Invasive Group A Streptococcal Disease Surveillance in Canada, 2020

Background: Invasive group A streptococcal (iGAS) disease (caused by ) has been a nationally notifiable disease in Canada since 2000. This report summarizes the demographics, types and antimicrobial resistance of iGAS infections in Canada in 2020.

Methods: The Public Health Agency of Canada's National Microbiology Laboratory (Winnipeg, Manitoba) collaborates with provincial and territorial public health laboratories to conduct national surveillance of invasive typing was performed on all isolates using the Centers for Disease Control and Prevention sequencing protocol. Antimicrobial susceptibilities were determined using Kirby-Bauer disk diffusion according to Clinical and Laboratory Standards Institute guidelines. Population-based iGAS disease incidence rates up to 2019 were obtained through the Canadian Notifiable Disease Surveillance System.

Results: Overall, the incidence of iGAS disease in Canada has increased from 4.0 to 8.1 cases per 100,000 population from 2009 to 2019. The 2019 incidence represents a slight decrease from the 2018 rate of 8.6 cases per 100,000 population. A total of 2,867 invasive isolates that were collected during 2020 are included in this report, representing a decrease from 2019 (n=3,194). The most common types in 2020 were 49 (16.8%, n=483) and 76 (15.0%, n=429), both increasing significantly in prevalence since 2016 (<0.001). The former most prevalent type, 1, decreased to 7.6% (n=217) in 2020 from 15.4% (n=325) in 2016. Antimicrobial resistance rates in 2020 included 11.5% resistance to erythromycin, 3.2% resistance to clindamycin and 1.6% nonsusceptibility to chloramphenicol.

Conclusion: Though the number of collected invasive isolates decreased slightly in 2020 in comparison to previous years, iGAS disease remains an important public health concern. The distribution in Canada has been subtly shifting over the past five years, away from common and well-known 1 and towards 49 and 76. It is important to continue surveillance of in Canada to monitor expanding replacement types, as well as outbreak clones and antimicrobial resistance.