Physicochemical Characterization of Gallstone Surfaces to Predict Their Interaction with Salmonella Typhi.

Salmonella Typhi can adhere to and build biofilms on the surface of gallstones causing abnormal gallbladder mucosa, which could lead to carcinogenesis. The surface physicochemical properties of microbial cells and materials have been shown to play a crucial role in adhesion. Therefore, the purpose of this study was to investigate, for the first time, the surface properties of nine gallstones and to evaluate the influence of these parameters on the theoretical adhesion of S. Typhi to gallstone surfaces. The physicochemical properties were determined by SEM-EDX and contact angle measurements (CAM) while the predictive adhesion of S. Typhi on gallstones was estimated using the XDLVO approach. SEM-EDX analysis revealed that cholesterol is the principal component on the surface of all gallstones, with carbon and oxygen as the main elements. Aluminum was detected as a trace element in only three gallstones: GS2, GS4, and GS5. S. Typhi CIP5535 has a hydrophilic character (ΔG_iwi = 33.54 mJ m^-2), as well as strong electron donor (γ^- = 55,80 mJ m^-2) and weak electron acceptor properties (γ⁺  = 1,95 mJ m^-2). Regarding gallstones, it was found that they have a hydrophobic character (ΔG_iwi between -29,9 mJ m^-2 and -75,2 mJ m^-2), while their electron donor/acceptor characters change according to each gallstone. Predictive adhesion showed that all gallstones could be colonized by S. Typhi $\left(\Delta G_{\text{XDLVO}}^{\text{Total}}<0\right)$ except GS1, GS5, and GS6 $\left(\Delta G_{\text{XDLVO}}^{\text{Total}}>0\right)$ . Understanding the interfacial phenomena implicated in the process of bacterial adhesion makes it possible to limit or even inhibit the adhesion of S. Typhi on gallstone surfaces.