Decrease of erythromycin resistance in group A streptococci by change of emm distribution.

With the increasing resistance of group A streptococci (GAS) to macrolides in some countries including Korea, throat cultures were taken from healthy elementary school children to isolate GAS in 2004. Antibiotic susceptibility, macrolide-resistant phenotypes and genotypes as well as emm genotyping were studied and compared with previous data in 2002. In the present study, resistance rates to erythromycin and clindamycin in 2004 decreased to 9.8 and 8.8%, respectively, compared with 51.0 and 33.7%, respectively, in 2002. While emm44/61 increased from 0 to 29.3%, emm12 decreased from 34.4 to 6.4% during the 2002 - 2004 period. All emm44/61 strains were susceptible to erythromycin, while 81.0% of emm12 strains were resistant to erythromycin. The dramatic decrease of erythromycin resistance during this short period might be related to a change in the distribution of emm types in the community.