Abstract
Abstract: :
Purpose: To determine the efficacy of a new liposome–encapsulated vancomycin (LEV) in the treatment of an acute experimentally induced Staphylococcus epidermidis endophthalmitis in comparison with a regular aqueous vancomycin formulation. Methods: For the clinical evaluation group, 30 albino rabbits had their right eye infected with intravitreal inoculum of S. epidermidis (1,0 x 107 colony–forming units [CFU]/ 0,1 mL). Twenty–four hours later, group I rabbits (n=10) received an intravitreal dose of LEV (1mg/0,1 mL) in the right eye; others 10 rabbits (group II) aqueous vancomycin (1mg/0,1ml) and the remaining 10 rabbits (group III) were used as controls. The clinical evaluation included penlight examination, indirect ophthalmoscopy, anterior segment and ocular fundus photographies. For the microbiologic study, 27 rabbits were also infected and divided in the same subgroups as described above. Three eyes from each subgroup were daily used to microbiological analysis through quantitative vitreous bacterial cultures until the third day after antibiotic administration. For the LEV half–life study, 18 rabbit’s aqueous humor and vitreous samples were analyzed through high–performance liquid chromatography (HPLC). For the retinal toxicity study, 8 rabbits received an intravitreous injection of LEV and 8 others used as controls. Both groups were evaluated by electroretinography one day before, 24h, 48h, 1 week and 2 weeks after antibiotic injection and the injected group rabbits had their retina used for light and electron microscopy analysis. Results: LEV showed similar clinical effectiveness comparing to aqueous one. But, one, two and three days after injection, microbiological quantitative analysis showed a statiscally significant (p<0.05) reduction in the number of CFU in vitreous samples from Group I rabbits when compared to Group II and Group III rabbits. HPLC analysis showed a longer half–life of LEV compared to its aqueous formulate. No retinal toxicity was evidenced in the LEV group. Conclusions: LEV remained for a longer period in the vitreous cavity and had a better outcome regarding the number of remaining bacterial colonies. Thus, it seems to be a promising drug to reduce the number of antibiotic reinjections in the human endophthalmitis scenario.
Keywords: antibiotics/antifungals/antiparasitics • vitreous • retina