rpoB, katG and inhA Genes: The Mutations Associated with Resistance to Rifampicin and Isoniazid in Egyptian Mycobacterium tuberculosis Clinical Isolates

In response to the huge number of people who die yearly due tuberculosis and the emergence of multidrug resistant (MDR) M. tuberculosis, accurate and rapid detection of this resistance can improve the situation. Relapsed patients in the current work represented significant percentages among rifampicin and isoniazid resistant isolates compared to other risk factors. Two molecular techniques (Genotype MTBDRplus assay and specific gene sequencing were used to detect associated mutations in TB drug resistant isolates. The genotypic profile of Multi-drug resistant (MDR) isolates showed missing of katG wild type 1 (WT1) band. Eighty percent of isoniazid mono-resistant isolates, showed katG MUT1, 20% showed katG MUT1 and inhA MUT1, 20% showed only inhA MUT1. The molecular techniques partly predicted the level of antibiotic resistance associated with katG and/or inhA gene mutations (for isoniazid) and rpoB gene mutation (for rifampicin). MTBDRplus could clearly detect rifampicin resistance among 66.7% of MDR isolates that showed mutation band rpoB MUT3 while 33.3% of them were considered as unknown, while 100% of mono-isoniazid resistant strains were detected. A mono-resistant rifampicin isolate did not show rifampicin mutation bands by Genotype MTBDRplus assay, but it showed unexpected mutation in codon 531 of rpoB by DNA sequence analysis, it can be considered as heteroresistant strain. Gene sequencing could detect resistance associated mutations mainly in codon 315 (katG gene), position -15 (inhA gene) for isoniazid resistance and codon 531 (rpoB gene) for rifampicin resistance.