Intravitreal oxacillin in experimental staphylococcal endophthalmitis.

We compared combined intravitreal and systemic oxacillin to combined subconjunctival and systemic oxacillin in the treatment of experimental staphylococcal endophthalmitis. Intravitreal injection of 500 mcg was nontoxic to all intraocular structures and produced concentrations in the vitreous bactericidal to all susceptible strains of Staphylococcus aureus for almost 24 hours. In eyes treated 8, 10, and 12 hours after intravitreal inoculation of 10000 to 20000 penicillinase-producing S. aureus organisms, intravitreal injection of 500 mcg of oxacillin was superior to subconjunctival injection of 100 mg when each was combined with seven days of intensive intramuscular oxacillin.