F2F Poster 21st Lancefield International Symposium for Streptococci and Streptococcal Diseases 2022

Association between streptococcal pyrogenic exotoxin A (SpeA) expression and transcriptional regulatory gene mutations in streptococcus pyogenes (#108)

Ho Kwong Li 1 2 , Ana Vieira 1 , Xiangyun Zhi 1 , Michael Tay 1 , Hanqi Li 1 , Theresa Lamagni 3 , Juliana Coelho 3 , Elita Jauneikaite 1 , Claire Turner 4 , Shiranee Sriskandan 1 2
  1. Department of Infectious Disease, Imperial College London, London, United Kingdom
  2. MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
  3. National Infection Service, UK Health Security Agency, London, United Kingdom
  4. Department of Molecular Biology & Biotechnology, University of Sheffield, Sheffield, United Kingdom

Background

A new emm1 sublineage (M1UK) emerged in England characterised by increased SpeA production and 27 SNPs in the core genome including 3 SNPs in rofA. Regulation of SpeA expression is poorly understood. We compared SpeA expression between emm types that commonly possess the spea gene and determined associations with regulatory gene mutations.

 

Methods

All S. pyogenes throat isolates that encode spea collected in northwest London in 2009-2016 were included (n=223). Expression of SpeA was quantified by real-time PCR and western blot. Mutations in known regulators were linked to SpeA production. Invasive emm1 S. pyogenes (n=40), comprising M1UK and non-M1UK isolates were also analysed.

 

Results

Transcription of spea was greatest in emm3 isolates, while almost undetectable in emm22. Though spea transcripts was detected in emm6 and emm28, protein expression was low. A bimodal pattern of SpeA expression was observed for emm1 consistent with the known phenotype of M1UK. Analysis of transcriptional regulators pointed to a role for covRS, rocA, rgg, and rofA in SpeA expression. SNP in RofA alone were insufficient to account for SpeA over-expression, as SpeA did not differ between non-M1UK isolates and intermediate isolates with 13/27 SNPs (including RofA). CovRS mutations were associated with increased SpeA expression in all invasive emm1 isolates including M1UK.

 

Conclusions

There are emm-type specific differences in SpeA production that might be explained by differences in core genome regulators. CovRS mutations play the largest detectable role in SpeA expression in this sample. There is a notable mismatch between transcription and detectable protein expression in some genotypes.