Abstract
Purpose: :
To determine in vitro activity of besifloxacin, a new generation fluoroquinolone, as compared to vancomycin, moxifloxacin and ciprofloxacin against Staphylococcus epidermidis isolates.
Methods: :
Forty-two S. epidermidis isolates from vitreous (30), anterior chamber (4) and surface disease (8) recovered during the last four years (2005-2008) were chosen at random and reconstituted from the Bascom Palmer Eye Institute microbiology pathogen bank. Of these, 18 were methicillin resistant (MRSE), 22 moxifloxacin resistant and 25 ciprofloxacin resistant. Frozen minimum inhibitory concentration (MIC) panels prepared by TREK Diagnostics containing serial dilutions of besifloxacin, moxifloxacin, ciprofloxacin, and vancomycin were used in evaluation. Minimum bactericidal concentrations (MBC) were also determined and 90th percentile values were calculated for MIC and MBC (MIC90, MBC90).
Results: :
In vitro results were (MIC90 ug/mL, % sensitive) vancomycin (2, 100%), besifloxacin (4, no breakpoints, 59.1% < 1 ug/ml), moxifloxacin (64, 40.4%) and ciprofloxacin (64, 38.1%). MBC90 was calculated for 67% of the isolates and results were: vancomycin (2), besifloxacin (4), moxifloxacin (128) and ciprofloxacin (256). No significant difference in MIC90 (ug/ml) was observed for MSSE versus MRSE isolates: vancomycin: 2/2, besifloxacin: 2/4, moxifloxacin: 32/64, and ciprofloxacin: 64/64.
Conclusions: :
The MIC90 for besifloxacin against these randomly selected S. epidermidis isolates was significantly lower than moxifloxacin and ciprofloxacin. The MBC90 was also much lower for besifloxacin than the prior generation fluoroquinolones. Besifloxacin may provide coverage for some ciprofloxacin and moxifloxacin resistant S. epidermidis isolates.
Keywords: antibiotics/antifungals/antiparasitics • Staphylococcus