Poster Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

M1 and done? Converging on a globally representative set of more and less invasive group a streptococcal strains (#39)

Gabrielle de Crombrugghe 1 2 , Lionel Schiavolin 2 , Joshua Osowicki 3 4 5 , Andrew C Steer 3 4 5 , Anne Botteaux 2 , Pierre R Smeesters 1 2 3 4
  1. Department of Paediatrics, Brussels University Hospital, Academic Children Hospital Queen Fabiola, Université Libre de Bruxelles, Brussels, Belgium
  2. Molecular Bacteriology Laboratory, European Plotkin Institute for Vaccinology, Université Libre de Bruxelles, Brussels, Belgium
  3. Tropical Diseases Research Group, Murdoch Children’s Research Institute, Melbourne, Victoria, Australia
  4. Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
  5. Department of Infectious Diseases, Royal Children’s Hospital Melbourne, Victoria, Australia

Background:

Among over 270 recognized group A streptococccal emm-types, the emm1 lineage is conventionally considered as highly invasive. It is the most frequently identified emm-type from invasive isolates in high-income countries and probably the best characterised strain. Based on a recent systematic review, we aimed to determine whether M1 is among the emm-types with the highest invasiveness ratio worldwide, which could have implications for disease control and vaccine strategies. 

Methods:

We previously conducted a population-based systematic review of global emm-type and emm-cluster distributions (1990–2023), analyzing data from 212 studies across 55 countries (1). We extracted all strains associated with invasive and non-invasive manifestations and inferred relative invasiveness for each emm-type based on the proportion of non-invasive and invasive isolates. Five representative emm-types, spanning non-invasive to highly invasive profiles, were selected to assess streptococcal invasiveness.

Results:

We analyzed 175 epidemiological datasets comprising 59 798 global isolates belonging to 112 emm-types and 30 emm-clusters. Most strains came from high income settings (77.0% of isolates), with overall similar proportion among invasive (75,3%) and non-invasive isolates (79.4%).  The well characterised M1 ranked 39th most invasive given it was also frequently isolated in non-invasive infections.

Conclusion

This study highlights the need for enhanced surveillance in low- and middle-income settings, where the burden of invasive disease is highest. M1 may not be the most intrinsically invasive emm-type at a worldwide population level. Including representative strains from emm-types of varying invasiveness could broaden the scope of future microbiological studies.

 

  1. Smeesters PR, de Crombrugghe G, Tsoi SK, Leclercq C, Baker C, Osowicki J, et al. Global Streptococcus pyogenes strain diversity, disease associations, and implications for vaccine development: a systematic review. Lancet Microbe. 2024;5(2):e181-e93.