INFECTIOUS CRYSTALLINE KERATOPATHY - THE ROLE OF BACTERIAL EXOPOLYSACCHARIDE

Objectives.-Infectious crystalline keratopathy is a unique pauci-inflammatory infection of the cornea most commonly due to viridans type streptococci. We investigated the hypothesis that production of exopolysaccharide by streptococci, a property that can be induced by growth conditions, may contribute to the pathogenesis of infectious crystalline keratopathy by suppressing the ocular immune response. Methods.-Streptococcus sanguis type II was grown under two conditions, conventionally in brain-heart infusion broth and in 5% sucrose-supplemented brain-heart infusion broth, to promote exopolysaccharide formation. Rabbit corneas were inoculated by passage of 9-0 silk sutures soaked in bacterial suspensions. Results.-Arborizing, sharply demarcated pauci-inflammatory lesions were noted in 71% of rabbit corneas inoculated with S sanguis type II grown in sucrose-supplemented media and in 25% of control corneas (P=.05). Suppurative lesions developed in the remaining corneas. Histologic evaluation of infectious crystalline keratopathy lesions revealed characteristic features. Conclusion.-Increased exopolysaccharide formation by S sanguis type II is associated with production of infectious corneal lesions that resemble those of infectious crystalline keratopathy.