Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

A new diagnostic approach for an old pathogen: is saliva the solution for Strep A?   (94040)

Anuk Indraratna 1 2 3 , Sacha Mytton 4 , Joshua Osowicki 5 6 7 , Andrew Steer 5 6 7 , Danielle Skropeta 1 2 3 , Martina Sanderson-Smith 1 2 3
  1. University of Wollongong, Wollongong, NSW , Australia
  2. Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia
  3. Molecular Horizons, School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales, Australia
  4. Genetic Signatures Limited, Sydney, NSW, Australia
  5. Tropical Diseases, Murdoch Children's Research Institute, Melbourne, Victoria, Australia
  6. Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
  7. Infectious Diseases Unit, Department of General Medicine, The Royal Children's Hospital Melbourne, Melbourne, Victoria, Australia

Group A Streptococcus (S. pyogenes; Strep A; GAS) has re-emerged in recent years as a significant human oropharyngeal pathogen and is responsible for a diverse range of tissue infections and auto-immune sequelae. In addition to invasive Strep A infections, immune complications following superficial infection are a significant cause of human mortality. 

The contemporary diagnostic paradigm in Australia involves culture on blood agar which is time-consuming, low-throughput, and relies on invasive throat swabbing of patients. Although molecular approaches are becoming more widespread, the potential of saliva as a diagnostic fluid for Strep A infection remains unexplored. Here, we demonstrate the development of a novel, robust, highly specific and sensitive saliva-based PCR assay using patented 3baseTM technology from Genetic Signatures Limited (Sydney, Australia). Assays based on three highly conserved regions of the Strep A core genome (two within spy1258; speB) were developed and optimised, with the speB assay identified as the best-performing. 

This assay has been validated on clinical saliva samples generated from a controlled model of human infection (CHIVAS), in which baseline, acute, and convalescent saliva samples were collected from healthy adult participants challenged with emm75 Strep A. In addition to providing strong evidence of the utility of saliva-based diagnostics, validation in this cohort also provides powerful insights into the onset and duration of PCR positivity in the context of an acute infection.