Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

A rapid molecular detection tool for toxigenic M1UKStreptococcus pyogenes (#7)

Stephan Brouwer 1 , Swairindhree Das 2 , Andrew J Hayes 3 , Olivia M Bertolla 1 , Mark R Davies 3 , Mark J Walker 1 , David M Whiley 2 4 , Adam D Irwin 2 4 5 , Jacob A Tickner 2 4
  1. Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
  2. University of Queensland Centre for Clinical Research, The University of Queensland, Brisbane, QLD, Australia
  3. Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia
  4. Queensland Paediatric Infectious Diseases Sakzewski Laboratory, Centre for Children’s Health Research, Queensland Children’s Hospital, Brisbane, QLD, Australia
  5. Infection Management and Prevention Service, Queensland Children’s Hospital, Brisbane, Queensland, Australia

Background:

The gradual replacement of the Streptococcus pyogenes (β-hemolytic Group A Streptococcus) M1global genotype by a newly emergent M1UK variant in several countries is a global public health threat and its epidemic potential warrants increased surveillance. M1UK differs from the progenitor M1global genotype by 27 single nucleotide polymorphisms (SNPs) and is characterised by increased speA superantigen expression in vitro, resulting from a single SNP (+5 G > C) in the 5’ transcriptional leader sequence of the adjacent upstream transfer-messenger RNA gene ssrA.

Methods:

An ssrA allele-specific real-time PCR assay was developed to allow for the rapid and reliable detection of M1UK strains. The assay was used in combination with whole-genome sequencing to screen S. pyogenes clinical isolates obtained from 51 pharyngeal swab cultures.

Results:

Emm1 was the most prevalent S. pyogenes emm serotype in this set of clinical isolates, with M1UK being the dominant emm1 genotype. The assay accurately detected M1UK strains via identification of the ssrA +5 G > C SNP. Whole genome sequencing revealed continued presence of Australian M1UK sub-lineages that contain an extended toxin gene repertoire associated with epidemic scarlet fever-causing S. pyogenes in Asia.

Conclusions:

Our study establishes the ssrA SNP as a suitable target for detection of the toxigenic M1UK variant, and confirms the maintenance of M1UK strains in Queensland, Australia. This assay can be rapidly deployed in clinical laboratories and provides a valuable, cost-effective tool to enhance surveillance of the expanding M1UK variant. 

 

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