Changes in emm types and superantigen gene content of Streptococcus pyogenes causing invasive infections in Portugal

Fluctuations in the clonal composition of Group AStreptococcus(GAS) have been associated with the emergence of successful lineages and with upsurges of invasive infections (iGAS). This study aimed at identifying changes in the clones causing iGAS in Portugal. Antimicrobial susceptibility testing,emmtyping and superantigen (SAg) gene profiling were performed for 381 iGAS isolates from 2010–2015. Macrolide resistance decreased to 4%, accompanied by the disappearance of the M phenotype and an increase of the iMLSBphenotype. The dominantemmtypes were:emm1 (28%),emm89 (11%),emm3 (9%),emm12 (8%), andemm6 (7%). There were no significant changes in the prevalence of individualemmtypes,emmclusters, or SAg profiles when comparing to 2006–2009, although an overall increasing trend was recorded during 2000–2015 foremm1,emm75, andemm87. Short-term increases in the prevalence ofemm3,emm6, andemm75 may have been driven by concomitant SAg profile changes observed within theseemmtypes, or reflect the emergence of novel genomic variants of the sameemmtypes carrying different SAgs.