Quinolones in collagen shields to treat aminoglycoside-resistant pseudomonal keratitis.

Rabbit corneas were infected with a tobramycin-resistant (minimum inhibitory concentration, 31.25 micrograms/ml) strain of Pseudomonas aeruginosa 27853 (10(3) colony-forming units) and were treated 22 hours later with collagen corneal shields hydrated in either 25 mg/ml ciprofloxacin, 40 mg/ml norfloxacin, 40 mg/ml tobramycin, or deionized water. Shields were removed at 26 hours postinfection, and 1 hour later, corneas were harvested for bacterial enumeration. Application of shields hydrated in ciprofloxacin reduced the number of viable bacteria per cornea approximately 4 log units compared with the application of shields containing tobramycin or deionized water (P less than 0.0001). Use of shields hydrated in norfloxacin reduced the number of P. aeruginosa organisms by greater than 2 log units compared with shields containing tobramycin or deionized water (P less than 0.0001). Ciprofloxacin was significantly more effective than norfloxacin in reducing the number of bacteria per cornea (P less than 0.0001). There was no significant difference in the number of bacteria recovered from corneas treated with tobramycin or deionized water (P less than 0.56).