Update on invasive group A streptococcus hypervirulent M1<sub>UK</sub> clone in Canada 2024 — ASN Events
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  2. Poster Session 1
  3. Update on invasive group A streptococcus hypervirulent M1UK clone in Canada 2024

Update on invasive group A streptococcus hypervirulent M1UK clone in Canada 2024 (#153)

Gregory Tyrrell 1 , Alyssa R Golden 2 , Averil Griffith 2 , Julianne V Kus 3 , Allison McGeer 4 , Marc-Christian Domingo 5 , Jennifer M Grant 6 , Jessica Minion 7 , Paul Van Caeseele 8 , Guillaume Desnoyers 9 , Elizabeth Simms 10 , Robert Taylor 11 , Xiaofeng Ding 12 , Laura Steven 13 , Jan McFadzen 14 , Courtney Primeau 15 , Irene Martin 2
  1. Provincial Laboratory for Public Health (Microbiology), Edmonton
  2. Public Health Agency of Canada - National Microbiology Laboratory, Winnipeg, MANITOBA, Canada
  3. Public Health Ontario, Toronto
  4. Toronto Invasive Bacterial Diseases Network, Mount Sinai Hospital, Toronto
  5. Laboratoire de santé publique du Québec, Ste-Anne-de-Bellevue
  6. British Columbia Centre for Disease Control, Vancouver
  7. Roy Romanow Provincial Laboratory, Regina
  8. Cadham Provincial Laboratory, Winnipeg
  9. Laboratoire de santé publique du New Brunswick, Moncton
  10. Queen Elizabeth II Health Science Centre, Halifax
  11. Newfoundland Public Health Microbiology Laboratory, St. John's
  12. Queen Elizabeth Hospital, Charlottetown
  13. Stanton Territorial Hospital Laboratory, Yellowknife
  14. Yukon Communicable Disease Control, Government of Yukon, Whitehorse
  15. Centre for Emerging and Respiratory Infections and Pandemic Preparedness, Public Health Agency of Canada, Ottawa

Background: The hypervirulent M1UK lineage of group A Streptococcus (GAS) has been associated with increased notifications of invasive GAS (iGAS) infections. Following increased incidence of iGAS infections worldwide after the COVID-19 pandemic, we previously reported on the distribution of M1UK in Canada up to 2023. Here we provide an update on the prevalence of emm1/M1UK in Canada through 2024.

Methods: Whole genome sequencing (WGS) was performed on 3,567 iGAS isolates collected in 2024 (1,285 emm1). M1UK isolates were identified by mapping WGS reads to reference strain MGAS5005 and identifying 27 single nucleotide variants (SNVs). Core SNV phylogeny was performed using SNVPhyl. Statistical significance was assessed using the Cochran-Armitage trend test.

Results: The prevalence of emm1 in 2024 was high at 25.7%, a similar rate to 2023 (24.2%). During 2024 emm1 prevalence decreased each quarter: 38.2% (January-March), 27.9% (April-June), 15.7% (July-September) and 12.5% (October-December) (P<0.0001). Amongst emm1 isolates, the M1UK lineage has increased in prevalence from 22.4% (2018) to 69.3% (2024, P<0.0001). Despite the decrease in emm1 prevalence in 2024, the proportion of M1UK increased throughout the year, from 68.1% (January-March) to 75.9% (October-December) (P=0.0474). Phylogenetic analysis identified 17 regionally-associated clusters of emm1 (9 M1global, 8 M1UK). Average pairwise SNV distances within clusters were higher for 2024 alone than our previous publication, indicating recent diversification of emm1 in Canada.

Conclusions: Continued genomic surveillance is required to identify whether the M1UK lineage continues to expand and diversify across Canada despite decreases in emm1, and whether new lineages are introduced to the country.

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