Pseudomonas aeruginosa small protease (PASP), a keratitis virulence factor

Area of Science:

• Ophthalmology
• Microbiology
• Protease Function

Background:

• Pseudomonas aeruginosa is a major cause of bacterial keratitis.
• Secreted proteases play a role in bacterial pathogenesis.
• The specific contribution of P. aeruginosa small protease (PASP) to keratitis is not well understood.

Purpose of the Study:

• To investigate the role of PASP in the pathogenesis of experimental keratitis.
• To compare the virulence of a PASP-deficient mutant with its parent and rescue strains in vivo.

Main Methods:

• Construction of a PASP-deficient P. aeruginosa mutant using allelic exchange.
• Generation of a PASP rescue strain.
• Evaluation of corneal virulence in rabbit and mouse keratitis models using clinical scoring, bacterial counts, and histopathology.
• Assessment of PASP's degradation activity on host proteins and tear film components.

Main Results:

• PASP-deficient mutant exhibited significantly lower clinical scores and reduced corneal pathology in both rabbit and mouse models compared to parent and rescue strains.
• Bacterial growth was comparable across all strains in the rabbit cornea.
• PASP demonstrated degradation of complement C3, fibrinogen, LL-37, and tear film constituents.

Conclusions:

• PASP is a significant virulence factor for P. aeruginosa in experimental keratitis.
• PASP contributes to keratitis pathogenesis by degrading key host defense proteins and tear film components.