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Quinolones in collagen shields to treat aminoglycoside-resistant pseudomonal keratitis
J A Hobden1, J J Reidy, R J O'Callaghan
1Department of Microbiology, Louisiana State University Medical Center School of Medicine, New Orleans.
Abstract:
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).
Insights
Ciprofloxacin-soaked corneal shields significantly reduced Pseudomonas aeruginosa in rabbit eyes, offering a promising treatment for resistant bacterial keratitis. Norfloxacin showed moderate effectiveness, while tobramycin provided no benefit against this resistant strain.
Area of Science:
- Ophthalmology
- Microbiology
- Pharmacology
Background:
- Pseudomonas aeruginosa is a common cause of bacterial keratitis.
- Antibiotic resistance in P. aeruginosa poses a significant clinical challenge.
- Topical antibiotic delivery via corneal shields is an alternative treatment strategy.
Purpose of the Study:
- To evaluate the efficacy of ciprofloxacin, norfloxacin, and tobramycin delivered via collagen corneal shields against a tobramycin-resistant P. aeruginosa strain in a rabbit keratitis model.
Main Methods:
- Rabbit corneas were infected with P. aeruginosa.
- Corneal shields hydrated with ciprofloxacin, norfloxacin, tobramycin, or deionized water were applied.
- Bacterial counts were enumerated from harvested corneas post-treatment.
Main Results:
- Ciprofloxacin shields reduced bacterial load by approximately 4 log units compared to controls (P < 0.0001).
- Norfloxacin shields reduced bacterial load by over 2 log units compared to controls (P < 0.0001).
- Ciprofloxacin was significantly more effective than norfloxacin (P < 0.0001); tobramycin showed no significant difference from controls (P < 0.56).
Conclusions:
- Ciprofloxacin-delivered corneal shields are highly effective against tobramycin-resistant P. aeruginosa keratitis.
- Norfloxacin offers moderate efficacy, while tobramycin is ineffective in this model.
- Corneal shields represent a viable drug delivery system for managing resistant bacterial eye infections.