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, BT3 and BT4,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, 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. Conclusion: In addition to mutation at the position 2058 other point mutations in different positions of domain V involve in the resistance to macrolides.