School of Optometry and Vision Science, The University of New South Wales, UNSW, Sydney, NSW, 2052, Australia.
Minomic International Ltd, Macquarie Park, NSW, 2113, Australia.
Exp Eye Res. 2020 Apr;193:107994. doi: 10.1016/j.exer.2020.107994. Epub 2020 Mar 5.
Staphylococcus aureus is a common bacterial isolate from cases of microbial keratitis. The virulence factors that contribute to its pathogenicity during this disease have not been fully resolved. The aim of the current study was to examine the effects of the extracellular protease Staphopain A on corneal virulence. Two strains were used, one Staph 38 that gives a high pathology score during keratitis and a less virulent strain ATCC 8325-4. The effect of inhibition of Staphopain by general or specific protease inhibitors on adhesion of strains to fibronectin-coated glass or PMMA was determined. This was followed by an analysis of the effect of Staphopain A on the ability of the bacteria to adhere to and invade corneal epithelial cells. Finally, the effect of inhibiting Staphopain A on pathogenesis in a mouse model of keratitis was studied. Staphopain A increased the adhesion of strains to fibronectin-coated substrata and inhibition of Staphopain A reduced adhesion. The inhibition of Staphopain A by staphostatin A significantly decreased both association with and invasion into human corneal epithelial cells by 15-fold for strain Saur38. Inhibition of Staphopain A significantly reduced the pathology associated with S. aureus keratitis, reducing the infecting numbers of bacteria from 1.8x10 to <1x10 cells/cornea (p ≤ 0.001), significantly reducing the corneal pathology score (p ≤ 0.038) and reducing the numbers of infiltrating PMNs. This study shows that Staphopain increases adhesion and invasion of corneal cells due to increasing fibronectin binding and its inhibition has a significant impact on pathogenicity of S. aureus during keratitis.
金黄色葡萄球菌是微生物角膜炎病例中常见的细菌分离株。导致其在该疾病中致病性的毒力因子尚未完全确定。本研究旨在研究细胞外蛋白酶 Staphopain A 对角膜毒力的影响。使用了两种菌株，一种是在角膜炎中产生高病理评分的 Staph 38 菌株，另一种是毒力较低的 ATCC 8325-4 菌株。通过使用一般或特异性蛋白酶抑制剂抑制 Staphopain 对菌株在纤维连接蛋白包被玻璃或 PMMA 上的粘附的影响进行了测定。随后分析了 Staphopain A 对细菌粘附和侵袭角膜上皮细胞能力的影响。最后，研究了抑制 Staphopain A 对金黄色葡萄球菌角膜炎小鼠模型发病机制的影响。Staphopain A 增加了菌株对纤维连接蛋白包被基底的粘附，而 Staphopain A 的抑制减少了粘附。Staphostatin A 对 Staphopain A 的抑制显著降低了 Saur38 菌株与和侵袭人角膜上皮细胞的关联，降低了 15 倍。抑制 Staphopain A 显著降低了与金黄色葡萄球菌角膜炎相关的病理学，将感染的细菌数量从 1.8x10 减少到 <1x10 个/角膜（p≤0.001），显著降低了角膜病理评分（p≤0.038）并减少了浸润的 PMN 数量。本研究表明，Staphopain 通过增加纤维连接蛋白结合来增加角膜细胞的粘附和侵袭，其抑制对金黄色葡萄球菌角膜炎的致病性有显著影响。
