Clinical Microbiology: Open Access

Rifampicin and isoniazid resistance associated gene mutations and heteroresistance among Mycobacterium tuberculosis isolates: A cross sectional study design in Amhara National Regional state, Ethiopia

3^rd International Conference on Clinical Microbiology & Microbial Genomics

September 24-26, 2014 Valencia Convention Centre, Spain

Daniel Mekonnen Nigus, Aschalew Admassu Tamiru, Wondemagegn Mulu Lingerew, Fantahun Biadglegne Degeneh, Bayeh Abera Beyene, Arancha Amor Aramendia and Woynshet Gelaye Yalew

Accepted Abstracts: Clin Microbial

Abstract:

Background: The emergence of drug resistance to Mycobacterium tuberculosis (M. tuberculosis) is an increasing threat to tuberculosis (TB) control programme. Mutations in a ?hotspot? region of 81 base pairs (bp) of rpoB gene have been found in about 96% of rifampicin (RMP) resistant M. tuberculosis. Codon 531 and 526 are the most frequently reported mutations for RMP resistance in the majority of the studies. On the other hand, between 50% and 95% of isoniazid (INH) resistant strains have been found to contain mutations in codon 315 of the katG gene. This study aimed to estimate the molecular epidemiology and heteroresistance of RMP and INH resistance determining genes in M. tuberculosis isolates in Amhara National Regional State (ANRS), Ethiopia. Methods: This cross sectional study was conducted on 270 isolates collected from all zones of ANRS from May/2012 to June/2013. DNA extraction was carried out using mechanical and GenoLyse? chemical methods alternatively. The amplification, DNA addition, hybridization and interpretation were done based on GenoTypeMTBDR plus assay (HainLifescience, Nehren, Germany). Descriptive statistics was used to visualize differences within the data. Extraction positive control (H37Rv), extraction and master mix negative control (molecular grade water) were used. Results: Among 133 (49.3%) RMP resistant isolates, S531L substitution accounted 64 (48.1%). Disappearance of rpoBWT8 band without appearance of rpoB MUT3 was 8 (6.0%). H526Y and H526D substitution was found to be 12 (9%) and 7 (5.3%), respectively. The prevalence of RMP heteroresistance was 7 (5.3%). Out of 139 INH resistance gene mutations, 117 (84.2%) was due to S315T1 substitution. Moreover, 5 (3.6%) resistant isolates were associated with mutation from nucleic acid position 15 of inhAWT1 gene (C15T substitution) and 3 (2.2%) with both S315T1 & C15T substitutions. Prevalence of INH heteroresistance was 1 (0.72%). Conclusions: Large proportion RMP resistance was due to S531L and H526Y substitution. S315T1 substitution was the highest resistance determining gene mutation for INH. However, most rpoB and KatG WT gene mutations appeared without associated mutant gene, indicating additional mutant probes should be included in the kit in the future. The study also showed that RMP heteroresistance was higher than INH heteroresistance.