The Efficacy of Intravitreal Vancomycin and Dexamethasone in the Treatment of Experimental Bacillus cereus Endophthalmitis

Abstract

Purpose: Bacillus cereus causes the most virulent and refractoryform of endophthalmitis. The authors analyzed effectiveness of intravitrealvancomycin with or without dexamethasone for experimental Bacillus cereus endophthalmitis. Methods: Rabbit eyes were injected intravitreally with 1 x 106colony-forming units of Bacillus cereus organisms. At 24 hours after injection,eyes were injected intravitreally with 0.1 ml of balanced salt solution (group 1,n = 10), 1 mg vancomycin (group 2, n = 10), and antibiotic plus 0.4 mg dexamethasone(group 3, n = 10). Inflammatory scores were assessed 7 days and 14days after treatment. Furthermore, histologic grading was carried out at the conclusionof the clinical observations. Results: Eyes treated with vancomycin, withor without dexamethasone at 7 days and 14 days expressed significant less inflammationover iris and vitreous than the control group (p < 0.05). Moreover,eyes treated with vancomycin with dexamethasone showed less inflammationover the conjunctiva and vitreous at 7 days and over the iris and vitreous at14 days, compared to antibiotic treatment alone (p < 0.05). Additionally, at14 days, the histopathological changes of eyes treated with vancomycin withdexamethasone had less conjunctival inflammation, mild iridocyclitis, less vitreouscells, and less choroidal vasculitis and retinitis compared to control groupand antibiotic treatment alone, respectively (pp < 0.05). Conclusion: Intravitrealinjection of vancomycin improved the therapeutic outcome of Bacillus cereusendophthalmitis. The addition of dexamethasone to antibiotic treatment provideda therapeutic benefit over antibiotic alone.