Fluoroquinolone susceptibilities to methicillin-resistant and susceptible coagulase-negative Staphylococcus isolated from eye infection

Abstract

Purpose: To evaluate the fluoroquinolone susceptibilities of ocular isolate coagulase-negative staphylococci (CoNS), identified at the Microbiology Laboratory - UNIFESP. Design: Experimental laboratory investigation. Methods: The minimum inhibitory concentrations (MICs) of 21 strains of methicillin-resistant coagulase-negative staphylococci (MRCoNS) and 22 methicillin-sensitive coagulase-negative staphylococci (MSCoNS) to ciprofloxacin, ofloxacin, gatifloxacin and moxifloxacin were determined, using the E-test method standardized by the Clinical and Laboratory Standards Institute (CLSI/NCCLS). Results: The MIC90s (μg/ml) for the second generation of tested fluoroquinolones were higher than the fourth generation, especially for the methicillin-resistant coagulase-negative staphylococci group. Conclusion: Our results indicate that methicillin-sensitive coagulase-negative staphylococci are more susceptible to quinolones than are methicillin-resistant coagulase-negative staphylococci and that fourth generation fluoroquinolones appear to be more potent, affecting even coagulase-negative staphylococcal strains resistant to second generation fluoroquinolones.