Title: Non-Tuberculous Mycobacteria: An Emerging Clinical Problem

Abstract

Mycobacteria are aerobic organism that are non-sporulating, non-motile (M. marinum is an exception) and have a waxy, relatively impermeable cell wall consisting of arabinogalactan and mycolic acids. There are over 188 mycobacterial species. Mycobacteria have a high GC content (around 65%) and the ability to grow over a wide temperature range (25-53 C). They are largely environmental organisms (M. tuberculosis and M. leprae are exceptions) and are slowly growing bacteria (M. leprae cannot be cultured on artificial media) with a long generation time of approximately twenty hours.

The Genus Mycobacterium contains, two major human pathogens: Mycobacterium tuberculosis (MTB) and Mycobacterium leprae. The former is the major cause of the illness tuberculosis, the latter, the agent causing leprosy. Tuberculosis is acquired from another person via the aerial route and Leprosy is believed to be acquired by prolonged close contact from another infected person, although the route of infection is not clear. In addition to these two obligate human pathogens, the Genus also comprises the non-tuberculous mycobacteria (NTM’s). These organisms are opportunist human pathogens that are found in the environment and are acquired from the environment rather than by person to person contact, although there is some suspicion that M. abscessus may be transmitted person to person.¹ Recently, due in part to whole genome sequencing (WGS) many new species of NTM’s have been identified and their clinical relevance and microbiological features have been recorded.^2,3 Non-tuberculous mycobacteria are mainly found in soil and water, frequently living inside species of amoeba⁴ but can also be isolated from various animal species, either as colonisers or causing an infection and for vegetation, food and milk.

Keywords: nontuberculous, mycobacteria, review