March 1998
Volume 39, Issue 3
Free
Articles  |   March 1998
Pseudomonas aeruginosa protease IV produces corneal damage and contributes to bacterial virulence.
Author Affiliations
  • L S Engel
    Department of Microbiology, Immunology, and Parasitology, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA.
  • J M Hill
    Department of Microbiology, Immunology, and Parasitology, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA.
  • J M Moreau
    Department of Microbiology, Immunology, and Parasitology, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA.
  • L C Green
    Department of Microbiology, Immunology, and Parasitology, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA.
  • J A Hobden
    Department of Microbiology, Immunology, and Parasitology, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA.
  • R J O'Callaghan
    Department of Microbiology, Immunology, and Parasitology, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA.
Investigative Ophthalmology & Visual Science March 1998, Vol.39, 662-665. doi:
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      L S Engel, J M Hill, J M Moreau, L C Green, J A Hobden, R J O'Callaghan; Pseudomonas aeruginosa protease IV produces corneal damage and contributes to bacterial virulence.. Invest. Ophthalmol. Vis. Sci. 1998;39(3):662-665.

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Abstract

PURPOSE: A Pseudomonas mutant deficient in protease IV has significantly reduced virulence in experimental keratitis. In the present study, the corneal toxicity of purified protease IV and its ability to augment the virulence of protease-IV-deficient bacteria were analyzed. METHODS: The toxicity of purified protease IV was determined by intrastromally injecting the exoenzyme (20-200 ng) into the cornea. The effects of protease IV on the corneal virulence of the protease-IV-deficient strain, PA103-29::Tn9, were determined by injecting eyes with 1000 CFU of log phase bacteria plus either 200 ng active purified protease IV or 200 ng heat-inactivated protease IV. Changes in ocular disease, determined by slit-lamp examination, were measured at 3, 16, 22, and 27 hours after infection. Colony-forming units per cornea were quantified at 27 hours after infection. RESULTS: Purified protease IV at doses from 50 to 200 ng induced epithelial defects within 3 hours of injection. Injection of 20 ng active protease IV or heat-inactivated protease IV (200 ng) had no effect on ocular tissue. Corneal virulence of the protease-IV-deficient strain was augmented by intrastromal injection with purified protease IV but not with heat-inactivated protease IV (P < or = 0.0001). Neither active nor heat-inactivated protease IV altered the growth of bacteria in the cornea (6 log units; P = 0.81). CONCLUSIONS: The important role of protease IV in corneal virulence was demonstrated by direct toxicity and by its ability to significantly augment the virulence of protease-IV-deficient Pseudomonas.

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