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Characterisation of fluoroquinolone-resistant clinical isolates of Streptococcus pyogenes in Barcelona, Spain

A Rivera1, M Rebollo, F Sánchez

  • 1Servei de Microbiologia, Hospital de la Santa Creu i Sant Pau, and Unitat de Microbiologia, Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Barcelona, Spain.

Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases
|August 18, 2005
PubMed

Insights

Mechanisms of ciprofloxacin resistance in Streptococcus pyogenes involve mutations in ParC and GyrA proteins. These genetic changes correlate with reduced susceptibility and define distinct bacterial clonal groups.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Streptococcus pyogenes is a significant human pathogen.
  • Understanding antibiotic resistance mechanisms is crucial for effective treatment.
  • Quinolone resistance in S. pyogenes is an emerging concern.

Purpose of the Study:

  • To investigate the molecular basis of ciprofloxacin resistance in Streptococcus pyogenes.
  • To determine the clonal relationships among resistant isolates.

Main Methods:

  • Susceptibility testing for ciprofloxacin and levofloxacin.
  • Sequencing of quinolone resistance-determining regions (QRDRs) in ParC and GyrA.
  • emm typing for clonal analysis.

Main Results:

  • Four isolates showed reduced susceptibility due to specific ParC mutations (Ser80Pro, Ser79Ala, Ser79Phe/Ala121Val).
  • Two isolates exhibited high-level resistance with combined ParC and GyrA mutations (Ser79Phe/Ala121Val and Ser81Tyr).
  • emm typing and QRDR sequencing identified two distinct clusters of resistant isolates.

Conclusions:

  • Mutations in ParC and GyrA are key mechanisms conferring quinolone resistance in S. pyogenes.
  • Specific mutation profiles correlate with resistance levels and can be used for molecular epidemiology.
  • The findings highlight the need for monitoring quinolone resistance in S. pyogenes.

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