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B.J. Wiskur, M.L. Robinson, A.J. Reed, B.D. Novosad, M.C. Callegan; Improved Antibiotic Therapy for Bacillus cereus Endophthalmitis . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1898.
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To measure the therapeutic effectiveness of gatifloxacin or vancomycin combined with dexamethasone sodium phosphate in a Bacillus cereus endophthalmitis model.
New Zealand White rabbits were injected with 100 colony forming units (CFU) of Bacillus cereus in the posterior chamber of the eye. Following infection, rabbits received gatifloxacin (3mg/mL) alone, vancomycin (10 mg/mL) alone, dexamethasone (1mg/mL) + gatifloxacin or vancomycin, or PBS alone. Treatment regimens included intravitreal injection of drug at 2, 4, or 6 hrs post–infection (PI). Retinal function was evaluated every 2 hrs after treatment until 8 hrs PI. A– and B–wave function were monitored by electroretinography (ERG) throughout the course of infection to evaluate retinal function. Bacteria present in the posterior chamber were quantified by plating triplicate 10–fold serial dilutions of vitreous onto BHI agar.
Overall, vancomycin treatment resulted in better retention of both A– and B–waves when compared to all other treatment groups. Rabbits treated at 2 hrs PI with gatifloxacin or vancomycin + dexamethasone maintained a significantly higher A– and B–wave amplitude at 8 hrs PI and a significantly higher B–wave amplitude at both 6 and 8 hrs PI compared to the dexamethasone only or PBS treated groups. With the exception of the PBS control, dexamethasone alone, and vancomycin + dexamethasone groups at 6 hrs PI, all treatment groups completely sterilized the eyes.
The results demonstrate the effectiveness of early intravitreal injection of antibiotics in treating Bacillus cereus endophthalmitis and improvement in therapeutic outcome by combination of vancomycin with dexamethasone. Delay in treatment past 6 hrs PI significantly reduced ERG retention.
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