Evaluation of corneal collagen shields as a drug delivery device for the treatment of experimental Pseudomonas keratitis

Abstract

Purpose: To clarify the role of corneal collagen shields as a drug delivery device for the treatment of bacterial keratitis, the authors studied the effectiveness of topical gentamicin treatment, with and without the use of corneal collagen shields, in a rabbit model of Pseudomonas keratitis.

Methods: Forty-eight New Zealand white rabbits were infected by injecting 500 colony-forming units (CFU) of Pseudomonas aeruginosa into the corneal stroma, and treatment was begun 24 hours later. A 13.6 mg/ml solution of gentamicin was topically administered during a 24-hour period. Collagen shields were soaked in gentamicin 13.6 mg/ml for 5 minutes before placing them on the cornea. Corneas were quantitatively cultured 1 hour after the treatment period ended. Six different groups of rabbits were tested, with the results analyzed as the mean log10 of bacterial CFU.

Results: An untreated control group had significantly more bacteria (7.96 +/- 0.74) than any of 5 treatment groups. No difference was found between groups given a loading dose of antibiotic drops at the beginning of treatment, either with (4.90 +/- 2.41) or without (6.25 +/- 0.54) an antibiotic-impregnated collagen shield. A group treated with a collagen shield augmented with gentamicin drops every 3 hours had fewer bacteria (1.52 +/- 1.82) than a group receiving drops alone (4.15 +/- 1.83) (P less than 0.05). However, treatment with a collagen shield supplemented with drops every 3 hours was not as effective as gentamicin drops administered every 30 minutes (no bacterial growth) (P less than 0.05).

Conclusion: These results show that antibiotic-impregnated collagen shields should not replace traditional antibiotic drop therapy as the mainstay of treatment but may be a useful adjunct to treatment with topical antibiotics.