Reemergence of emm 1 and a Changed Superantigen Profile for Group A Streptococci Causing Invasive Infections: Results from a Nationwide Study

Abstract

ABSTRACT Between 1999 and 2002, 496 invasive group A streptococcal (GAS) isolates from clinical microbiological departments in Denmark and subsequently 487 (98%) questionnaires from the clinicians treating the patients were received as part of a national surveillance. emm types and streptococcal superantigen (SAg) genes were determined. The incidence of invasive GAS infections was on average 2.3 per 100,000 per year. Bacteremia with no focal symptoms (27%) was together with erysipelas (20%) the most prevalent clinical diagnoses. Streptococcal toxic shock syndrome occurred in 10% of patients, of which 56% died. The overall case fatality rate within 30 days was 23%. In total, 47 different emm types were identified, of which emm 1, emm 3, emm 4, emm 12, emm 28, and emm 89 were identified in 72% of the 493 available isolates. During the 4-year period the presence of emm 1 increased from 16% in 1999 to 40% in 2002. Concurrently, the presence of emm 3 decreased from 23% in 1999 to 2% in 2002. The emm 1 isolates predominantly carried speA , although the frequency decreased from 94% in 1999 to 71% in 2002, whereas the emm 1-specific prevalence of speC increased from 25 to 53%. In a historical perspective, this could be interpreted as a reemergence of emm 1 and could indicate a possible introduction of a new emm 1 subclone. However, this reemergence did not result in any significant changes in the clinical manifestations during the study period. Our results show the complexity of invasive GAS infections, with time-dependent variations in the incidence and distribution of emm and SAg genes, which emphasizes the need for continuous epidemiological and molecular investigations.