Analysis of rpsL and rrs genes mutations related to streptomycin resistance in Mdr and Xdr clinical isolates of Mycobacterium tuberculosis.

INTRODUCTION:Streptomycin is a bactericidal and aminoglycoside antibiotic. It is one of the most effective drugs for treatment of multi-drug Tuberculosis disease. Incidence of resistance is increasingly reported. Its action mechanism is by inhibition of binding aminoacyl tRNA to position "A" in elongation phase, which finally it causes to stop bacterial protein synthesis. In this study, resistance rapid investigation to streptomycin was conducted in clinical strains of Mycobacterium tuberculosis. MATERIALS AND METHODS:In this study, among 105 strains of phlegm-positive and culture-positive Mycobacterium tuberculosis, 45 strains of resistant and sensitive to streptomycin were selected for possible mutations examination in genes rrs and rpsL. Specific primers that used for PCR were named rpsL 1, rpsL 2 and rrsR, Frrs. PCR products were sequenced. RESULT:PCR Products represents 504 bp band for gene rpsL and 1027 bp for gene rrs that shows proper selection of primers and determining an amplification appropriate program. From 26 resistant strains to streptomycin 26 strain have mutation in rpsL gene and 1 strain have alteration in rrs gene. In this study 19 strains were sensitive to streptomycin that have no mutation in these gene. CONCLUSIONS:Streptomycin resistance is mainly related to mutation at codons 43 and 88 "rpsL" gene and to a lesser extent "rrs" that are the greatest cause of drug resistance to streptomycin.

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