Virtual Poster 21st Lancefield International Symposium for Streptococci and Streptococcal Diseases 2022

qPCR enhances detection of Strep A in skin and throat specimens from children at higher risk of disease (#414)

Bernadette Wong 1 , Timothy C. Barnett 1 2 , Scott Winslow 1 , Dylan D. Barth 1 2 , Jonathan R. Carapetis 1 2 3 , Asha C. Bowen 1 2 3 , Janessa L. Pickering 1 2
  1. Wesfarmer’s Centre for Vaccines and Infectious Diseases, Telethon Kids Institute, Nedlands, Western Australia, Australia
  2. Centre for Child Health Research, University of Western Australia, Nedlands, Western Australia, Australia
  3. Department of Infectious Diseases, Perth's Children Hospital, Nedlands, Western Australia, Australia

Background:

Children living in remote Australian communities bear a disproportionately high burden of Strep A diseases. Accurate Strep A laboratory detection methods are required to understand the burden of disease; however, the application of Strep A molecular techniques is largely under-researched in endemic populations. We aimed to further interrogate samples from a cohort of  remote-living school children enrolled in The Missing Piece Surveillance Study, based in the Kimberley, Western Australia.

 

Methods:

Demographics, clinical data and specimens were obtained during the school-based surveillance programme. In 2019, 470 skin and throat swabs stored in Skim-Milk-Glucose-Glycerol-Broth were collected and underwent gold standard Strep A culture. We optimised and performed Strep A DNA extraction and speB quantitative PCR (qPCR) on a subset of skin (n=32) and throat t(n=289) to determine Strep A bacterial load, and evaluated against culture results.

 

Results:

Strep A qPCR showed a sensitivity and specificity of 97.70% (95% CI [88.2 to 99.6]) and 77.50% (95% CI [71.9 to 82.3]) for throat swabs relative to culture results. The reduced specificity resulted from an additional 55 culture negative throat samples which were Strep A positive by qPCR, demonstrating increased detection capability and potential for high-throughput analysis of large cohorts. Furthermore, speB qPCR resulted in a shorter turnaround time compared to culture. speB Cq values did not differentiate Strep A pharyngitis and carriage (p=0.938).

 

Conclusions:

Enhanced detection with molecular technology should be considered in surveillance of Strep A infection. Detection and prevention of Strep A disease remains crucial to Rheumatic Heart Disease elimination.