Screening for streptomycin resistance conferring mutations in Mycobacterium tuberculosis isolates from Iran

Point mutations in the rpsL and rrs genes can lead to development of streptomycin (STR) resistance in Mycobacterium tuberculosis. The aims of this study were to determine the frequency of mutations in STR resistant M. tuberculosis isolates in Iran and to analyze the possible relationship between bacterial genotype and STR resistance. Twenty-three M. tuberculosis samples comprising 9 multidrug-resistant (MDR) and 14 non-MDR isolates, recovered from TB patients in four regions: Tehran (n = 14), Isfahan (n = 2), Zahedan (n = 2), and Khorasan (n = 5), were analysed. Mutational profiling was performed by sequencing of the rrs and rpsL genes and spoligotyping method was used for genotyping. Nineteen isolates were resistant to STR, among them 7 exhibited mutations in the rpsL gene and 7 had mutations in the rrs gene. The remaining 5 STR resistant as well as all susceptible isolates lacked any mutation in both genes. Beijing genotype was associated with both MDR and STR resistance in which all mutations occurred at codon 43 of the rpsL gene. There was an association between mutations in the rpsL and rrs genes and STR resistance. We also found a correlation between Beijing genotype and STR resistance.