Isolation and characterization of Non tuberculous Mycobacteria from clinical specimens

INTRODUCTION: Non Tuberculous Mycobacteria commonly known as Atypical Mycobacteria are seen in the environment and have been isolated worldwide. The prevalence of NTM infections are increasing and the diagnosis is often difficult or unconvincing. Identification of isolates to the species level is important, as infections with different Mycobacterium species often require different management and pathogens must be distinguished from environmental NTM contaminants. AIM OF THE STUDY: To isolate and characterize different species of Non tuberculous Mycobacteria from various clinical specimens. MATERIALS AND METHODS: The study was conducted in patients of PSG hospitals with clinical suspicion of tuberculosis during the period of January 2013 –July 2014.Sputum,tracheal aspirate ,BAL, pus and tissue were obtained as specimens. NTMs were isolated and speciated by using conventional biochemical tests.Immunochromatography (TBcID test) test was used to differentiate NTM from M.tuberculosis. Comparative evaluation of a commercial niacin strip test kit (BBLTM TaxoTM TB NiacinTest Strips) with conventional niacin test was done. RESULTS: A total of 3050 samples were received and processed in Mycobacteriology laboratory during the study period. Incidence of NTM during the study period was found to be 1.3%. Out of 363 culture positive acid fast bacilli, 40 (11.01%) were found to be Non tuberculous Mycobacteria. Among them 67.5% and 32.5% were rapid growers and slow growers respectively. The most common NTM isolated was Mycobacterium fortuitum (27 %). CONCLUSION: The incidence of Non Tuberculous Mycobacteria was found to be 1.3%. The commercial niacin test kit and TBc ID test were found to be 100 % sensitive and specific and can be used as an alternative for rapid diagnosis of NTM