Relation between emm types and virulence gene profiles among Bulgarian Streptococcus pyogenes clinical isolates

Abstract

Background: The Streptococcus pyogenes emm gene, which encodes M protein, is an important epidemiological marker. The aim of this study is to determine the emm genotypes of Bulgarian clinical streptococccal isolates in 2014–2018 and to evaluate their relationship with virulence genes profiling and disease types.

Methods: PCR and sequencing were used for emm genotyping of 182 S. pyogenes clinical isolates according to the protocol of the Centre for Disease Control and Prevention. PCR was used to investigate the virulence factors.

Results: We identified 15 emm types and eight clusters. Five main clusters with eight emm types were predominant: cluster A-C3 (emm1) – 24.7%, A-C5 (emm3) – 19.2%, E1 (emm4) – 11.0%, A-C4 (emm12) – 11.0% and E4 (emm2,28,77,89) – 20.9%. There were two novel subtypes: emm3.132 and emm3.133. The investigated strains with emm3 genotypes were common in sterile site infections (invasive ones) and types emm4 and emm12, in skin and mucosal infections. More than 60% of the major cluster A-C3 (emm1; emm1.33; emm1.6) members possessed many genes for streptococcal pyrogenic exotoxins that act as super-antigens and bring about potentially higher virulence.

Conclusion: The present study described two novel emm3 subtypes. To the best of our knowledge, this study is the first that describe the emm type spectrum of Bulgarian S. pyogenes clinical isolates and associated virulence factors. Monitoring of the S. pyogenes pathogenic potential and epidemiology can lead to better knowledge and higher possibility for prevention and eradication of complications of streptococcal infections.

Keywords:

• Streptococcus pyogenes
• emm genotypes
• virulence factors

Acknowledgements

The authors thank Prof. T. Stoeva (Head of Department of Microbiology and Virology, Faculty of Medicine, Medical University, Varna, Bulgaria; University Hospital ‘St. Marina’) and Dr Magda Joneva (Head of Microbiology Department, Tokuda Hospital, Sofia, Bulgaria), who provided some of the isolates.

Disclosure statement

All authors declare no potential conflicts of interest.

Additional information

Funding

This study was supported by the Medical University of Sofia (Council of Medical Science) under Project number 8263/2016 and Grant number D-56/2017.