emm Types and Clusters of Group A Streptococcus Causing Acute Pharyngitis in Changwon Korea, 2018–2019

Background: Group A streptococcus (GAS) is the most common cause of bacterial pharyngitis. This study aimed to characterize the molecular epidemiology of GAS infection using an emmtyping and emm-clustering approach. Methods: A total of 372 patients from Changwon who showed pharyngitis symptoms were recruited during the sampling period of 2018–2019 and throat cultures were obtained from them. emm typing was performed using polymerase chain reaction (PCR) and direct sequencing. emm genotypes and GAS clusters were classified based on a web-based database. Results: Of the 372 throat swab specimens, 101 (27.2%) were positive for GAS. emm typing analysis was performed on 59 GAS isolates. The most prevalent emm type was emm89 (20.3%), followed by emm12 (16.9%). Seven emm clusters were identified: E4 (emm89/ emm28, 32.2%), A-C4 (emm12, 16.9%), E1 (emm4, 13.6%), A-C5 (emm3, 10.2%), E6 (emm75, 8.5%), M6 (emm6, 8.5%), and A-C3 (emm1, 6.8%). Conclusion: Diverse and temporal changes were observed in the distribution of emm types and clusters of GAS. Continuous surveillance based on emm genotyping is needed to monitor the epidemiological characteristics of GAS pharyngitis.