Collagen shields containing tobramycin for sustained therapy (24 hours) of experimental Pseudomonas keratitis.

We compared collagen shields hydrated in 1.36% tobramycin with topical 1.36% tobramycin for sustained treatment of experimental Pseudomonas keratitis in rabbits. Antibiotic therapy for a total of 24 hours was initiated 14 hours after an intrastromal injection of 10(3) logarithmic phase Pseudomonas aeruginosa. Seven groups were treated as follows: groups 1-3, collagen shields hydrated in tobramycin supplemented with topical 1.36% tobramycin drops at 4, 6, or 8 hour intervals; group 4, collagen shields hydrated in tobramycin without any further topical supplementation; group 5, topical tobramycin therapy, initially every half-hour for 4 hours, then hourly; group 6, collagen shields hydrated in balanced saline solution; and group 7, no treatment. Each group contained four eyes. The groups treated with collagen shields supplemented every 4 or 6 hours with topical tobramycin had significantly fewer colony forming units (CFU) than those receiving topical or collagen shield therapy alone (P < 0.001). The group treated with collagen shields hydrated in sterile saline had 10(7) CFU per cornea, which was not significantly different from the untreated group (P > 0.2). Collagen shields hydrated in tobramycin and supplemented with topical tobramycin were effective in sustained treatment of experimental Pseudomonas keratitis.