Occurrence and diversity of non-tuberculous mycobacteria among suspected and confirmed cases of pulmonary tuberculosis

Abstract

BACKGROUND: Non-tuberculous mycobacteria (NTM) may cause pulmonary disease that resembles tuberculosis (TB) and it may also coexist with Mycobacterium tuberculosis. Here, we aimed to study the occurrence and diversity of NTM among suspected and confirmed cases of TB. METHODS: During 2017–2018, we received 11,094 sputum samples, of which 4288 samples were from equal number of presumptive TB patients. The rest of 6866 samples were from known multidrug-resistant TB patients and at different months of treatment follow-up. All samples were subjected to liquid culture and recovered isolates were identified as M. tuberculosis complex (MTBC) or NTM based on microscopy and immunochromatograhic (MPT-64Ag) tests. NTM isolates were further speciated using commercial GenoType® Mycobacterium CM assay. RESULTS: A total of 2782 culture isolates were recovered, of which 2722 were MTBC and the rest 60 were considered as NTM. NTM was isolated both from presumptive and confirmed TB cases. NTM speciation could be achieved for 42 isolates; Mycobacterium intracellulare (50%) was identified as the most prevalent species, followed by Mycobacterium abscessus (23.8%), Mycobacterium fortuitum (16.7%) and others (9.5%). CONCLUSION: The proportion of NTM isolation among suspected/confirmed cases of pulmonary TB is low; however, if isolated, patients should be carefully evaluated for possible NTM disease. Molecular speciation of NTM is useful to provide rapid and precise diagnosis.