Molecular epidemiology and antimicrobial resistance of group A streptococcus recovered from patients in Beijing, China

Abstract

Background: Group A streptococcus (GAS) is an important human pathogen responsible for a broad range of infections. Epidemiological surveillance has been crucial to detect changes in the geographical and temporal variation of the disease pattern. The objective of this study was to investigate the molecular epidemiological characteristics and antimicrobial resistance of GAS isolates from patients in Children's Hospital in Beijing. Methods: From 2016 to 2017, pharyngeal swab samples were collected from the outpatients in Children's Hospital, Capital Institute of Pediatrics, who were diagnosed with scarlet fever. Antimicrobial susceptibility test was performed according to the distribution of conventional antibiotics and Clinical and Laboratory Standards Institute (CLSI) recommendations. The distribution of the macrolide-resistance genes ( ermB, ermA, mefA ), emm (M protein-coding gene) typing, and superantigens (SAg) gene profiling were examined by polymerase chain reaction (PCR). Results: A total of 297 GAS strains were collected. The susceptibility of the strains to penicillin, ceftriaxone, and levofloxacin was 100%. The rate of antimicrobial resistance to erythromycin and clindamycin was 98.3% and 96.6%, respectively. The dominant emm types were Streptococcus pyogenes (Lancefield group A streptococcus; GAS) is a major pathogen causing infectious diseases in children. It causes suppurative and non-suppurative diseases, such as erysipelas, suppurative tonsillitis, scarlet fever, rheumatic fever, and glomerulonephritis [1]. Globally, there are about 616 million cases of GAS pharyngitis every year, among which, 17,800 cases are new infections, and about 517,000 patients with severe GAS are deceased every year [2]. Recently, the positive rate of GAS was estimated at 21.2% in the pharyngeal culture of patients diagnosed as "streptococcal infection/tonsillitis/angina" [3]. Moreover, the incidence of streptococcal pharyngitis is common in children aged 0-14 years. From 2012 to 2014, the average number of positive cases of streptococcal culture was 2685.1/100,000 children in Beijing, including 1652.7 outpatient visits [4]. In 2011, scarlet fever broke out in mainland China and Hong Kong, with a sharp increase in incidence [5,6]. Penicillin is the preferred clinical treatment of GAS infection, while erythromycin is the first alternative antibiotic for patients allergic to penicillin, followed by clindamycin. The drug resistance rate to macrolides, used as alternative antibiotics, is gradually increasing, which might be related to the overuse of such antibiotics [7,8]. In our previous study, 95 isolates were recovered from suppurative tonsillitis, acute glomerulonephritis, scarlet fever and streptococcal dermatitis. The resistance rates of the isolates to erythromycin, clindamycin and tetracycline were 98.9%, 100%, 94.7% respectively [9] .The M protein encoded by the emm gene is the main pathogenic factor of GAS, and different types vary in pathogenicity. Therefore, emm typing is employed to track outbreak and routinely mo...