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Published on: May 23, 2021
Variation in M protein production among Streptococcus pyogenes strains according to emm genotype
Masakado Matsumoto1, Masahiro Suzuki, Kaoru Hirose
1Department of Microbiology and Medical Zoology Aichi Prefectural Institute of Public Health, Aichi, Japan. masakado_matsumoto@pref.aichi.lg.jp
Abstract:
M protein is an important virulence determinant in Streptococcus pyogenes, but the amounts of M protein in various strains of the species remain to be elucidated. To assess the amount of M protein in strains of each emm genotype, dot blot analysis was performed on 141 clinically isolated strains. Among the cell membrane-associated proteins, M protein was present in greater quantities in the emm1, 3, and 6 strains than in the other emm strains. In addition three strains, one each of the emm1, 3, and 6 types, showed prolific M protein production (M protein-high producers). These three emm genotypes are frequently isolated in clinical practice. Sequencing of the csrRS gene, one of the two-component signal transduction systems implicated in virulence, was performed on 25 strains bearing different amounts of M protein. CsrS mutations, in contrast to CsrR protein, were detected in 11 strains. The M protein-high producer strain of emm1 type carried two amino acid substitutions, whereas the other three emm1 strains carried only one substitution each. The M protein-high producer expressed its emm gene more strongly than the corresponding M protein-low producer did according to TaqMan RT-PCR. These observations suggest that the accumulation of amino acid substitutions in CsrS protein may contribute, at least in part, to the large amount of M protein production seen in several emm genotypes.
Insights
Streptococcus pyogenes M protein production varies by emm genotype. Accumulation of amino acid substitutions in the CsrS protein may contribute to high M protein levels in certain strains.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- M protein is a key virulence factor in Streptococcus pyogenes.
- Understanding M protein quantity across different emm genotypes is crucial for assessing virulence.
- The csrRS gene, a two-component system, is implicated in regulating virulence factors.
Purpose of the Study:
- To quantify M protein amounts in various Streptococcus pyogenes emm genotypes.
- To investigate the role of csrRS gene mutations in M protein production.
- To correlate M protein levels with emm genotype and csrRS mutations.
Main Methods:
- Dot blot analysis of M protein in 141 clinical isolates.
- Sequencing of the csrRS gene in 25 strains with varying M protein levels.
- TaqMan RT-PCR to measure emm gene expression.
Main Results:
- M protein was more abundant in emm1, 3, and 6 strains.
- Three strains (emm1, emm3, emm6) were identified as high M protein producers.
- CsrS mutations were found in 11 strains; high producers often had multiple amino acid substitutions in CsrS.
- High M protein producers showed stronger emm gene expression.
Conclusions:
- M protein quantity is influenced by emm genotype in Streptococcus pyogenes.
- Mutations in CsrS, particularly accumulated amino acid substitutions, are associated with increased M protein production.
- These findings suggest a mechanism for enhanced virulence in specific S. pyogenes strains.
