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Differences between macrolide-resistant and -susceptible Streptococcus pyogenes: importance of clonal properties in

C Silva-Costa1, A Friães, M Ramirez

  • 1Instituto de Microbiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.

Antimicrobial Agents and Chemotherapy
|August 22, 2012
PubMed

Insights

Macrolide resistance in Streptococcus pyogenes (group A streptococci) showed declining trends. Resistant strains exhibited distinct population dynamics separate from susceptible strains, indicating unique evolutionary patterns.

Area of Science:

  • Microbiology
  • Epidemiology
  • Molecular Typing

Background:

  • Macrolide resistance in Streptococcus pyogenes (group A streptococci, GAS) has been a growing concern.
  • A decline in macrolide resistance among GAS in Portugal was observed between 1999 and 2006.
  • Changes in resistance phenotypes and clonal composition accompanied this decline.

Purpose of the Study:

  • To investigate if the population dynamics of macrolide-resistant GAS mirrored those of the overall GAS population.
  • To characterize both susceptible and resistant GAS strains causing tonsillopharyngitis in Portugal from 2000 to 2005.

Main Methods:

  • Pulsed-field gel electrophoresis (PFGE) was employed for molecular typing of GAS isolates.
  • PFGE was used to predict emm types and differentiate clones associated with macrolide resistance and susceptibility.
  • Analysis focused on isolates recovered between 2000 and 2005.

Main Results:

  • PFGE profiling effectively predicted emm type and distinguished resistant from susceptible clones within emm types.
  • Specific PFGE clusters were significantly associated with either macrolide susceptibility or resistance.
  • No evidence of frequent horizontal gene transfer of macrolide resistance determinants was found.
  • The macrolide-resistant GAS population displayed lower diversity compared to susceptible isolates.

Conclusions:

  • The macrolide-resistant GAS population exhibits distinct population dynamics, separate from susceptible strains.
  • These findings suggest independent evolutionary trajectories for resistant and susceptible GAS populations.
  • Understanding these dynamics is crucial for managing antibiotic resistance in GAS infections.

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