A partial-thickness epithelial defect increases the adherence of Pseudomonas aeruginosa to the cornea

Some patients with infectious keratitis have no clinically demonstrable corneal abrasion predisposing them to infection. Subtle, undetectable corneal injuries may facilitate bacterial adherence to the cornea, eventually leading to keratitis. To study this concept, we have developed a rabbit model in which a partial-thickness corneal epithelial defect was induced by filter paper impression on the cornea that removed one to two layers of corneal epithelium. Following this injury, the corneas were incubated with Pseudomonas aeruginosa, washed, and the number of bacteria adhering to the injured corneas as well as to control corneas was quantitated. Corneas treated with filter paper, either ex vivo or in vivo, allowed 20 times more bacteria to adhere than did the untreated control corneas (P<0.01). This superficial epithelial defect increased Pseudomonas adherence to the cornea for up to 72 hr after injury. When corneal injury was extended to the stroma, the adherence of Pseudomonas was further augmented as compared to adherence to the superficially injured cornea. Thus, we conclude that a clinically subtle, partial-thickness corneal epithelial injury can markedly facilitate the adherence of Pseudomonas aeruginosa, which may be an important predisposing factor for infectious keratitis.