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Pseudomonas aeruginosa Keratitis: Protease IV and PASP as Corneal Virulence Mediators

Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS 39216, USA
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Microorganisms 2019, 7(9), 281; https://doi.org/10.3390/microorganisms7090281
Received: 29 July 2019 / Revised: 12 August 2019 / Accepted: 15 August 2019 / Published: 22 August 2019
(This article belongs to the Special Issue Insights Into The Molecular Pathogenesis of Ocular Infections)
Pseudomonas aeruginosa is a leading cause of bacterial keratitis, especially in users of contact lenses. These infections are characterized by extensive degradation of the corneal tissue mediated by Pseudomonas protease activities, including both Pseudomonas protease IV (PIV) and the P. aeruginosa small protease (PASP). The virulence role of PIV was determined by the reduced virulence of a PIV-deficient mutant relative to its parent strain and the mutant after genetic complementation (rescue). Additionally, the non-ocular pathogen Pseudomonas putida acquired corneal virulence when it produced active PIV from a plasmid-borne piv gene. The virulence of PIV is not limited to the mammalian cornea, as evidenced by its destruction of respiratory surfactant proteins and the cytokine interleukin-22 (IL-22), the key inducer of anti-bacterial peptides. Furthermore, PIV contributes to the P. aeruginosa infection of both insects and plants. A possible limitation of PIV is its inefficient digestion of collagens; however, PASP, in addition to cleaving multiple soluble proteins, is able to efficiently cleave collagens. A PASP-deficient mutant lacks the corneal virulence of its parent or rescue strain evidencing its contribution to corneal damage, especially epithelial erosion. Pseudomonas-secreted proteases contribute importantly to infections of the cornea, mammalian lung, insects, and plants. View Full-Text
Keywords: Pseudomonas aeruginosa; bacterial keratitis; corneal virulence; protease IV (PIV); P. aeruginosa small protease (PASP); catalytic triad; corneal ulcer; respiratory infection; insect infection; plant infection Pseudomonas aeruginosa; bacterial keratitis; corneal virulence; protease IV (PIV); P. aeruginosa small protease (PASP); catalytic triad; corneal ulcer; respiratory infection; insect infection; plant infection
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O’Callaghan, R.; Caballero, A.; Tang, A.; Bierdeman, M. Pseudomonas aeruginosa Keratitis: Protease IV and PASP as Corneal Virulence Mediators. Microorganisms 2019, 7, 281.

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