The ?new? mycobacteria

Abstract

There are more than 90 identified species of the genus Mycobacterium, of which over 50 are implicated in human disease. Two species, Mycobacterium tuberculosis (tuberculosis) and Mycobacterium leprae (leprosy), are usually pathogens only of humans. Mycobacteria are extremely diverse and inhabit various similarly diverse ecological niches. The vast majority are environmental organisms, found naturally in waterways, soil and other environments. Mycobacterium spp. are encountered with increasing frequency as opportunistic pathogens of humans, due to increased levels of immunosuppression in the population, selection of these organisms by disinfection, and improved diagnostic techniques. Contention exists regarding an appropriate collective term for this group of organisms, but they will be referred to here as ?environmental mycobacteria?.