Genetic diversity among Mycobacterium tuberculosis isolates from Mexican patients

Forty-six isolates of the Mycobacterium tuberculosis complex were typified by PCR of the IS6110 region and by Mycobacterium bovis specific primers JB21/JB22. Isolate MVG01 was typified as M. bovis, being the first record of a case of human tuberculosis caused by this species in Mexico. RAPD-PCR was used to describe the genetic diversity of the remaining 45 M. tuberculosis complex isolates. The corrected genotypic diversity value calculated for the analyzed population was 0.96, the estimated mean gene diversity was 0.235, and the corrected Shannon-Weiner index was 2.15. All allele-loci combinations generated showed significant linkage disequilibria. The distribution of genetic variation was analyzed both by the unweighted pair group method with arithmetic averages clustering and by principal coordinates analysis. Unweighted pair group method with arithmetic averages clustering resulted in a tree with four main clusters and one unclustered strain (MVG20), the principal coordinates analysis strain distribution pattern being consistent with this grouping. The obtained results suggest that the studied isolates belong to a clonal population having significant genetic diversity. Our genetic diversity results are comparable with those reported for other populations of M. tuberculosis, although only three RAPD primers were used.