EFFICACY OF TOBRAMYCIN DROPS APPLIED TO COLLAGEN SHIELDS FOR EXPERIMENTAL STAPHYLOCOCCAL KERATITIS

Treatment of staphylococcal keratitis includes tobramycin drops at rep eated intervals, a prolonged therapy that is disruptive to the patient . To identify a regimen involving less frequent drug application, we c ompared the efficacy of fortified tobramycin (1.36%) administered by c ollagen shields or in topical drop form to rabbit corneas intrastromal ly infected with staphylococci. Eyes were treated with shields hydrate d in and supplemented with fortified tobramycin drops (1.36%) applied every 1, 2, 5, or 10 h, from 10 to 20 h postinfection. For topical dro p treatment alone, tobramycin was applied following the identical regi men. Untreated corneas contained 10(6) colony forming units. Shields s upplemented with tobramycin drops applied every 1, 2, or 5 h sterilize d 100% of the corneas. Shields supplemented with tobramycin drops appl ied at 10 h sterilized 58% of the corneas. Topical delivery of tobramy cin every h sterilized all corneas; drops alone applied at longer inte rvals, such as 2, 5, or 10 h, sterilized 83%, 17%, and 0% of the corne as, respectively. Collagen shield delivery of tobramycin with suppleme ntal topical drops can eradicate staphylococci in this model with less frequent dosing intervals than are required with topical therapy alon e.