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Group A streptococcal Vir types are M-protein gene (emm) sequence type specific
D L Gardiner1, A M Goodfellow, D R Martin
1Menzies School of Health Research, Darwin, Australia. don@menzies.su.edu.au
Abstract:
The M-protein genes (emm genes) of 103 separate impetiginous Streptococcus pyogenes isolates were sequenced and the sequence types were compared to the types obtained by Vir typing. Vir typing is based on restriction fragment length polymorphism (RFLP) analysis of a 4- to 7-kb pathogenicity island encoding emm and other virulence genes. By using both HaeIII and HinfI to generate RFLP profiles, complete concordance between Vir type and emm sequence type was found. Comparison of the emm sequences with those in GenBank revealed new sequence types sharing less than 90% identity with known types. Diversity in the emm sequence was generated by corrected frameshift mutations, point mutations, and small in-frame mutations.
Insights
Sequencing Streptococcus pyogenes M-protein (emm) genes revealed new types and confirmed Vir typing accuracy. This study enhances understanding of emm gene diversity in impetigo isolates.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Streptococcus pyogenes causes impetigo and other skin infections.
- M-protein genes (emm) are key virulence factors and targets for typing.
- Vir typing, a restriction fragment length polymorphism (RFLP) method, is used for S. pyogenes classification.
Purpose of the Study:
- To sequence emm genes from impetiginous S. pyogenes isolates.
- To compare emm sequence types with existing Vir typing results.
- To identify novel emm sequence types and understand their genetic diversity.
Main Methods:
- Sequencing of emm genes from 103 S. pyogenes isolates.
- Vir typing using RFLP analysis of a pathogenicity island with HaeIII and HinfI restriction enzymes.
- Comparison of obtained emm sequences with GenBank database.
Main Results:
- Complete concordance was observed between Vir type and emm sequence type.
- New emm sequence types were identified, showing less than 90% identity to known types.
- Genetic diversity in emm sequences resulted from frameshift, point, and in-frame mutations.
Conclusions:
- emm gene sequencing is a reliable method for S. pyogenes typing, correlating with Vir typing.
- The study identified novel emm types, expanding the known genetic diversity of S. pyogenes.
- Understanding emm gene mutations provides insights into bacterial evolution and virulence.