Molecular Epidemiology of Rifampicin Resistance in Mycobacterium tuberculosis Using the GeneXpert MTB/RIF Assay from a Rural Setting in India.

Raghuprakash Reddy,Gerardo Alvarez-Uria

doi:10.1155/2017/6738095

Abstract

The Xpert MTB/RIF assay can detect mutations in rpoB gene that confer rifampicin resistance (RR) using five overlapping probes (A, B, C, D, and E). In this study, we described our experience with the Xpert assay in a rural setting in India. During the study period, 3250 samples were processed. The result was unsuccessful in 5.7% of cases. For extrapulmonary specimens, the risk of unsuccessful result was higher in tissue biopsy and stool samples. Among samples positive for Mycobacterium tuberculosis, rifampicin resistance was indeterminate in 1.2% of them. Our results and a review of the literature showed that the most frequent mutations conferring RR were located in the region of Probe E (63.6%; 95% confidence interval [CI] 56.26–70.94), followed by Probe B (15.02%; 95% CI 11.94–18.10), Probe D (13.35%; 95% CI 10.01–16.69), Probe A (4.73%; 95% CI 1.92–7.54), and Probe C (1.61%; 95% CI 0.67–2.54). Although the high cost of the cartridges precluded using the Xpert assay for routine diagnosis of tuberculosis, our results demonstrate that the assay can be used to diagnose RR-tuberculosis in rural areas with limited laboratory infrastructure and could be a convenient tool to investigate the molecular epidemiology of RR in resource-limited settings.

Highlights

Rifampicin is arguably the most important drug in the treatment of tuberculosis (TB)
The probe that confers rifampicin resistance (RR) is rarely reported in the clinical practice, the frequency of specific mutations in the rpoB region could provide useful information when studying the epidemiology of RR-TB in a particular region
We describe our experience with the GeneXpert MTB/RIF assay and the molecular epidemiology of RRTB in a rural setting in South India

Summary

Introduction

Rifampicin is arguably the most important drug in the treatment of tuberculosis (TB). Infection by rifampicin resistance (RR) TB requires long therapy with less effective and more toxic second-line drugs [1]. Diagnosis of RR-TB has been traditionally difficult, because it required sophisticated biosafety and laboratory infrastructures, which could be available in urban areas but hardly in rural settings. The assay requires minimal technical expertise and basic biosafety measures. The Xpert assay can detect mutations in five regions of the beta-subunit of the RNA polymerase enzyme (rpoB) gene using five overlapping probes (A, B, C, D, and E) [3]. The probe that confers RR is rarely reported in the clinical practice, the frequency of specific mutations in the rpoB region could provide useful information when studying the epidemiology of RR-TB in a particular region

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Discussion

Conclusion