The prevalence of emm types and Resistance to Erythromycin Pattern among group A Streptococci

Background and objectives: Group A Streptococcus (GAS) strains havebeen identified by serologic methods based on surface protein antigens, Tand M. Accordingly, different serotypes have been reported worldwide.Recently, the previous out of date procedures have been replaced by Nterminalemm gene sequence, which has been used in identifying more than150 emm types. We aimed to determine the prevalence of emm types andphenotypes resistance to erythromycin among streptococci isolated fromthe throat in north of Iran.Material and Methods: 50 GAS isolates from sore throat of patientsreferred to a few local hospitals in Tonekabon, Ramsar, and Chalus innorthwest of Iran (2010-2011), by using blood agar, bacitracin sensitivitytest, PYR test and agglutination by specific antiserum. Antibiotic resistanceof the isolates was determined by the discs branded by Iranian Padtan TebCompany, using Kirby Bauer Test, and analyzed by CLSI standards. Themechanism of resistance to erythromycin was evaluated by Double DiskDiffusion Test in the presence of erythromycin and clindamycin. emmgene of all isolates were reproduced and their PCR products sequenced bythe Korean Macrogen company. To determine the emm types, usingBLAST2.0 program (National Center for Biotechnology Information,available in WWW.ncbi.nlm.nih.gov / BLAST), and the emm genesequences were compared with sequences in the gene bank.Results: we identified Four different types of emm, including e mm5 (26;52 %), emm12 (12; 24%), emm79 (6; % 12) and emm86 (6; % 12). All betalactam antibiotics have inhibitory effect on isolates, while18% of isolates (9of 50) are resistant to erythromycin. The most common resistancephenotype is cMLSB (% 66.6) and the next one is phenotype M (% 33.3),but phenotype iMLSB is not observed in none of the isolates. Twelvepercent (6cases) of isolates are resistant to clindamycin.Conclusion: The results of present study show different types of GAS thanthose reported worldwide. The emergences of emm86 in pharyngitis anderythromycin resistance are the two valuable findings of this research.Keywords:Streotococcus pyogenes,erythromycin,cMLSB,iMLSB