Mingliang Chen, Jiehao Cai, Mark R Davies, Yuefang Li, ChiZhang, Weilei Yao, Dechuan Kong, Hao Pan, Xi Zhang, Min Chen and Mei Zeng
Shanghai Municipal Center for Disease Control and Prevention, China Children's Hospital of Fudan University, China The Peter Doherty Institute for Infection and Immunity-University of Melbourne, Australia Shanghai Institutes of Preventive Medicine, China
Posters & Accepted Abstracts: J Infec Dis Treat
Since 2011, epidemics of scarlet fever have resurged in several countries, including China, where emm12 group A Streptococcus (GAS) was responsible for the 2011 large outbreaks. Afterwards, scarlet fever outbreak occurred annually. To date, factors driving the outbreaks have not been well elucidated. Epidemiological data of scarlet fever in Shanghai during 2011-2015 were obtained from the National Notifiable Infectious Disease Surveillance System. Throat swabs of patients with scarlet fever from the Sentinel Hospital, from which 50% of scarlet fever cases in Shanghai were reported, were cultured. GAS carriage surveillance was performed in schools located in three districts. A total of 1,568 GAS isolates were collected for analysis, including 1,451 isolates from patients and 117 from carriers. This continuous study showed that the annual incidence of culture-confirmed scarlet fever was 7.5-19.4/100,000-person-year in Shanghai during 2011-2015, with an average GAS carriage rate being 7.6% in school-aged children. Twelve emm types were identified with co-predominance of emm12 (61.8%) and emm1 (35.9%), which harboured different super-antigen profiles. The proportion of emm1 GAS strains increased from 3.8% in 2011 to 48.6% in 2014. Two predominant clones identified by pulsed-field gel electrophoresis, SH001-emm12 and SH002-emm1, were discovered in 66.9% of scarlet fever cases and 50% of carriers, respectively. The frequencies of resistance to macrolides and tetracycline among GAS isolates were both over 95%, which was mediated by ermB and tetM, respectively. GAS population is changing, and ongoing surveillance is warranted to monitor the dynamic changes of GAS emm type, predominant clone, and superantigen profile.