Effects of zinc sulfate on Pseudomonas aeruginosa infections and protease in rabbit corneas.

Zinc ions were shown to reversibly inhibit the activity of Pseudomonas protease. Zinc sulfate was more effective topically in preventing corneal perforations by this enzyme than either cysteine or edetate disodium (Na2 EDTA). The reversibility of the enzyme inactivation by zinc sulfate and its efficacy in preventing perforations were used to estimate the duration of the enzyme activity in the cornea. The protease was found to retain its activity in the rabbit cornea for up to two days after intrastromal injection. The extent of corneal destruction in rabbit corneas infected with live Pseudomonas cells was significantly greater in eyes treated with zinc sulfate than in controls, precluding its use in a clinical setting.