Increased prevalence of group A streptococcus isolates in streptococcal toxic shock syndrome cases in Japan from 2010 to 2012

Abstract

SUMMARYStreptococcal toxic shock syndrome (STSS) is a severe invasive infection characterized by the sudden onset of shock, multi-organ failure, and high mortality. In Japan, appropriate notification measures based on the Infectious Disease Control law are mandatory for cases of STSS caused byβ-haemolytic streptococcus. STSS is mainly caused by group A streptococcus (GAS). Although an average of 60–70 cases of GAS-induced STSS are reported annually, 143 cases were recorded in 2011. To determine the reason behind this marked increase, we characterized theemmgenotype of 249 GAS isolates from STSS patients in Japan from 2010 to 2012 and performed antimicrobial susceptibility testing. The predominant genotype was found to beemm1, followed byemm89,emm12,emm28,emm3, andemm90. These six genotypes constituted more than 90% of the STSS isolates. The number ofemm1,emm89,emm12, andemm28isolates increased concomitantly with the increase in the total number of STSS cases. In particular, the number ofmefA-positiveemm1isolates has escalated since 2011. Thus, the increase in the incidence of STSS can be attributed to an increase in the number of cases associated with specific genotypes.