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Published on: November 23, 2012
emm Gene distribution among erythromycin-resistant and -susceptible Italian isolates of Streptococcus pyogenes
Claudia Zampaloni1, Paola Cappelletti, Manuela Prenna
1Department of Molecular Cellular Animal Biology, University of Camerino, 62032 Camerino, Italy. sandro.ripa@unicam.it
Abstract:
The phenotypes and genetic determinants for macrolide resistance were determined for 167 erythromycin-resistant Streptococcus pyogenes strains. A cMLS phenotype was shown in 18% of the erythromycin-resistant strains, while inducible resistance was apparent in 31% and the M phenotype was apparent in 50%. The emm gene type of this set of resistant isolates and that of 48 erythromycin-sensitive isolates were determined. emm2 and emm48 were recorded only in the resistant strains of the M phenotype, while approximately all of the strains harboring the emm22 gene had the cMLS phenotype. More than 80% of the emm89-positive strains had the iMLS phenotype, and the same portion of emm4 strains presented the M phenotype. emm3 is recorded only among sensitive strains. The distribution of frequencies of the genetic determinant for the virulence factor M protein was significantly different both among organisms of different types of resistance and between resistant and sensitive populations of S. pyogenes under study.
Insights
This study investigated macrolide resistance in Streptococcus pyogenes, finding distinct genetic links between emm gene types and resistance phenotypes. Understanding these associations is crucial for managing antibiotic resistance in this pathogen.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Streptococcus pyogenes is a significant human pathogen.
- Macrolide antibiotics are crucial for treating S. pyogenes infections.
- Emergence of macrolide resistance threatens treatment efficacy.
Purpose of the Study:
- To determine macrolide resistance phenotypes in erythromycin-resistant S. pyogenes.
- To identify genetic determinants, specifically emm gene types, associated with these resistance phenotypes.
- To analyze the distribution of emm genes in both resistant and sensitive S. pyogenes populations.
Main Methods:
- Phenotypic characterization of macrolide resistance (cMLS, iMLS, M phenotypes).
- emm gene typing of 167 erythromycin-resistant and 48 erythromycin-sensitive S. pyogenes isolates.
- Statistical analysis of emm gene distribution across resistance phenotypes and populations.
Main Results:
- Prevalence of resistance phenotypes: 18% cMLS, 31% iMLS, 50% M.
- Specific emm gene types (emm2, emm48) were exclusively found in M phenotype resistant strains.
- emm22 associated with cMLS, emm89 with iMLS, and emm4 with M phenotypes.
- emm3 was only identified in sensitive strains.
- Significant differences in M protein virulence factor gene distribution were observed between resistance groups and sensitive strains.
Conclusions:
- Distinct emm gene types correlate with specific macrolide resistance mechanisms in S. pyogenes.
- The genetic background, including emm type and M protein distribution, influences macrolide resistance.
- These findings are vital for epidemiological surveillance and guiding antimicrobial therapy strategies against S. pyogenes.
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