Relationship between genetic alteration of the rpsL gene and streptomycin susceptibility of Mycobacterium tuberculosis in Japan

We have investigated the effect of genetic alterations in the rpsL gene on the MICs of streptomycin for Mycobacterium tuberculosis strains. Direct DMA sequencing showed a point mutation in 23/121 strains; in 18 strains the mu tation was associated with an amino acid change. The MICs of streptomycin i n 22 out of 23 point-mutated strains were greater than or equal to 256 mg/L . Restriction fragment length polymorphism (RFLP) analysis showed mutations at codon 43 in all 18 strains with point mutations in the same codon. Our results suggest that both RFLP and base sequencing analysis of the rpsL gen e are useful for the rapid prediction of highly streptomycin-resistant stra ins of M. tuberculosis.