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Key role of fibronectin for Staphylococcus aureus adherence to ex vivo corneal epithelium
Author(s) -
Maurin Corantin,
Courrier Emilie,
He Zhiguo,
Josselin Rigaill,
Frédéric Laurent,
Thuret Gilles,
Gain Philippe,
Verhoeven Paul
Publication year - 2021
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2020.0109
Subject(s) - bacterial adhesin , keratitis , corneal epithelium , staphylococcus aureus , microbiology and biotechnology , epithelium , cornea , ex vivo , panton–valentine leukocidin , fibronectin , keratoconus , immunostaining , biology , medicine , immunology , in vivo , pathology , methicillin resistant staphylococcus aureus , virulence , cell , bacteria , ophthalmology , immunohistochemistry , biochemistry , gene , genetics
Purpose Staphylococcus aureus (SA) is the second most frequent pathogen of bacterial keratitis. Fibronectin‐binding proteins (FnBPs) which are staphylococcal adhesins are found in 95% of clinical isolates and are shown to be important adhesins or invasion factors in ulcerative keratitis. Aim: to study the role of the fibronectin (Fn) in SA adherence on corneal epithelium and its role in the initiation of the keratitis. Methods We used 4 strains of SA: 8325‐4 and DU5883 (8325‐4 isogenic strain lacking in fnbA/B), and SA113 and SA113 srtA‐ (Isogenic strain lacking in Sortase A). Levels of internalisation were measured by lysostaphin protection assay on human corneal epithelial HCE‐2 cells. SA adherence level was calculated by determining the ratio between the SA area and area of corneal epithelial ulceration blocked by Fn antibodies or not. The surface of epithelial ulceration was defined with Fn immunostaining. Results On cells, intracellular loads of 8325‐4 and DU5883 strains were, respectively, 4.2 and 2.6 log CFU/106 cells (p < 0.0001) and intracellular loads of SA113 and SA113 srtA‐ strains were, respectively, 4.3 and 3.9 log CFU/106 cells (p < 0.0001). Onto intact and injured corneal epithelium, SA (8325‐4) adherence level was, respectively, 0.04 and 4.36 MFI (Mean Fluorescence Intensity) (p = 0.0003). On injured corneal epithelium, adherence level of 8325‐4 and DU5883 was significantly reduced from 3.7% to 0.5%, respectively (p < 0.001), whereas adherence level of SA113 Wt and srtA‐ was not significantly reduced from 1.5% to 0.7%, respectively (p = 0.1873). Blockage of Fn showed a significant decrease of 87%, 85% and 86% of the 8325‐4, SA13 WT and SA113 SrtA‐ adhesion level, respectively, but a not significant decrease for DU5883 (43%). Conclusions Capacity of SA to bind the epithelium of intact cornea was weak, whereas corneal epithelium ulceration significantly increased its adherence. Adherence is mediated by the presence of Fn inside the epithelium, FnBPs and adhesine proteins in SA.