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Changes in fluoroquinolone-resistant Streptococcus pneumoniae after 7-valent conjugate vaccination, Spain

Adela G de la Campa1, Carmen Ardanuy, Luz Balsalobre

  • 1Instituto de Salud Carlos III, Madrid, Spain.

Emerging Infectious Diseases
|June 16, 2009
PubMed

Insights

Ciprofloxacin resistance in Streptococcus pneumoniae remains stable in Spain. Most resistance is due to gyrase and topoisomerase IV mutations, with specific clones dominating resistant strains.

Area of Science:

  • Microbiology
  • Antimicrobial Resistance
  • Molecular Epidemiology

Background:

  • Streptococcus pneumoniae is a leading cause of bacterial infections worldwide.
  • Antibiotic resistance in S. pneumoniae is a growing public health concern.
  • Ciprofloxacin is a fluoroquinolone antibiotic used to treat S. pneumoniae infections.

Purpose of the Study:

  • To determine the prevalence and mechanisms of ciprofloxacin resistance in S. pneumoniae isolates from Spain in 2006.
  • To compare resistance patterns with previous findings from 2002.
  • To identify the genetic determinants and clonal types associated with resistance.

Main Methods:

  • Antimicrobial susceptibility testing of 4,215 S. pneumoniae isolates.
  • Determination of minimum inhibitory concentrations (MICs) for ciprofloxacin.
  • Analysis of mutations in topoisomerase IV (parC, parE) and gyrase (gyrA) genes.
  • Investigation of efflux pump activity using reserpine.
  • Genotyping of isolates to identify clonal lineages.

Main Results:

  • Overall ciprofloxacin resistance was 2.3% (98/4,215 isolates).
  • Low-level resistance was associated with efflux or single topoisomerase IV mutations.
  • High-level resistance involved mutations in gyrA and parC/parE.
  • New mutations in parC (S80P) and gyrA (S81V, E85G) were identified.
  • Two major clones (Spain9V-ST156 and Sweden15A-ST63) accounted for 34.7% of resistant isolates.
  • Changes in the prevalence of other clones and emergence of new genotypes were observed.

Conclusions:

  • Ciprofloxacin resistance in S. pneumoniae in Spain remained stable between 2002 and 2006.
  • Mutations in gyrase and topoisomerase IV are key mechanisms of resistance.
  • Specific clones play a significant role in the dissemination of resistant strains.
  • Continued surveillance is necessary to monitor resistance trends and emerging genotypes.

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