Factors Influencing the Adherence of Pseudomonas aeruginosa to Mammalian Buccal Epithelial Cells

Abstract

A correlation has previously been demonstrated between the in vitro adherence of Pseudomonas aeruginosa to upper respiratory tract epithelium of seriously ill patients and subsequent colonization of the respiratory tract by this opportunistic pathogen. Although the specific in vivo alterations in the cell surface that permit the adherence of P. aeruginosa have not been defined, we have demonstrated that P. aeruginosa adherence in vitro can be correlated with the loss of a protease-sensitive glycoprotein, fibronectin, from the cell surface. The object of these studies was to correlate in vitro adherence of P. aeruginosa to buccal epithelial cells from patients with the levels of cell-surface fibronectin and of salivary proteases from the same patients, as well as to define the structure(s) on the bacterial surface important in the adherence process. A direct radioimmuno-binding assay was developed to measure cell-surface fibronectin, while protease activity in secretions was measured by ¹²⁵I release from ¹²⁵I-labelled insoluble fibrin matrices. Adherence of radiolabeled P. aeruginosa was directly related to decreased amounts of cell-surface fibronectin (P < .001) and increased levels of salivary protease (P < .001). Additionally, we demonstrated that pili may mediate the adherence of P. aeruginosa to buccal cells. This was shown by the ability of purified pili, when preincubated with buccal cells, to decrease the adherence of intact organisms from a mean of 30.6 organisms/cell to 5.7 organisms/cell (P < .01).