Epidemiology and emm types of invasive group A streptococcal infections in Finland, 2008-2013

Invasive Streptococcus pyogenes (group A streptococcus, GAS) infections are a major global cause of morbidity and mortality. We analysed the surveillance data on invasive GAS and the microbiological characteristics of corresponding isolates to assess the incidence and emm type distribution of invasive GAS infections in Finland. Cases defined as patients with isolations of blood and cerebrospinal fluid S. pyogenes are mandatorily notified to the National Infectious Disease Registry and sent to the national reference laboratory for emm typing. Antimicrobial data were collected through the network including all clinical microbiology laboratories. Pulsed-field gel electrophoresis (PFGE) analysis was performed to assess clonality. In total, 1165 cases of invasive GAS were reported in Finland during 2008-2013; the median age was 52 years (range, 0-100) and 54 % were male. The overall day 7 case fatality rate was 5.1 % (59 cases). The average annual incidence was 3.6 cases per 100,000 population. A total of 1122 invasive GAS isolates (96 %) were analysed by emm typing; 72 different emm types were identified, of which emm28 (297 isolates, 26 %), emm89 (193 isolates, 12 %) and emm1 (132 isolates, 12 %) were the most common types. During 2008-2013, an increase of erythromycin resistance (1.9 % to 8.7 %) and clindamycin (0.9 % to 9.2 %) was observed. This resistance increase was in parallel with the introduction of a novel clone emm33 into Finland. The overall incidence of invasive GAS infections remained stable over the study period in Finland. We identified clonal spread of macrolide-resistant invasive emm33 GAS type, highlighting the importance of molecular surveillance.