Context: Nontuberculous Mycobacteria (NTM) are emerging pathogens causing both pulmonary and extrapulmonary infections in humans. The differentiation of Mycobacteria is very important as the treatment differs based on the species of these pathogens, including Mycobacterium tuberculosis (MTb). Aim: Identification of NTM to species level among acid-fast bacilli (AFB)-positive clinical specimens and to establish the clinical significance of the NTM isolated. Settings and Design: It was a prospective study conducted at the Department of Microbiology of a tertiary care teaching hospital in coastal Karnataka. Materials and Methods: All specimens positive for AFB by Ziehl-Neelsen’s (ZN) technique were subjected to culture on Lowenstein-Jensen (LJ) media. The isolates positive for M. tuberculosis by rapid immunochromatographic identification test for the M. tuberculosis complex were excluded, and the remaining isolates were identified by conventional biochemical tests and confirmed using line probe assay—Hain’s GenoType Mycobacterium CM/AS 96. Statistical Analysis Used: The demographic, clinical details of the patients isolated with NTM were collected and analyzed by frequency, percentage, Chi-square test, and Fisher’s exact test using SPSS software version 21.0. Results: During the study period, a total of 100 clinically suspected TB patients, whose specimens were positive for ZN stain, were included in the study. The female-to-male ratio was 1:2.03. The most common age group to have positive AFB was 31–45 years for age (30/100). Pulmonary cases accounted for 79% and 21% extrapulmonary cases. Culture on LJ media grew 91 MTb and 9 NTM. Five out of the 9 (55.5%) isolates were from pulmonary samples (bronchoalveolar lavage 3 and sputum 2), and all four extrapulmonary isolates were from abscesses and nonhealing wounds. All nine NTM isolates were rapid growers; six (66.6%) of them were identified as M. fortuitum , two (25%) as M. abscessus , and one of the isolates could not be speciated by both conventional and molecular methods. Species identification was confirmed using line probe assay: M. fortuitum was isolated from three BAL, two soft tissue abscess, and one from sputum, whereas M. abscessus was isolated one each from sputum and soft tissue abscess. One unidentified NTM from an abscess. Extremes of age (elderly and paediatric) were the most common risk factor (88.8%), followed by low socio-economic status (77.7%), diabetes mellitus (66.6%), and alcoholism (33.3%). The majority of the AFB-positive NTM cases (88.89%) were started on anti-tubercular therapy. Conclusion: The occurrence of NTM among AFB-positive samples was found to be 9% in our study population. Rapidly growing NTM, M. fortuitum , and M. abscessus were only isolated from the patients studied. Pulmonary infections accounted for the majority of the cases and were associated with extremes of age, low socioeconomic status, diabetes mellitus, and alcoholism. Prompt isolation and rapid speciation of NTM is very important for early initiation of appropriate antimycobacterial agents for better prognosis in patients.
Philip et al. (Thu,) studied this question.