Epidemiology and antibiotic resistance of group A streptococci isolated from health schoolchildren in Korea

Objectives: To assess the epidemiology, antibiotic resistance and genotypic characterization of group A streptococci (GAS) in Jinju, Korea. Methods: Isolates were characterized in terms of their antibiotic resistance, the phenotypes of erythromycin resistance, the frequencies of erm(B), erm(A) and mef(A) genes, and by emm genotyping or M typing. The data were compared with those from 85 GAS strains collected during 1995 in the same area. Results: A total of 98 (16.9%) of 581 healthy schoolchildren yielded GAS from throat swab culture during 2002. The most frequent emm types were emm12 (34.4%), followed by emm75 (10.4%), emm18 (9.4%), emm22 (8.3%) and emm1 (7.3%) in 2002, whereas M12 (21.2%) and M22 (14.1%) were common in 1995. The resistance rates to erythromycin and clindamycin in 2002 were 51.0% and 33.7%, respectively, compared with 29.4% and 10.1% in 1995. Among the erythromycin-resistant strains, constitutive resistance, inducible resistance, and the M phenotype were observed in 61.2%, 2.0% and 36.7% in 2002, compared with 64.0%, 0% and 36.0% in 1995, respectively, which correlated with the presence of resistance genes. Most of the emm12 strains showed constitutive resistance, whereas emm18 and emm75 showed the M phenotype. The organisms with other emm genotypes were susceptible to both erythromycin and clindamycin. Conclusions: Erythromycin and clindamycin resistance increased markedly during the period 1995-2002 in Korea. Constitutive resistance is more common than the M phenotype, with inducible resistance occurring rarely. The phenotypes of erythromycin resistance seem to be associated with certain emm genotypes.