Abstract
The relationship between streptomycin (SM) susceptibility and rpsL mutations of Mycobacterium tuberculosis strains was studied. Of 18 clinically isolated SM-resistant. M. tuberculosis strains, mutation was suspected in 9 strains (50%) with SM MICs of≥256μg/ml by PCR-single strand conformation polymorphism targeting rpsL gene. On the other hand, using PCR-direct sequence method, amino acid substitution caused by single nucleotide point mutation in rpsL gene was demonstrated in 11 out of 18 strains (61%). The same amino acid substitution at codon 43 (Lys→Arg) was observed in all 11 strains with SM MICs of≥256μg/ml. In addition, PCR products obtained from these 11 strains could not be cut by a restriction enzyme, Mbo II, while H137Rv strain and the other 32 strains with SM MICsof<256μg/ml were cutinto 2 fragments. In conclusion, ourresults suggest that highly SM-resistant M. tuberculosis strains with MICs of≥256μg/ml could be rapidly and easily detected by the restriction enzymatic method.
