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The corneal response to Pseudomonas aeruginosa: histopathological and enzymatic characterization
Abstract:
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.
Insights
Pseudomonas aeruginosa infection causes severe corneal destruction via bacterial proteases and host-derived enzymes. Corticosteroid treatment limited polymorphonuclear leukocyte infiltration and prevented ulceration in this study.
Area of Science:
- Ophthalmology
- Microbiology
- Immunology
Background:
- Pseudomonas aeruginosa is a significant cause of bacterial keratitis.
- Bacterial keratitis can lead to severe corneal damage and vision loss.
Purpose of the Study:
- To investigate the host response to Pseudomonas aeruginosa keratitis.
- To identify the enzymes involved in corneal destruction.
Main Methods:
- Intrastromal injection of heat-inactivated Pseudomonas aeruginosa cells in a rabbit model.
- Evaluation of corneal inflammation, ulceration, and descemetocele formation.
- Analysis of collagenase and proteoglycan-degrading enzymes in corneal tissue.
- Comparison of outcomes with and without corticosteroid treatment.
Main Results:
- Extensive polymorphonuclear leukocyte infiltration and corneal ulceration occurred within one week.
- Corticosteroid treatment significantly reduced inflammation and prevented ulceration.
- Ulcerated corneas contained collagenase and proteoglycan-degrading enzymes.
- A correlation was found between host-derived enzyme levels and corneal destruction.
Conclusions:
- Corneal destruction by Pseudomonas aeruginosa involves both bacterial proteases and host-derived enzymes.
- Host enzymes degrading collagen and proteoglycans contribute significantly to corneal pathology.
- Corticosteroids may mitigate corneal damage by modulating the host inflammatory response.