The corneal response to Pseudomonas aeruginosa: histopathological and enzymatic characterization.

The host response to the intrastromal injection of heat-inactivated Pseudomonas aeruginosa cells was studied. An extensive polymorphonuclear leukocyte (PMN) infiltration, which progressed to ulceration within 1 week, was observed. In some cases descemetoceles also developed. Only a limited degree of PMN infiltration and no ulcerations were observed at 1 week in eyes treated with corticosteroids. Collagenase and proteolytic enzymes capable of degrading proteoglycans were found in the ulcerated corneas. A correlation was made between the level of these host-derived enzymes and the extent of corneal destruction. It was concluded that corneal destruction by P. aeruginosa depends not only on the Pseudomonas protease, which rapidly destroys the cornea, but also on host-derived enzymes which are capable of degrading both collagen and proteoglycans.