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. 2015 Apr;147(4):1094-1102.
doi: 10.1378/chest.14-0960.

Identification and genotyping of Mycobacterium tuberculosis isolated from water and soil samples of a metropolitan city

Ali Akbar Velayati  1 , Parissa Farnia  1 , Mohadese Mozafari  1 , Donya Malekshahian  1 , Amir Masoud Farahbod  1 , Shima Seif  1 , Snaz Rahideh  1 , Mehdi Mirsaeidi  2
Affiliations

Identification and genotyping of Mycobacterium tuberculosis isolated from water and soil samples of a metropolitan city

Ali Akbar Velayati et al. Chest. 2015 Apr.

Abstract

Background: The potential role of environmental Mycobacterium tuberculosis in the epidemiology of TB remains unknown. We investigated the transmission of M tuberculosis from humans to the environment and the possible transmission of M tuberculosis from 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 of M tuberculosis strains 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 tuberculosis was 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 frequent M tuberculosis superfamilies 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 of M tuberculosis in 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 dominant M tuberculosis superfamilies in soil and water did not correspond to the dominant M tuberculosis family in patients, the presence of circulating genotypes of M tuberculosis in soil and water highlight the risk of transmission.

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Figures

Figure 1 –
Figure 1 –
Water and soil sampling locations in Tehran metropolitan areas.
Figure 2 –
Figure 2 –
Dendrogram of soil and water Mycobacterium tuberculosis strains, which shows clustered and single strains. MIRU-VNTR = mycobacterial interspersed repetitive units-variable number of tandem repeats; UPGMA = unweighted pair group method with arithmetic mean.
Figure 3 –
Figure 3 –
Radial tree of M tuberculosis for clinical isolates and soil and water isolates. See Figure 2 legend for expansion of abbreviations.
Figure 4 –
Figure 4 –
Genotypic similarity between isolated strains from soil and water and isolates from patients. See Figure 2 legend for expansion of abbreviations.
See this image and copyright information in PMC

Comment in

  • How is TB transmitted?
    Click ES. Click ES. Chest. 2015 Apr;147(4):e158. doi: 10.1378/chest.14-3111. Chest. 2015. PMID: 25846543 Free PMC article. No abstract available.
  • Response.
    Velayati AA, Farnia P, Mirsaeidi M. Velayati AA, et al. Chest. 2015 Apr;147(4):e158-e159. doi: 10.1378/chest.14-3235. Chest. 2015. PMID: 25846544 Free PMC article. No abstract available.

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