Molecular analysis of streptomycin-resistance associating genes in Mycobacterium tuberculosis isolates from Nepal

Mutation in rpsL (encoding ribosomal protein S12), rrs (encoding 16S ribosomal RNA) and gidB (encoding 7-methylguanosine methyltransferase) are associated with resistance to streptomycin (STR), which is used for the treatment of multi-drug resistant tuberculosis (MDR-TB) in Nepal. The aim of our study is to analyze the correlation between mutations in the target genes and STR-resistance in 197 Mycobacterium tuberculosis (MTB) isolates from Nepal. Mutations in rpsL was harbored by 65.9% of isolates, in which the most common mutation in rpsL is caused by K43R (58.8%) and were significantly associated with Beijing genotype (P < 0.001). About 13.2% of isolates harbored mutations in two highly mutable regions of rrs, the 530 loop and the 912 region. About 13.2% of gidB mutants do not show any mutation in rpsL and rrs, which might suggest the role of gidB mutations in STR-resistance in MTB. In addition, 5.6% of isolates do not show any mutations in three genes examined, suggesting the involvement of other mechanism in STR-resistance in MTB. Our findings can be implemented for the establishment of molecular STR-susceptibility testing, in which tuberculosis can be treated with appropriate drugs and can improve control strategies for DR-TB.