Presumed clostridial and aerobic bacterial infections of the cornea in two horses.

Microscopic examination of Gram-stained tissue specimens collected from severe corneal ulcers in 2 horses revealed large gram-positive rods suggestive of Clostridium spp. Clostridium perfringens was isolated from specimens collected from horse 1; anaerobic organisms were not detected in specimens from horse 2. Aerobic bacterial culture revealed Aeromonas hydrophila and Enterobacter cloacae in specimens collected from horses 1 and 2, respectively. An insect exoskeleton was presumed to be the underlying cause of ulceration in horse 1. Cause of ulceration in horse 2 was not determined. Antibiotics used to treat the corneal infections included ticarcillin disodium-clavulanic acid injected one time subconjunctivally and chloramphenicol applied topically at frequent intervals. Horse 2 also received penicillin or trimethoprim-sulfadiazine. Small leukomas were the only lesion remaining between 2 and 7 months after initial evaluation. Chloramphenicol applied topically appears to be an effective treatment against clostridial corneal infections in horses.