Antibacterial efficacy of prophylactic besifloxacin 0.6% and moxifloxacin 0.5% in patients undergoing cataract surgery

BACKGROUND: The purpose of this study was to investigate the ocular bacterial flora in patients scheduled to undergo cataract surgery and compare the antibacterial effects of besifloxacin ophthalmic suspension 0.6% and moxifloxacin ophthalmic solution 0.5% in these patients. METHODS: This was a prospective, randomized, laboratory-masked clinical trial. Patients received besifloxacin or moxifloxacin “quater in die” or QID (four times a day) for 3 days before cataract surgery in the surgical eye and 1 hour before surgery in the nonsurgical fellow eye. Conjunctival and eyelid swabs were obtained from both eyes at baseline and after treatment, on the day of surgery (Visit 2). Swabs were processed for bacterial colony counts (in terms of colony-forming units) and species identification. In vitro antibiotic susceptibilities of isolates were determined using Clinical and Laboratory Standards Institute breakpoints. RESULTS: Fifty-nine patients (n=28 besifloxacin, n=31 moxifloxacin) completed the study. The majority (73%) of conjunctival samples were culture negative at baseline. The most frequent isolates were coagulase-negative staphylococci (CoNS, 89%), specifically Staphylococcus epidermidis (72%). Both fluoroquinolones reduced the lid CFU values when administered QID for 3 days (P≤0.019), but only besifloxacin reduced the lid CFU estimate 1 hour following instillation of a single drop (P=0.039). Fewer besifloxacin-treated eyes had lids that were culture positive for CoNS at Visit 2 compared with moxifloxacin-treated eyes regardless of dosing regimen (P≤0.03). The minimum inhibitory concentration (MIC(90)) of besifloxacin against methicillin-resistant S. epidermidis (MRSE) was eightfold lower than that of moxifloxacin. CONCLUSION: Besifloxacin appeared more effective in reducing bacterial counts on eyelids of patients undergoing cataract surgery, with significant reductions as early as 1 hour postdose, compared with moxifloxacin. Besifloxacin was more active in vitro against MRSE.