Effectiveness of mupirocin and polymyxin B in experimental Staphylococcus aureus, Pseudomonas aeruginosa, and Serratia marcescens keratitis.

PURPOSE: The purpose of this study was to determine the effectiveness of mupirocin and polymyxin B, alone and in combination, in vitro and in vivo using rabbit models of, and keratitis. METHODS: Rabbit eyes were intrastromally injected with 1,000 colony-forming units (CFUs) of or or 100 CFUs of Rabbits were then treated with 2.7 mg/mL mupirocin, 10,000 U/mL polymyxin B, a mupirocin:polymyxin B combination, or 0.3% ciprofloxacin. Vehicle and untreated controls were also included. Treatment schedules depended on the strain injected. The number of CFUs was determined for all eyes after treatment. RESULTS: The mupirocin:polymyxin B combination was effective for all three genera both in vitro and in vivo. For keratitis, the mupirocin:polymyxin B combination was more effective than either drug alone and significantly reduced the log number of bacteria in the cornea by more than 3 logs compared with the vehicle or untreated controls (p