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Ilham Putra, Khandaker Nasim Anwar, Xiang Shen, Behnam Rabiee, Dominique Missiakas, Medi Eslani, Ali R Djalilian; The role of Staphylococcus aureus alpha-toxin on corneal epithelial wound healing. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4360.
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© ARVO (1962-2015); The Authors (2016-present)
Staphylococcus aureus (S aureus) is a common cause of bacterial infections in the cornea. It has also been shown colonization by S aureus leads to delayed and abnormal corneal wound healing. We evaluated the effects of S aureus alpha-toxin (wild type) on corneal epithelial wound healing.
The effect of live wild type and wild type conditioned media (CM) on corneal epithelial wound healing was tested using the scratch assay on telomerase-immortalized human corneal epithelial cells (HCEC) in vitro and central 2-mm corneal epithelial debridement model in C57bl/6J mice. The invasiveness of the wild type and isogenic hla mutant strains of S. aureus was evaluated in human corneal epithelial cells in vitro and also in a murine keratitis model in vivo study.
Both wild type and wild type CM significantly delayed corneal epithelial wound healing in vitro and in vivo. After 6 hours, wound closure ratio (WCR) was 9 ± 6 percent after incubation with wild type CM compared to 48 ± 9 percent with unconditioned media in vitro (P<0.001). In vivo, WCR after 24 hours was 23 ± 16 percent compared to 80 ± 5 percent, respectively (P<0.001). Heating the CM abrogated its inhibitory effect and increased WCR to 54 ± 5 percent in vitro and 48 ± 8 percent in vivo (P<0.001 compared to wild type CM). Similarly, isogenic hla mutant strains S aureus had significantly less inhibitory effect on wound healing with WCR of 43 ± 10 percent in vitro and 72 ± 8 percent in vivo compared to the wild type (P<0.05). Hla mutant strains S aureus was less able to invade human corneal epithelial cells in vitro with 34250 ± 5737 mean bacterial count inside the cells (BC) compared to 6032 ± 7506 BC with wild type and in vivo, with 84750 ± 16660 BC and 34805 ± 46611 BC, respectively (P<0.001 for all comparisons).
Alpha-toxin plays a major pathogenic role both in the invasiveness of S aureus and its pathologic modulation of corneal epithelial wound healing. Targeting alpha toxin may provide a new therapy to modulate S aureus pathogenesis on the cornea.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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