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Macrolide-resistant Streptococcus pyogenes in the United States, 2002-2003

Sandra S Richter1, Kristopher P Heilmann, Susan E Beekmann

  • 1Department of Pathology, University of Iowa Carver College of Medicine, Iowa City, IA 52242-1009, USA. sandra-richter@uiowa.edu

Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America
|August 5, 2005
PubMed
Abstract

Insights

Macrolide-resistant Streptococcus pyogenes strains are present in the US, with resistance mechanisms including ermA and mefA genes. While the overall population is small, certain clones show potential for expansion, highlighting the need for ongoing surveillance.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Reports indicate rising macrolide-resistant Streptococcus pyogenes in the US.
  • Understanding resistance mechanisms and genetic relatedness is crucial for public health.

Purpose of the Study:

  • To determine antimicrobial susceptibility of S. pyogenes isolates nationwide.
  • To identify mechanisms and genetic links among macrolide-resistant strains.

Main Methods:

  • Analyzed 1885 S. pyogenes isolates from 45 US centers (2002-2003).
  • Assessed susceptibility to various antibiotics.
  • Determined macrolide resistance phenotypes and genotypes (PCR, sequencing).
  • Characterized resistant isolates using PFGE and emm typing.

Main Results:

  • Resistance detected to erythromycin (6.8%), azithromycin (6.9%), and clarithromycin (6.6%).
  • Macrolide resistance phenotypes were MLSB (56%) and M (44%).
  • Genotypes ermA and mefA were prevalent, linked to specific resistance phenotypes.
  • Erythromycin-resistant isolates clustered into major clones associated with specific emm types and resistance genes.

Conclusions:

  • The population of macrolide-resistant S. pyogenes in the US is currently small.
  • However, several large clones exist with the potential for future expansion.

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