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A novel invasive Streptococcus pyogenes variant sublineage derived through recombinational replacement of the emm12

Yvette Unoarumhi1, Morgan L Davis1, Lori A Rowe1

  • 1Centers for Disease Control and Prevention, Biotechnology Core Facility Branch, National Center for Emerging and Zoonotic Infectious Diseases, Division Scientific Resources, Atlanta, GA, USA.

Scientific Reports
|December 6, 2023
PubMed

Insights

Group A Streptococcus (GAS) can acquire new M protein gene types via recombination. Researchers discovered a novel GAS variant (emm82/ST36) that switched from emm pattern A to E, showing increased diversity and antibiotic resistance.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Group A Streptococcus (GAS) exhibits genetic variability, including M protein gene switching (emm switching), which can alter virulence and host adaptation.
  • Understanding emm switching is crucial for tracking GAS evolution and predicting potential outbreaks.

Purpose of the Study:

  • To detect and characterize novel variants of GAS that have undergone emm switching.
  • To investigate the genetic makeup, virulence factors, and antibiotic resistance profiles of newly identified GAS variants.

Main Methods:

  • Screening of 12,596 invasive GAS genomes for strains with differing emm types but identical multilocus sequence types (STs).
  • Whole-genome sequencing and phylogenetic analysis of identified variants.
  • Analysis of specific genes, including M protein (emm) and serum opacity factor (sof), and investigation of genetic recombination events.

Main Results:

  • A novel variant of SOF-positive, emm pattern E, emm82 isolates belonging to ST36 was identified. This contrasts with the previously known SOF-negative, emm pattern A, emm12 association for ST36.
  • The emm82/ST36 isolates were genetically related, sharing a common emm82-containing recombinational fragment and exhibiting a corrected sof12 gene for SOF-positive phenotype.
  • These isolates demonstrated significant macrolide resistance (12/16), diverse core genomic arrangements, and multiple combinations of virulence and resistance determinants, with phylogenetic analysis placing them within an antibiotic-resistant lineage of ST36.

Conclusions:

  • This study documents the emergence of a rapidly diversifying GAS variant, representing the first confirmed instance of an emm pattern A strain switching to an emm pattern E strain.
  • The findings highlight the dynamic nature of GAS evolution through genetic recombination and the potential for new variants to acquire significant antibiotic resistance and virulence traits.

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