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A study on erm(B)-mediated MLS resistance in Streptococcus pyogenes clinical isolates
Silvia Rombini1, Dezemona Petrelli, Elisabetta Bolli
1School of Biosciences and Biotechnology, University of Camerino, via Gentile III da Varano, I-62032 Camerino (MC), Italy.
Diagnostic Microbiology and Infectious Disease
|June 21, 2011
Summary
The macrolide-lincosamide-streptogramin (MLS) resistance in Streptococcus pyogenes is complex. Culture conditions significantly impact MLS resistance expression, not just the erm(B) gene sequence.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Macrolide-lincosamide-streptogramin (MLS) resistance is a significant concern in Streptococcus pyogenes infections.
- The erm(B) gene is a common mechanism conferring MLS resistance.
- Understanding the regulation of erm(B) expression is crucial for effective treatment strategies.
Purpose of the Study:
- To investigate the relationship between the macrolide-lincosamide-streptogramin (MLS) phenotype and the erm(B) gene sequence in Streptococcus pyogenes.
- To determine the influence of different growth conditions on MLS resistance expression.
- To elucidate the regulatory mechanisms controlling erm(B) gene expression.
Main Methods:
- Phenotypic determination of MLS resistance in 30 erm(B)-positive Streptococcus pyogenes isolates using various methods.
- Correlation of MLS phenotype with the sequence of the 5'-untranslated regions of erm(B).
- Analysis of 23S rRNA methylation levels to confirm resistance mechanisms.
- Evaluation of resistance expression under different growth conditions, including varying growth rates and induction periods.
Main Results:
- One-third of the isolates exhibited an unclassifiable MLS phenotype.
- Resistance expression varied with growth phase and conditions; some isolates required induction during logarithmic growth, while others showed resistance constitutively.
- Increasing the growth rate shifted resistance from a constitutive to an inducible pattern.
- The erm(B)-5'-untranslated region sequences were highly similar (99%) across isolates, suggesting sequence alone does not fully explain the observed phenotypes.
Conclusions:
- The MLS phenotype in erm(B)-positive Streptococcus pyogenes is significantly influenced by environmental and culture conditions.
- Regulation of erm(B) expression and MLS resistance is complex and not solely dependent on the erm(B)-5'-untranslated region sequence.
- Further research is needed to fully understand the regulatory factors governing MLS resistance in S. pyogenes.
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