Intravitreal tigecycline treatment in experimental Acinetobacter baumannii endophthalmitis

To investigate the clinical and microbiological effectivity of intravitreal tigecycline in an experimental rabbit endophthalmitis model caused by imipenem resistant Acinetobacter baumannii.

Forty-eight eyes of 24 New Zealand white albino rabbits were divided into six groups (n=8 in each). The right eyes were divided into three groups and defined as infected group; left eyes were divided into three groups and defined as uninfected group. Infected group received 0.1 ml intravitreal A. baumannii suspension. Twenty-four hours after bacterial inoculation, group 1 received 1 mg/0.1 ml tigecycline and group 2 received 0.5 mg/0.1 ml tigecycline. Group 3 eyes received no treatment. In group 4, 0.1 ml of saline solution was injected. Groups 5 and 6 were received intravitreal tigecycline injection of 1 mg/0.1 ml and 0.5 mg/0.1 ml respectively. The eyes were enucleated for histopathological evaluation on the sixth day. Clinical and histological scoring systems were used to evaluate clinical and histological severity of the intraocular infection.

The mean clinical scores of the six groups at the sixth day were 11±1.92, 12.4±6.2, 8.5±2.7, 0, 3±1.3, and 3±1.4 respectively. Mean histopathological scores were 7.8±2.8, 7.0±1.5, 5.6±1.4, 0, 0, and 0 respectively. There was no significant difference in mean clinical and histopathological scores of infected group (groups 1, 2 and 3). There was significant difference in mean clinical scores of groups 5 and 6 compared with group 4. Groups 4, 5 and 6 showed normal histological structure in histopathological evaluation and showed no significant difference. Microbiological cure was achieved in all infected eyes.

Experimental rabbit endophthalmitis model caused by imipenem resistant A. baumannii was microbiologically cured by intravitreal tigecycline injection. However, a hypersensitivity-like reaction due to intravitreal application of tigecycline limits the use of this antimicrobial agent in A. baumannii endophthalmitis.