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An intrinsic pattern of reduced susceptibility to fluoroquinolones in pediatric isolates of Streptococcus pyogenes

S Steve Yan1, Paul C Schreckenberger, Xiaotian Zheng

  • 1Food and Drug Administration, DHHS, Rockville, MD 20855, USA.

Diagnostic Microbiology and Infectious Disease
|June 17, 2008
PubMed

Insights

Pediatric Streptococcus pyogenes isolates show reduced fluoroquinolone susceptibility due to parC mutations. Monitoring genetic changes in parC and gyrA can predict high-level resistance emergence.

Area of Science:

  • Microbiology
  • Genetics
  • Pharmacology

Background:

  • Fluoroquinolones are critical antibiotics.
  • Emergence of antimicrobial resistance is a growing concern.
  • Understanding resistance mechanisms in pediatric pathogens is vital.

Purpose of the Study:

  • To investigate fluoroquinolone susceptibility in pediatric Streptococcus pyogenes isolates.
  • To identify genetic mutations associated with reduced susceptibility.
  • To compare genotypic and phenotypic resistance patterns.

Main Methods:

  • Disc diffusion and Etest for susceptibility testing.
  • Analysis of point mutations in parC and gyrA genes.
  • Molecular typing including M/emm typing, rep-PCR, and PFGE.

Main Results:

  • Nine percent of isolates exhibited reduced susceptibility to fluoroquinolones.
  • A single point mutation (Ser-79) in parC was linked to reduced susceptibility.
  • PFGE with SgrAI was more discriminatory than SmaI for strain typing.

Conclusions:

  • A population of pediatric S. pyogenes with intrinsic reduced fluoroquinolone susceptibility exists.
  • parC mutations are key drivers of reduced susceptibility.
  • Monitoring parC and gyrA mutations aids in predicting fluoroquinolone resistance.

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