Detection of Mutation in 23S rRNA in Isolates of Streptococcus pyogenes Resistant to Erythromycin

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. Throat samples of 327 students with 12-15 years old from 3 schools of Tehran were cultured on the selective Strep tococ cus pyogenes medium and 23 strains were primarily selected as S. pyogenes. All strains were susceptible to penicillin and bacitracin (0.04U). Minimum inhibitory of concentrations (MICs) for eryth romycin 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, BT3 and BT4, were 8.2 and 12.4 µg/ml, respec tively. PCR was performed for each six 23S rRNA operons and a fragment with 550 bp was sequenced. For two resis tance strains, BT3 and BT4 there were a mutation in position 2059 (A to G). Also another mutation in position 2529 (G to A) was detected in BT3. In addition to mutation at the position 2058 other point mutations in different positions of domain V involve in the resistance to macrolides.