Comparative treatment of experimental Staphylococcus aureus endophthalmitis

PURPOSE: To compare treatment strategies for Staphylococcus aureus endophthalmitis, we created an animal model in an aphakic rabbit eye and tested six different approaches to treatment. METHODS: Rabbit eyes were rendered aphakic, and three weeks postoperatively, S. aureus organisms were injected into the vitreous cavity. One group was maintained as a control, Twenty four hours after bacterial injection, six different treatment groups were created for comparison. Clinical inflammation scores, culture results 48 hours after treatment, histopathologic gradings, and development of total corneal opacity three weeks after treatment were assessed. RESULTS: Injection of vancomycin hydrochloride into the vitreous cavity was more effective than injection of cefazolin sodium (P = .01) in reducing the percentage of eyes that had positive culture results and also resulted in lower inflammation scores. Vitrectomy plus injection of either antibiotic was more effective than injection of the same antibiotic alone in reducing culture-positive results and reducing clinical inflammation scores. Addition of systemic corticosteroids to intravitreal antibiotic injection did not improve any measure of outcome. Vitrectomy and injection of intravitreal vancomycin was the most effective strategy to sterilize the vitreous cavity, resulting in the lowest inflammation scores and the smallest percentage of eyes with opaque corneas. CONCLUSION: In an animal model of S. aureus endophthalmitis, the combination of vitrectomy and injection of intraocular vancomycin was the most effective strategy for rapidly controlling the infective process and improving the outcomes measured three weeks after treatment.