Identification of mutations in rpoB gene (ß-sub unit of DNA dependent RNA polymerase) in rifampicin resistant mycobacterium tuberculosis among retreatment tuberculosis patients in nepal

Abstract

Identification of mutations in rpob gene (ß-sub unit of dna dependent rna polymerase) in rifampicin resistant mycobacterium tuberculosis among retreatment tuberculosis patients in nepal streptomycin, isoniazid, rifampicin, ethambutol). There was no significant difference of age wise (p=0.532) and sex wise (p=0.775) distribution of MDR-TB cases identified by Gene Xpert, conventional culture and FLD-DST. Second line antituberculosis

drug susceptibility test (SLD-DST) on 29(26.6%) of 109 MDR confirmed M. tuberculosis isolates was performed by Line Probe Assay (LiPA Genotype MTB/DRsl version 1.0), of which 17(58.6%) for gyrA and 8(27.6%) for emb B and all 29(100%) for rrs genes were identified as wild type. Whereas, 12(41.4%) were resistant to gyr A gene i.e. 3 cases resistant to fluoroquinolone alone and 9 cases along with ethambutol. Similarly, 10(34.5%) were resistant to ethambutol (emb B genes) only and 7(24.1%) were susceptible to all SLDs. Out of 29 MDR confirmed M. tuberculosis isolates, 12(41.4%) were found to be pre-extensively drug resistant (pre-XDR-TB) but none was found XDR TB. The maximum number of age/sex wise pre-XDR TB distribution was found in 15-60 years of age group and among females and males equally. There were no differences of age (p=0.531) and sex wise (p=0.428) findings of pre-XDR TB. Among 159 RR/MDR-TB, 128(80.5%) cases were analyzed for time difference between previous cure, current diagnosis of MDR-TB and treatment outcome. The treatment outcomes were categorized into favorable (cured and treatment completed) and unfavorable (died, lost to follow up, not evaluated and treatment failure) groups. The age wise treatment outcomes for a total of 128(100.0%) cases; 1(1.1%), 80(62.5%), 8(9.0%) were among the favorable group and 1(2.6%), 34(26.6%), 4(10.3%) were among unfavorable groups of <15, 1560 and > 60 years of age respectively. Similarly, 2(1.6%) i.e. 1(0.8%) in 5-11 months

and 1(0.8%) in 1-4 years groups were not evaluated, 3(2.3%)

i.e. 1(0.8% fell in 1-4 years and 2(1.6% fell in ≥5yrs) groups respectively were treatment failure. There were no significant differences of age (p=0.897), sex (p=0.357), time difference (p=0.474), diagnosis by Gene Xpert alone or along with C/DST (p=0.746) and treatment outcomes. This is the first analyzed report on retreatment TB patients in Nepal.