Abstract
Abstract: :
Purpose: To compare the efficacy of several commonly used topical ophthalmic antibiotic preparations in the treatment of Group B Streptococcus (GBS) in a New Zealand white (NZW) rabbit keratits model. Methods: The choice of topical antibiotics investigated was based on in–vitro testing which demonstrated sensitivity of GBS as follows – fortified cephazolin 50mg/ml > moxifloxacin 0.5% > gatifloxacin 0.3% > ciprofloxacin 0.3% > fortified vancomycin 50mg/ml and resistance to sulfacetamide 10% and balanced salt solution (BSS). Fourteen rabbit corneas received intrastromal injections with 1x103 colony–forming units of GBS in 20µl tryptic soy broth. Following an incubation period of 7 hours each rabbit was treated, around the clock, for one week with one of the following topical ophthalmic preparations – moxifloxacin 0.5%, gatifloxacin 0.3%, fortified vancomycin 50mg/ml, fortified cephazolin 50mg/ml, and BSS as a control. The eyes were treated every hour for the first 24 hours, then every 2 hours for the next 4 days, and finally every 6 hours for the remainder of the study. Daily examinations were performed. On day 7 all rabbits were examined under an operating microscope, euthanized and enucleated. One representative eye from each treatment group underwent histologic examination. Results: By day 7 the rabbits treated with fortified cefazolin and moxifloxacin clinically demonstrated near complete resolution of the infection. The rabbits treated with gatifloxacin were improving but still had visible infiltrates. Corneal ulcers and a severe keratitis developed in the rabbits treated with fortified vancomycin. The control rabbits developed hypopyons and severe corneal neovascularization. Overall efficacy appeared to be fortified cephazolin = moxifloxacin > gatifloxacin > fortified vancomycin > BSS. Conclusions: We have developed a working NZW rabbit model for GBS keratitis. Of the antibiotics tested, fortified cefazolin and moxifloxacin (instead of fortified vancomycin) were the most effective for topical treatment of GBS keratitis.
Keywords: antibiotics/antifungals/antiparasitics • bacterial disease