Bacteriologic investigation of nontuberculous mycobacteria (NTM) isolated from environmental samples from animal dwellings

Nontuberculous mycobacteria (NTM) from soil and water samples from animal dwellings were characterized by conventional and biochemical tests. Different decontamination methods were used in selective isolation of mycobacteria from soil and water samples. 3% sodium lauryl sulfate combined with 1% NaOH was found most suitable decontaminant for concentration of both soil and water samples. A total of 81 soil and 20 water samples were processed resulting in isolation of 65 mycobacterial strains consisting 57 rapidly growing and 8 slowly growing mycobacteria. The mycobacterial isolates were identified and characterized based on growth rate, pigmentation and biochemical tests. The distribution of mycobacterial isolates as per Runyon's classification was; Group II (Scotochromogenic) 3 isolates (4.6%), Group III (Non-chromogenic & slowly growing) 5 isolates (7.7%) and Group IV (Rapidly growing) 57 isolates (87.7%). The species-wise distribution of 65 mycobacteria was M. fortuitum 33 (50.8%), M. smegmatis 4 (6.2%), M. chelonae 3 (4.6%), M. abcessus 2 (3.1%), M. phlei 9 (13%), M. vaccae 6 (9.2%), M. avium complex 5 (7.7%) and M. gordonae 3 (4.6%). The mycobacteria isolated from soil included M. fortuitum - 30 (52.6%), M. phlei - 9 (15.8%), M. vaccae and M. avium complex - 5 (8.8%) each, M. smegmatis and M. chelonae - 3 (5.3% each) and M. abcessus - 2 (3.5%) while that from water samples included M. fortuitum - 3(37.5%), M. gordonae - 3 (37.5%), M. smegmatis - 1 (12.5%) and M. vaccae - 1 (12.5%). Most mycobacterial species isolated reacted uniformly in the key biochemical tests, variations were however noticed in M. fortuitum, M. chelonae, M. vaccae and M. avium complex for a few tests.