Mutational Frequencies in Mycobacterial rpoB gene using GeneXpert/MTB Rif Assay in Rifampicin Resistant patients at a tertiary care setting in Urban Sindh, Pakistan: Analysis from a Five-Year Period

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.