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

Rocio Lopez-Alvarez,Addy C Helguera-Repetto,Diana Aguilar,Claudia Badillo-Lopez,Ivan Castillo-Ramirez,Sofia Samper,Rogelio Hernandez-Pando,Sandra Rivera-Gutierrez,Jorge A Gonzalez-Y-Merchand,Jorge F Cerna-Cortes

doi:10.1186/1471-2180-10-82

Abstract

BackgroundThe 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.ResultsOf 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.ConclusionsThis 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.

Highlights

The prevalence of infections with Mycobacterium tuberculosis (MTb) and nontuberculous mycobacteria (NTM) species in human immunodeficiency virus (HIV)-infected patients in Mexico is unknown
The aims of this study were to determine the prevalence of mycobacterial species in HIV-infected patients from Mexico City and surrounding areas, to evaluate the genotypic diversity of the Mycobacterium tuberculosis complex (MTC) strains using IS6110 restriction fragment length polymorphism (RFLP), spoligotyping and mycobacterial interspersed repetitive units (MIRU)-variable numbers of tandem repeats (VNTR), to determine their drug resistance profiles, and to detect mutations present in katG, inhA and RNA polymerase b-subunit (rpoB) genes that lead to the selection of INH- and RIF-resistant strains
Mycobacteria prevalence in HIV-infected patients In this study we characterized 67 mycobacterial strains isolated from HIV-infected patients, 85% of strains belonged to the MTC; 48 (71.6%) were MTb, 9 (13.4%) M. bovis, and the remaining 15% were NTM: 9 (13.4%) corresponded to M. avium and 1 (1.5%) to M. intracellulare

Summary

Introduction

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 to detect mutations present in katG, rpoB and inhA genes, resulting in isoniazid (INH) and rifampin (RIF) resistance. In Mexico, HIV-infected patients account for 1.0% of new TB cases [4]. It has been reported that in HIV-infected patients, Mycobacterium tuberculosis (MTb) is not the only mycobacteria that causes disease, nontuberculous mycobacteria (NTM) have been found in such patients [5,6]. In Mexico identification of mycobacterial species is generally based on clinical features, sometimes with the help of a positive acid-fast stain [7]

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