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

Abstract

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 emmtypingand emm-clustering approach. Methods: A total of 372 patients from Changwon who showed pharyngitis symptoms wererecruited during the sampling period of 2018–2019 and throat cultures were obtainedfrom them. emm typing was performed using polymerase chain reaction (PCR) and directsequencing. emm genotypes and GAS clusters were classified based on a web-baseddatabase. Results: Of the 372 throat swab specimens, 101 (27.2%) were positive for GAS. emm typinganalysis was performed on 59 GAS isolates. The most prevalent emm type was emm 89(20.3%), followed by emm 12 (16.9%). Seven emm clusters were identified: E4 (emm 89/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 typesand clusters of GAS. Continuous surveillance based on emm genotyping is needed to monitorthe epidemiological characteristics of GAS pharyngitis.