Objectives: To assess the epidemiology, antibiotic resistance and genotypic characterization of group A streptococci (GAS) in Rawalpindi, Pakistan.
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.
Results: A total of 198 (30 %) of 650 healthy school children yielded GAS from throat swab culture during 2016. The most frequent emm types were emm12 (38.3%), followed by emm75 (13.2%), emm18 (10.4%), emm22 (9.3%), emm1 (8.3%). The resistance rates to erythromycin and clindamycin were 61.0% and 47.7%, respectively. Among the erythromycin-resistant strains, constitutive resistance, inducible resistance, and the M phenotype were observed in 61.2%, 2.0% and 36.7%, 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 is quite high in Rawalpindi, Pakistan. Constitutive resistance is more common than the M phenotype, with inducible resistance occurring rarely.