathogens
There are many pathogenic and non-pathogenic Mycobacteria species. Some pathogenic species are zoonosis pathogens, ie bacteria which are transmitted from animals to humans and can cause serious diseases.
Based on their significance as pathogens in the development of diseases in humans and animals a rough subdivision of the Mycobacteria species can be made into “tuberculous” and “non-tuberculous” Mycobacteria. Significant Mycobacteria in terms of human and veterinary medicine are species which are very closely related but not identical and can cause the so-called classical tuberculosis in humans and animals. These are pathogens of the Mycobacterium tuberculosis complex and the species Mycobacterium (M.) tuberculosis, M. bovis, M. africanum, M. microti and M. canettii, M.caprae (also M. bovis ssp. caprae) and M. pinnipedi.
Mycobacteria species which can cause tuberculosis-like changes – so-called mycobacteriosis – are allocated to the Mycobacterium avium intracellulare complex (MAIC) with the species M. avium ssp. avium, M. avium ssp. hominissuis, M. avium ssp. intracellulare, M. avium ssp. silvaticum and M. avium ssp. Paratuberculosis.
Mycobacteria are immobile short to coccoid rods and can be gram-stained. Due to their high stability vis a vis acids they can also be stained using special methods such as Ziehl-Neelsen and can be distinguished from other bacterial species. Based on the growth of Mycobacteria species under laboratory conditions a subdivision into slowly and rapidly growing mycobacteria is made; some species are highly demanding in terms of cultivation and only difficult to cultivate.