Clinical and bacteriological outcome of combined intravitreal injection of vancomycin and ceftazidime in experimentally induced endophthalmitis

Abstract

Introduction Endophthalmitis, despite being rare, is the most serious complication of ocular surgery. Aminoglycosides, used in combination with vancomycin (VAN), were found to cause macular toxicity. Ceftazidime has been suggested as an alternative antibiotic because of its lower risk of retinal toxicity. Purpose of the study The purpose is to evaluate outcome of intravitreal injection (IVI) of VAN and ceftazidime combination versus ciprofloxacin on experimentally induced endophthalmitis. Materials and methods Twenty-one albino rabbits were divided into three groups as follows: group I received IVI of 0.1 ml saline, group II received IVI of VAN (1 mg/0.1 ml) and ceftazidime (2.25 mg/0.1 ml), and group III received IVI of ciprofloxacin (1 mg/0.1 ml). Right eyes were inoculated with 10 5 colony forming units (CFU)/0.l ml of Staphylococcus epidermidis . After 24 h, inoculated eyes were examined by indirect ophthalmoscopy for signs and severity of endophthalmitis according to the modified scheme of Peyman and Bassili, and IVI was provided. On day 3 of the study, inoculated eyes were re-examined clinically, vitreous samples were obtained for bacteriological examination, and if culture was positive, antibiotics were reinjected. On day 6, animals were killed, right eyes were enucleated, and contents of the posterior segment were inoculated on blood agar for evaluation of bacterial growth and counting the CFU. Results On day 3, frequency of animals having severe grades of conjunctival injection and corneal edema was significantly higher in groups I and III compared with group II, and not significantly higher in group I compared with group III. Frequency of animals showing good red reflex was significantly higher in group II compared with groups I and III, and not significant different in group III compared with group I. On day 3, the mean number of CFU was significantly lower in group II compared with groups I and III with significantly lower number in group III compared with group I. On day 6, all samples of group II were sterile, while mean number of CFU was significantly lower in group III compared with group III. Conclusion Combined therapy using VAN and ceftazidime provided proper clinical and bacteriological control of experimentally induced endophthalmitis, with significant difference from single-drug therapy.