Purpose: Besifloxacin is a novel fluoroquinolone antibiotic developed to provide alternative coverage for ocular pathogens with current and emerging in vitro and in vivo resistance to present fluoroquinolones and other commonly dispensed ocular antibiotics. The purpose of this study was to investigate the in vitro efficacy of besifloxacin and 7 comparators against ciprofloxacin- and methicillin-susceptible and nonsusceptible staphylococcal isolates from conjunctivitis, blepharitiis, keratitis, endophthalmitis, and other ocular surface disorders.
Methods: Nonconsecutive ocular Staphylococcus aureus (N=154) and Coagulase-negative Staphylococcus (N=89, including 84 Staphylococcus epidermidis) isolates collected from patients presenting during the 6 years (2003-2008) were evaluated using frozen minimal inhibitory concentration (MIC) panels containing serial dilutions (μg/mL) of besifloxacin (0.004-32), moxifloxacin (0.004-128), ciprofloxacin (0.03-256), azithromycin (0.12-128), oxacillin (0.03-32), gentamicin (0.03-128), trimethoprim (0.5-16), and vancomycin (0.12-32).
Results: Among the fluoroquinolones group, besifloxacin had the lowest MIC90s. MIC90 values (μg/mL) for besifloxacin (4) was 8-fold lower than for moxifloxacin (32) and 32-fold lower than ciprofloxacin (128). Among the nonfluoroquinolone comparators, vancomycin (2) had the lowest MICs followed by gentamicin (16) and trimethoprim (16). Besifloxacin MIC90s (μg/mL) were lowest for isolates recovered from the lacrimal sac (0.25), followed by lids (1), conjunctiva (2), keratitis (4), and intraocular fluids (4).
Conclusions: Due to its improved coverage for ciprofloxacin- and methicillin-resistant staphylococci, besifloxacin may offer extended coverage for some ocular pathogens resistant to current fluoroquinolones recovered from a diverse group of ocular sources. Ninety-five percent of all isolates were covered by a besifloxacin MIC90 of 4 μg/mL.