Abstract
Objectives:To assess the mutational frequencies in Mycobacterial rpoB gene using GeneXpert/MTB Rif Assay in rifampicin resistant patients during 2013-2017 at a tertiary care setting in Urban Sindh, Pakistan.Methods:This Retrospective Descriptive Cross-Sectional Study was conducted at the TB laboratories, Ojha Institute of Chest Diseases, Dow University of Health Sciences. The record of 713 positive cases of Rifampicin Resistant Tuberculosis from January 2013 to December 2017 were analysed. These were diagnosed using GeneXpert® that detects mutations in the 81 base pair region of rpoB gene with the help of five molecular probes A, B, C, D and E. All invalid and extra pulmonary samples were excluded.Results:In total, 713 cases were found to be rifampicin resistant during the five-year period, among which 374 (52.45%) were males while 339 (47.55%) were females. Among the five standard probes A, B, C, D and E, 97.48% of the cases had a single mutation. Among these, mutations in Probe E (66.48%) were the most common, followed by Probe B (14.3%) and Probe D (11.08%). Only 13 cases (1.82%) of double mutations and five cases (0.7%) of triple mutations were detected.Conclusion:The rpoB gene Probe E region 529-533 appears the most potent site for a mutation and development of rifampicin resistance in the rpoB gene in Mycobacterium tuberculosis, that encodes the β-subunit of RNA polymerase. The most affected age-group in both males and females is 19-45 Years.
Highlights
Drug Resistant Tuberculosis (DR-TB) is a worldwide health problem
This study aims to determine the relative frequencies of different regional mutations through assessing the relative frequencies of associated probes for various rpoB gene mutations by GeneXpert MTB/RIF Assay
Gender-wise data were tabulated (Table-II) in relation to different probes from the 363 male and 332 female patients, who were resistant to rifampicin patients and the region examined by Probe E was found to be the most commonly affected by the mutation, followed by that of Probe B
Summary
Drug Resistant Tuberculosis (DR-TB) is a worldwide health problem. it is difficult to treat and the cost of treatment of DR-TB is much higher than the ordinary disease. Pak J Med Sci July - August 2021 Vol 37 No 4 www.pjms.org.pk 1151 by detecting mutations in the rpoB gene It uses a Real time PCR based closed system and detects changes in rpoB gene that encodes β subunit of RNA polymerase, the site where rifampicin binds and inhibits the polymerase from transcribing and stopping the protein production. It uses five different overlapping probes A, B, C, D and E to detect mutations in codons from 507-511, 511518, 518-523, 523-529 and 529-533, respectively.[3] These probes assist in differentiating among the wild type and mutated forms that are associated with rifampicin resistance. Different types of mutations have different effects on the bacterial physiology and survival, knowing the types, frequencies and geographical correlates of these mutations may influence future interventions
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