Prevalence and characterization of invasive isolates of Streptococcus pyogenes with reduced susceptibility to

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Jeff Powis1, Allison McGeer, Carla Duncan

  • 1Department of Microbiology, Toronto Medical Laboratories, Mount Sinai Hospital, 600 University Ave., Toronto, Ontario, Canada M5G 1X5.

Antimicrobial Agents and Chemotherapy
|April 28, 2005
PubMed

Insights

Group A Streptococcus (GAS) isolates showed no levofloxacin resistance. A slight increase in levofloxacin MICs was observed in Canadian isolates between 1992-1993 and 2003, linked to parC mutations.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Invasive group A Streptococcus (GAS) infections pose a significant public health concern.
  • Fluoroquinolones are important antibiotics for treating bacterial infections.
  • Monitoring antimicrobial susceptibility is crucial for effective treatment strategies.

Purpose of the Study:

  • To assess fluoroquinolone susceptibility in invasive group A Streptococcus isolates from Ontario, Canada.
  • To determine trends in susceptibility over time.
  • To investigate potential genetic mechanisms associated with reduced susceptibility.

Main Methods:

  • Invasive group A Streptococcus isolates collected in Ontario, Canada during 1992-1993 and 2003 were tested.
  • Fluoroquinolone susceptibility testing was performed.
  • Minimum Inhibitory Concentrations (MICs) for levofloxacin were determined.
  • parC mutations and serotype M6 were analyzed in isolates with elevated MICs.

Main Results:

  • No isolates were nonsusceptible to levofloxacin.
  • A small proportion of isolates exhibited a levofloxacin MIC of 2 µg/ml in both periods (1.3% in 1992-1993 and 4.4% in 2003).
  • All nine isolates with a levofloxacin MIC of 2 µg/ml possessed parC mutations; eight were serotype M6.

Conclusions:

  • Levofloxacin remains a viable treatment option for invasive group A Streptococcus infections in the studied Canadian population.
  • The emergence of parC mutations in a small subset of isolates warrants continued surveillance.
  • Serotype M6 may be associated with reduced susceptibility to levofloxacin in group A Streptococcus.

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