Distribution of emm types among Group A Streptococcus isolates from children

Abstract

Background: Group A streptococcus (GAS) is a common human pathogen responsible for a wide spectrum of diseases. The variation in the predominant emm type is known to able to affect the incidence and clinical manifestations of GAS infections. Recently, increase of invasive GAS infections and several outbreaks of scarlet fever have been reported in several countries. We investigated the clinical characteristics and molecular epidemiology of GAS infection in Korea. Method: GAS strains previously obtained from clinical isolates at the Seoul National University Childrens Hospital between 1991 and 2012 and the Seoul National University Bundang Hospital between 2006 and 2012 were analyzed. The clinical characteristics were reviewed by medical records and antimicrobial resistance was investigated by disk diffusion test and E-test. The emm genotypes and pyrogenic exotoxin genes (speA, speB, speC) were identified using polymerase chain reaction (PCR) and sequencing. Results: A total of 155 GAS cases were investigated. Among these cases, the clinical diagnosis was as followed: pharyngitis 44 (28.4%), scarlet fever 41 (26.5%), noninvasive skin and soft tissue infection (SSTI) 37 (23.9%), invasive disease 19 (12.3%), poststreptococcal glomerulonephritis (PSGN) 4 (2.6%), rheumatic fever 2 (1.3%), and others 8 (5.2%). All GAS isolates were sensitive to penicillin. The erythromycin resistance rate was 10.3% (16/155), and all isolates during the recent 3 years were susceptible to erythromycin. The most prevalent emm types were emm1 (19.4%), emm12 (18.7%) and emm4 (18.1%). Distribution of emm genotype differed according to clinical disease. The emm1 was most common (47.4%) in invasive GAS infections and emm4 was most common (48.8%) in scarlet fever. The emm12 was the most common type in pharyngitis (25.0%) and SSTI (29.7%). During the recent 3 years, there was an increase in invasive GAS infections and scarlet fever which was correlated with an increase in specific emm types, emm1 and emm4, respectively. According to the analysis of exotoxin genes, speB was found in all isolates and speA and speC genes were detected in 36.8% and 49.0% of the isolates, respectively. The speC detection rate was high (65.9%) in scarlet fever compared to other GAS infections (P=0.017). Conclusion: There has been a recent increase in invasive GAS infections and scarlet fever associated with an increase of emm1 and emm4, respectively. Changes in prevalent GAS genotypes and diversity in disease emphasizes the importance of continuous surveillance on clinical and molecular characteristics of GAS.