Poster Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

Molecular epidemiology of superficial Streptococcus pyogenes infections in the SToP trial Western Australia (#6)

Emma Pearson 1 , Hannah Thomas 1 2 , Mark Davies 3 , Andrew Hayes 3 , August Mikucki 1 , Janessa Pickering 1 2 , Asha C Bowen 1 2 4 5
  1. The Kids Research Institute Australia, Perth, WA, Australia
  2. School of Biomedical Science, The University of Western Australia, Perth, WA, Australia
  3. Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, Victoria, Australia
  4. Department of Infectious Disease, Perth Childrens Hospital, Perth, WA, Australia
  5. School of Medicine, The University of Western Australia, Perth, WA, Australia

Background:

Remote-living Aboriginal children in northern Western Australia (WA) experience the highest rates of impetigo in the world; this is linked with endemic rates of serious post-infectious sequelae like rheumatic heart disease. However, the molecular epidemiology of superficial Streptococcus pyogenes (GAS) infections (impetigo, pharyngitis) in this region remains undefined. Embedded in the See, Treat, Prevent Skin Sores and Scabies (SToP) Trial,1 this study aimed to characterise the diversity, dynamics and antimicrobial resistance profiles of GAS strains circulating among remote-living children in the Kimberley region of northern WA.

Methods:

Impetigo (IS) and oropharyngeal (OPS) swabs were collected from children attending nine Kimberley schools during three baseline surveillance visits (April–December, 2019). When present, GAS was isolated and whole genome sequenced to derive emm and MLST type, and antimicrobial resistance profiles. These data were integrated with SToP Trial meta- and clinical data for comprehensive epidemiological analysis.

Results:

182 GAS isolates were identified from IS (n=116/346) and OPS (n=66/356). Sequenced isolates (n=180) showed high genetic diversity (Simpson’s Index = 0.9); 27 unique emm types identified. The prevalence of strains varied across surveillance visits. GAS strains mostly belonged to emm clusters E1-6 (n=100/180) and D1-5 (n=53/180). emm cluster E and D strains were identified from IS and OPS, while emm cluster A-C strains were predominantly from OPS.

Conclusion: 

The high prevalence of impetigo in the study population coincided with a high diversity of circulating GAS strains. Strains mostly belong to emm clusters D and E, further informing vaccine design to include skin protection.

  1. Mullane MJ, Barnett TC, Cannon JW, Carapetis JR, Christophers R, Coffin J, Jones MA, Marsh JA, Mc Loughlin F, O'Donnell V, Pavlos R, Smith B, Steer AC, Tong SYC, Walker R, Bowen AC. SToP (See, Treat, Prevent) skin sores and scabies trial: study protocol for a cluster randomised, stepped-wedge trial for skin disease control in remote Western Australia. BMJ Open. 2019 Sep 24;9(9):e030635. doi: 10.1136/bmjopen-2019-030635. PMID: 31551385; PMCID: PMC6773324.