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S. Lee, H. Koh; The Efficacy of Intravitreal Gatifloxacin and Vancomycin in Rabbits With Experimental Staphylococcus Epidermidis Endophthalmitis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4739.
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To determine whether gatifloxacin can be used safely as an intravitreal agent, retinal toxicity and efficacy of intravitreal gatifloxacin was studied in a rabbit model.
In the toxicity study, twenty-five New Zealand white rabbits were divided 5 groups and the right eyes were treated with five intravitreal doses of gatifloxacin (1000, 500, 250, 100, and 50 µg/0.1 mL). The left eyes served as controls and were injected with balanced salt solution (BSS). The treatment effect of 200 µg/0.1 mL of intravitreal gatifloxacin in the experimental S. epidermidis endophthalmitis was compared with that of 1000 µg/0.1 mL of intravitreal vancomycin and intravitreal BSS (untreated control) using 30 rabbits (10 rabbits in each group). Intravitreal antibiotic therapy commenced 24 h after S. epidermidis intravitreal challenge (105 colony forming unit/0.1 mL). Toxicity was evaluated using electroretinography (ERG) and light microscopy 4 weeks after intravitreal injections. The bactericidal efficacy was determined by ERG, clinical grading, histopathologic grading, and bacterial culture of vitreous aspirates.
ERG and morphometric results of five intravitreal doses of gatifloxacin were statistically equivalent to rabbits given intravitreal BSS. In the efficacy study, eyes treated with gatifloxacin and vancomycin had a significantly better appearance clinically and histologically than untreated control eyes. When compared to antibiotic treated eyes, untreated control eyes had a significant reduction in b-wave amplitude ratio. Eyes in the gatifloxacin group showed similar appearance to those in the vancomycin treated group clinically, histologically, and functionally as proved with ERG. All aspirates from the antibiotic treated groups were culture-negative 5 days after bacterial inoculation, whereas all eyes in the untreated control group were culture-positive. Only one of five eyes in the untreated control group was culture-negative by 7 days after inoculation.
Intravitreal gatifloxacin in doses up to 1000 µg/0.1 mL caused no ERG or retinal histologic abnormality. Furthermore, this study demonstrated that intravitreal injection of 200 µg /0.1mL gatifloxacin seems to be equally effective with intravitreal 1000 µg /0.1 mL vancomycin in the treatment of S. epidermidis endophthalmitis. If proven safe and efficacious by further study in humans, intravitreal injection of gatifloxacin could be considered as an alternative to vancomycin.
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