Prevalence of low-level and high-level resistance to fluoroquinolones in Streptococcus pneumoniae in Getafe, Spain
Abstract number: P1746
García-Cañas A., García-Hierro P., Soria T., Pérez-Millán F.J., Alós J.I.
Fluoroquinolone (FQ) resistance among strains of Streptococcus pneumoniae has emerged worlwide. Strains with high-level resistance and even with low-level resistance (first-step mutants) have been associated with treatment failures.
Objectives: The aim of this study was to assess the prevalence of low-level and high-level resistance to fluoroquinolones in Streptococcus pneumoniae strains of Getafe, Spain.
Methods: A total of 100 S. pneumoniae strains (28 from children and 72 from adults) were isolated from clinical samples between November 2006 and June 2007 at the Department of Clinical Microbiology of Getafe University Hospital. The main sources of the isolates were blood samples (42%), conjunctival exudates (17%), and respiratory samples (37%).
Susceptibility to 5 FQ (levofloxacin, norfloxacin, pefloxacin, ciprofloxacin, and sparfloxacin) was performed using disk diffusion method. The results were interpreted following the phenotypic test designed for Varon et al. (Antimicrob Agents Chemother 2006;50:5729) for the detection of the low- and high-level FQ-resistant mutants according to the inhibition zone diameters of the 5 FQ.
We also performed the broth microdilution method to determine the susceptibility to levofloxacin.
Results: 4 of the isolates showed resistance to levofloxacin (high-level resistant mutants) and 96 were susceptible by the broth microdilution method and CLSI guidelines. Using the FQ disks and the interpretations of Varon et al. 60 strains had the wild phenotype (susceptible), 5 strains had an increased efflux and the rest harboured a phenotype compatible with topoisomerase IV (28 strains) or gyrase (3 strains) mutations.
Conclusions: The results of the study showed that 34.5% of the strains susceptible to levofloxacin by the CLSI had a low-level resistance to this antibiotic and so the potencial to generate high level resistant mutants.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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