Abstract
Pseudomonas aeruginosa is a leading cause of human morbidity and mortality that often targets epithelial surfaces. Host immunocompromise, or the presence of indwelling medical devices, including contact lenses, can predispose to infection. While medical devices are known to accumulate bacterial biofilms, it is not well understood why resistant epithelial surfaces become susceptible to P. aeruginosa. Many bacteria, including P. aeruginosa, release outer membrane vesicles (OMVs) in response to stress that can fuse with host cells to alter their function. Here, we tested the hypothesis that mucosal fluid can trigger OMV release to compromise an epithelial barrier. This was tested using tear fluid and corneal epithelial cells in vitro and in vivo. After 1 h both human tear fluid, and the tear component lysozyme, greatly enhanced OMV release from P. aeruginosa strain PAO1 compared to phosphate buffered saline (PBS) controls (∼100-fold). Transmission electron microscopy (TEM) and SDS-PAGE showed tear fluid and lysozyme-induced OMVs were similar in size and protein composition, but differed from biofilm-harvested OMVs, the latter smaller with fewer proteins. Lysozyme-induced OMVs were cytotoxic to human corneal epithelial cells in vitro and murine corneal epithelium in vivo. OMV exposure in vivo enhanced Ly6G/C expression at the corneal surface, suggesting myeloid cell recruitment, and primed the cornea for bacterial adhesion (∼4-fold, P < 0.01). Sonication disrupted OMVs retained cytotoxic activity, but did not promote adhesion, suggesting the latter required OMV-mediated events beyond cell killing. These data suggest that mucosal fluid induced P. aeruginosa OMVs could contribute to loss of epithelial barrier function during medical device-related infections.
Highlights
Contact lenses are among the indwelling medical devices that can promote bacterial-induced pathology
We explored if P. aeruginosa-derived outer membrane vesicles (OMVs) could compromise corneal epithelial barrier function
The results revealed no significant difference in the number of bacteria that traverse the cells after the 1 h pretreatment with OMVs (Figure 5B, gray bars)
Summary
Contact lenses are among the indwelling medical devices that can promote bacterial-induced pathology. In addition to sight-threatening corneal infection, microbial contamination of lenses and lens cases can cause various potentially serious and/or painful inflammatory events including contact lens-related acute red eye (CLARE), contact lens-induced peripheral. Pseudomonas aeruginosa has been the most common cause of contact lens-related corneal infection since soft contact lenses were introduced in the early 1970’s (Stapleton and Carnt, 2012). We have shown that the same bacteria can reliably infect the cornea in a (rat) lens-wearing model if given sufficient time, even if very small inocula are used (Tam et al, 2010). Since lenses removed from infected eyes caused disease faster than lenses inoculated in vitro, the data suggested that bacteria launched additional virulence factors when adapted to the eye-lens environment
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