Correlation of Phenotype and Its Corneal Virulence.

Purpose: is an ocular pathogen and a leading cause of keratitis. It produces hemolysins and at least 3 proteases. The purpose of the present study is to compare the secretion of hemolysins and proteases between 28 ocular isolates and one non-ocular strain and to determine their relationship to ocular virulence in selected strains using a rabbit model of infection.

Materials And Methods: Culture supernatants were compared for protease production and hemolysis. Selected strains were injected into rabbit corneas and their virulence and pathology recorded. The major protease activity in a virulent strain was identified and the gene was cloned and expressed as a recombinant protein. The corneal toxicity of this protease was determined. Antibodies to the native protease were generated and tested for neutralizing activity and . The corneal pathology of the protease was compared to the pathology of V8 protease.

Results: Strains that exhibited the least protease activity caused significantly less ocular pathology (p ≤ 0.003). Strains that were hemolytic and secreted a major protease had numerically higher SLE scores. This protease was identified as the serine protease Esp. The recombinant Esp protease caused extensive pathology when injected into the corneal stroma (7.62 ± 0.33). Antibody generated against native Esp did not neutralize the activity of the protease or . The antibody reacted with Esp proteases secreted by other strains. Esp protease and its homologue in caused similar ocular pathology when injected in the rabbit corneal stroma.

Conclusion: Hemolysins and proteases seem to be important in corneal pathology caused by infections. The Esp protease mediates significant corneal damage. Esp and V8 protease caused similar and extensive edema in rabbit corneas.