Identification and Genotyping of Mycobacterium tuberculosis Isolated From Water and Soil Samples of a Metropolitan City

BACKGROUND: The potential role of environmentalMycobacterium tuberculosisin the epidemiology of TB remains unknown. We investigated the transmission ofM tuberculosisfrom humans to the environment and the possible transmission ofM tuberculosisfrom the environment to humans. METHODS:A total of 1,500 samples were collected from three counties of the Tehran, Iran metropolitan area from February 2012 to January 2014. A total of 700 water samples (47%) and 800 soil samples (53%) were collected. Spoligotyping and the mycobacterial interspersed repetitive units-variable number of tandem repeats typing method were performed on DNA extracted from single colonies. Genotypes ofM tuberculosisstrains isolated from the environment were compared with the genotypes obtained from 55 patients with confirmed pulmonary TB diagnosed during the study period in the same three counties. RESULTS:M tuberculosiswas isolated from 11 of 800 soil samples (1%) and 71 of 700 water samples (10%). T family (56 of 82, 68%) followed by Delhi/CAS (11 of 82, 13.4%) were the most frequentM tuberculosissuperfamilies in both water and soil samples. Overall, 27.7% of isolates in clusters were related. No related typing patterns were detected between soil, water, and clinical isolates. The most frequent superfamily ofM tuberculosisin clinical isolates was Delhi/CAS (142, 30.3%) followed by NEW-1 (127, 27%). The bacilli in contaminated soil (36%) and damp water (8.4%) remained reculturable in some samples up to 9 months. CONCLUSIONS: Although the dominantM tuberculosissuperfamilies in soil and water did not correspond to the dominantM tuberculosisfamily in patients, the presence of circulating genotypes ofM tuberculosisin soil and water highlight the risk of transmission.