Characterization ofemmtypes and superantigens ofStreptococcus pyogenesisolates from children during two sampling periods

Abstract

SUMMARY: The characteristics of 359 group A streptococcal (GAS) isolates collected from Chinese paediatric patients in two periods (1993–1994, 2005–2006) were studied. Isolates were assigned toemmtypes and assayed for eight superantigen (SAg) genes (speA,speC,speH,speI,speG,speJ,ssa,SMEZ). Typesemm1 andemm12 were consistently the most prevalent during the two periods, while others varied in frequency. GAS isolates carrying six or more SAg genes increased from 46·53% (1993–1994) to 78·39% (2005–2006);ssa,speHandspeJgenes (PspeAdeclined (Pemmtype, but strains of the sameemmtype sometimes carried different SAg genes in the two periods. No significant difference inemm-type distribution and SAg gene profile was noted between isolates from different diseases. These data may contribute towards the development of a GAS vaccine in China.