Characterization of Hypervariable Region of Gyra And Gyrb Genes of Mycobacterium Tuberculosis from Jeddah, KSA

Abstract

Mycobacterium tuberculosis (MTB) is an old enemy of the human race, with evidence of infection observed as early as 5000 years ago.MTB infection is relatively high in Jeddah as compared to other cities of Saudi Arabia due to high influx of people from across the globe for pilgrimage. This study aimed to investigate the phenotypic drug resistance for the first line antituberculous drugs and to explore mutations in fluoroquinolone resistance gyrA and gyrB genes in  Mycobacterium tuberculosis (MTB) isolates from  tuberculosis patients from Jeddah, Saudi Arabia during 2015. Firstly, phenotypic drug susceptibility tests (DST) were performed for first line antituberculous drugs for all the MTB isolates. DST for rifampicin, isoniazid,streptomycin, ethambutol, and pyrazinamide were performed. Then the hypervariable regions of gyrA and gyrB genes were sequenced to identify mutations for Fluoroquinolones (FQs) resistance . Overall, all the MTB isolates were susceptible to Sterpt, RIF and Eth. Where as resistance to INH and Pyr were 2% and 14% respectively. Genotypic resistance revealed mutations in gyrA and gyrB genes among 96% (48/50) of FQ resistant isolates. 96% (48/50) of FQ resistant isolates showed mutations at codons 95 (S95T)  and three pattern of double mutations in gyrA gene ; six with E21Q & S95T, and the two with I29S & S95T, and one with A90V & S95T. The mutation in gyrB gene was identified in two of 50 clinical isolates in this study . K421R and T420. For clinical isolates, gyrB mutations appear to be of much rarer occurrence.We conclude that occurrence of mutations at only four codons in gyrA and two codon in  gyrB genes among FQ resistant isolates may assist in development of rapid molecular method for FQ resistance detection. Presence of mutations among more than fifty percent of intermediate susceptible FQ MTB isolates could also serve as a predictor for pre-resistant isolates.