Circulating emm types of Streptococcus pyogenes in Scotland: 2011-2015.

Streptococcus pyogenes [Group A Streptococcus (GAS)] can colonize skin and mucosal membranes giving rise to carriage and localized and/or systemic infections that can range in severity (Luca-Harari et al., 2009; Fiedler et al., 2015). Traditionally, S. pyogenes isolates were serotyped using Mand T-factor-specific anti-sera that have been replaced by M genotyping (emm typing) (Johnson et al., 2006). The M protein is a major virulence factor of GAS and is a hair-like projection from the bacterial cell surface, where it facilitates resistance to complementmediated killing and aids in bacterial evasion of phagocytosis (Bessen et al., 2008). The M protein is also essential for the bacterial attachment to keratinocytes that play a significant role in infections originating at the skin surface (Biswas et al., 2001). M genotyping has made international comparisons possible and identified a worldwide perspective of strain variation. There are over 200 recorded emm types and subtypes that help in the identification of outbreaks and cluster management (CDC, 2008). In Scotland, between 1999 and 2005, there was a rise in invasive GAS infections from 50 to 200 per year (HPS Weekly Report, 2006), a finding consistent with observations from other European countries (Luca-Harari et al., 2009; Koutouzi et al., 2015). This study reports on the distribution of GAS emm types and subtypes from invasive and non-invasive sites over a 4-year period and further identifies the most susceptible age/sex range for invasive disease.