Poster Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

Household molecular epidemiology of Streptococcus pyogenes carriage and infection in The Gambia (#37)

Gabrielle de Crombrugghe 1 2 3 , Edwin P Armitage 3 4 5 , Alexander J Keeley 3 4 6 7 , Elina Senghore 3 , Fatoumata Camara 3 , Musukoi Jammeh 3 , Amat Bittaye 3 , Haddy Ceesay 3 , Isatou Ceesay 3 , Bunja Samateh 3 , Muhammed Manneh 3 , Gwenaëlle Botquin 2 , Dalila Lakhloufi 2 , Valerie Delforge 2 , Saikou Y Bah 3 6 8 , Jennifer N Hall 6 7 8 , Lionel Schiavolin 2 , Claire E Turner 6 8 , Michael Marks 4 9 10 , Thushan I de Silva 3 6 7 , Anne Botteaux 2 , Pierre R Smeesters 1 2 11 12
  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. Vaccines and Immunity Theme, Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
  4. Department of Clinical Research, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
  5. Population Health Sciences, Bristol Medical School, University of Bristol, BS8 2PN, UK, Bristol
  6. Florey Institute of Infection, University of Sheffield, Sheffield, UK
  7. Division of Clinical Medicine, School of Medicine and Population Health, University of Sheffield, Sheffield, UK, Sheffield
  8. School of Biosciences, University of Sheffield, Sheffield, UK , Sheffield
  9. Hospital for Tropical Diseases, University College London Hospital, London, UK
  10. Division of Infection and Immunity, University College London, London, UK
  11. Tropical Diseases Research Group, Murdoch Children’s Research Institute, Melbourne, Victoria, Australia
  12. Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia

Background

High burden of Streptococcus pyogenes (S pyogenes) disease is seen in Africa which is also the continent with the least epidemiological data on circulating strains. Our aim is to better characterise emm-types and emm-clusters associated with carriage and disease in a setting with high rheumatic heart disease (RHD) burden, a peri-urban area in The Gambia.

Methods

A one-year household cohort study was conducted in 2021-2022, recruiting 442 healthy participants from 44 households, looking for S pyogenes carriage and non-invasive infection. Pharyngeal and normal skin swabs were collected to assess carriage, pharyngitis and pyoderma swabs were captured to asses infection. Cultured isolates underwent emm-typing and were compared with a similar collection from 2018. Simpson's reciprocal index (SRI) was used to measure diversity.

Results

221 isolates showed a positive culture for S pyogenes, representing 52 emm-types and 16 emm-clusters, with 4 over-represented clusters comprising 64.7% of the isolates. emm-type diversity was high (SRI 29.3, 95% CI: 24.8-36.0). Looking at emm-type and intra-individual transmission, we found frequent transmission between pyoderma and intact skin, and evidence of A comparison with pyoderma isolates collected in 2018 revealed no significant changes in circulating emm-clusters.

Conclusion

This study provides the first molecular analysis of skin and throat isolates prospectively collected from carriage and disease in Africa. In this RHD-endemic setting, pyoderma and skin carriage represent an important S pyogenes reservoir and should be included in further studies and public health interventions.