Intracameral antibiotic agents for endophthalmitis prophylaxis

PURPOSE: To assess in vitro whether intracameral antibiotic agents are plausibly effective prophylaxis against Staphylococcus aureus endophthalmitis. SETTING: University research laboratory.Staphylococcus aureus was cultured for 8 hours with vancomycin (50 microg/mL) or piperacillin/tazobactam (512/64 microg/mL). Without reducing the bacterial counts, the antibiotic concentration was halved every 2 hours to simulate the half-life of antibiotic agents in the anterior chamber. The number of colony forming units (CFU)/mL was measured at 0, 2, 4, 6, and 8 hours. RESULTS: Vancomycin inhibited the growth of methicillin-resistant S aureus such that the CFU/mL was 1000 times higher in the control group after 8 hours. Piperacillin/tazobactam nearly eliminated 1 oxacillin-susceptible strain and reduced the CFU/mL of another strain 1000-fold. CONCLUSIONS: Intracameral vancomycin may inhibit the growth of S aureus in the anterior chamber after surgery. Inhibiting the growth could increase the chances that the eye's innate defenses would eliminate the bacterial contamination that could cause endophthalmitis.