detection of mutation in 23s rrna in isolates of streptococcus pyogenes resistant to erythromycin

background: in this study, erythromycin resistance isolates from the students with aged 12-15 yr old were studied and the mutations in the 23s rrna were identified by sequencing. methods: throat samples of 327 students with 12-15 years old from 3 schools of tehran were cultured on the selective strep­tococ­cus pyogenes medium and 23 strains were primarily selected as s. pyogenes . results: all strains were susceptible to penicillin and bacitracin (0.04u). minimum inhibitory of concentrations (mics) for eryth­romycin were determined in which 5 strains were found intermediate, 2 strains resistance and the remaining 16 strains susceptible to erythromycin. mic for the erythromycin-resistance strains, bt 3 and bt 4 , were 8.2 and 12.4 µg/ml, respec­tively. pcr was performed for each six 23s rrna operons and a fragment with 550 bp was sequenced. for two resis­tance strains, bt 3 and bt 4 there were a mutation in position 2059 (a to g). also another mutation in position 2529 (g to a) was detected in bt3. conclusion: in addition to mutation at the position 2058 other point mutations in different positions of domain v involve in the resistance to macrolides.