Comparative efficacy of topical moxifloxacin versus ciprofloxacin and vancomycin in the treatment of P-aeruginoso and ciprofloxacin-resistant MRSA keratitis in rabbits

Purpose: To evaluate the in vivo efficacy of topical moxifloxacin 0.5% versus ciprofloxacin 0.3% in the treatment of Pseudomonas aeruginosa keratitis and topical moxifloxacin 0.5% versus vancomycin 50 mg/mL in the treatment of ciprofloxacin-resistant, methicillin-resistant Staphylococcus aureus (MRSA) keratitis in rabbits. Methods: Experimental bacterial keratitis was induced in rabbits by corneal intrastromal injection. Infection proceeded for 12 hours, after which topical antibiotics were applied hourly for 12 hours. Corneal homogenates were plated with serial dilutions for quantitative bacteriology. Results: Both moxifloxacin and ciprofloxacin performed significantly better than control in the treatment of Pseudomonas aeruginosa keratitis (P = 0.0046 and 0.0069, respectively); there were no significant differences between these 2 drugs in bactericidal activity (P = 0.1120). Moxifloxacin performed significantly better than control in the treatment of ciprofloxacin-resistant MRSA (P = 0.0321) keratitis, and vancomycin showed a trend toward statistical significance in performing better than control (P = 0.0576); there were no significant differences between these 2 drugs in bactericidal activity (P = 0.5205). Conclusions: Topical moxifloxacin 0.5% and ciprofloxacin 0.3% have similar efficacy in the treatment of Pseudomonas aeruginosa keratitis in rabbits. Topical moxifloxacin 0.5% and vancomycin 50 mg/mL have similar efficacy in the treatment of ciprofloxacin-resistant MRSA keratitis in rabbits. These results suggest a potential value for topical moxifloxacin as a broad-spectrum agent in the treatment of bacterial keratitis.