Environmental factors influence P-aeruginosa binding to the wounded mouse cornea

Purpose. To determine whether environmental factors or bacterial viability affect the binding of two strains of P. aeruginosa to mouse cornea. Methods. Scarified corneas were placed in organ culture and inoculated with P. aeruginosa cell suspensions containing either ATCC 19660 or PAO1 bacterial strains classed as cytotoxic or invasive, respectively. Eyes were incubated in vitro for 1 h after bacterial application at different pH or temperature conditions or in PBS containing various divalent cations. The adhesion of heat-killed or formalin-fixed bacteria was tested similarly. Scanning electron microscopy (scanning EM) was used to quantitate adherent bacteria. Results. P. aeruginosa ATCC 19660 showed an increase in binding at pH 8.0, favored higher temperatures and required both calcium and magnesium for optimum binding. Adherence of PAO 1 was enhanced at pH 6.5 and decreased at pH 8.0. This strain favored binding at lower temperatures and did not require either divalent cation for optimum binding. In addition, the presence of magnesium ions resulted in reduced binding for this strain. Both strains exhibited less binding ability after formalin fixation or heat killing. Conclusion. Environmental factors and bacterial viability are important factors which influence the ability of both cytotoxic and invasive strains of P. aeruginosa to bind to the scarified cornea.