First insights into the genetic diversity of Mycobacterium tuberculosis isolates from HIV-infected Mexican patients and mutations causing multidrug resistance

Abstract

Background: The prevalence of infections with Mycobacterium tuberculosis (MTb) and nontuberculous mycobacteria (NTM) species in HIV-infected patients in Mexico is unknown. The aims of this study were to determine the frequency of MTb and NTM species in HIV-infected patients from Mexico City, to evaluate the genotypic diversity of the Mycobacterium tuberculosis complex strains, to determine their drug resistance profiles by colorimetric microplate Alamar Blue assay (MABA), and finally, to detect mutations present in katG, rpoB and inhA genes, resulting in isoniazid (INH) and rifampin (RIF) resistance.

Results: Of the 67 mycobacterial strains isolated, 48 were identified as MTb, 9 as M. bovis, 9 as M. avium and 1 as M. intracellulare. IS6110-RFLP of 48 MTb strains showed 27 profiles. Spoligotyping of the 48 MTb strains yielded 21 patterns, and 9 M. bovis strains produced 7 patterns. Eleven new spoligotypes patterns were found. A total of 40 patterns were produced from the 48 MTb strains when MIRU-VNTR was performed. Nineteen (39.6%) MTb strains were resistant to one or more drugs. One (2.1%) multidrug-resistant (MDR) strain was identified. A novel mutation was identified in a RIF-resistant strain, GAG --> TCG (Glu --> Ser) at codon 469 of rpoB gene.

Conclusions: This is the first molecular analysis of mycobacteria isolated from HIV-infected patients in Mexico, which describe the prevalence of different mycobacterial species in this population. A high genetic diversity of MTb strains was identified. New spoligotypes and MIRU-VNTR patterns as well as a novel mutation associated to RIF-resistance were found. This information will facilitate the tracking of different mycobacterial species in HIV-infected individuals, and monitoring the spread of these microorganisms, leading to more appropriate measures for tuberculosis control.

Figure 1

Spoligotyping, IS6110 RFLP and MIRU-VNTR patterns of M. tuberculosis (MTb) and M. bovis strains isolated from HIV-infected patients. The dendrogram is based on spoligotyping patterns. A) Spoligotyping patterns (binary representation); B) Shared-type (ST) number; C) IS6110-RFLP patterns; D) RFLP cluster; E)12 MIRU-VNTR patterns; F) Strain code. ?, new patterns of spoligotypes; ?^a, Spoligotype octal 777577777720771, ?^b, Spoligotype octal 777743677760771, ?^c, Spoligotype octal 777747677760771, ?^d, Spoligotype octal 777777705720771, ?^e, Spoligotype octal 777777705720661, ?^f, Spoligotype octal 677767604760621, ?^g, Spoligotype octal 677777477413661, ?^h, Spoligotype octal 777777660000131, ?ⁱ, Spoligotype octal 264063776776600, ?^j, Spoligotype octal 677767777777600, ?^k, Spoligotype octal 775346770000000; ●, M. tuberculosis strains with zero-copy-numbers of IS6110; H37Rv, M. tuberculosis H37Rv; BGC, M. bovis BCG; ♦, M. bovis strains. *, Reference strains used as controls. ■, INH-resistant MTb strains