LAUSR

OBJECTIVES The number of multidrug-resistant tuberculosis (MDR-TB) cases is rising worldwide. The present investigation aimed to evaluate, using the GenoType® MTBDRplus assay, the most common mutations associated with rifampicin (RIF) and isoniazid (INH) resistance among resistant strains in Morocco. METHODS A total of 319 Mycobacterium tuberculosis isolates sent to the National Tuberculosis Reference Laboratory between 2013 and 2015 were subjected to GenoType® MTBDRplus for detecting M. tuberculosis and determination of drug susceptibility. Correlation of the minimum inhibitory concentrations (MICs) of INH with genotypic assay results was carried out for 97 MDR-TB strains. Various concentrations of INH were tested. RESULTS The most frequent mutations observed were rpoBS531L (67.2%) and katGS315T1/2 (66.5%). Isolates with inhA gene mutation, katG gene mutation, and dual mutations in katG and inhA had MICs ranging from 0.5-1μg/mL, 2-10μg/mL and ≥12μg/mL, respectively. CONCLUSION In Morocco, 66.5% and 76.7% of M. tuberculosis strains carried mutations causing high-level resistance to INH and RIF, respectively.