Bacterial adherence to epithelial cells in bacillary colonization of the respiratory tract

Bacterial colonization of mucosal surfaces may be mediated by bacterial adherence to epithelial cells. To study the role of adherence in gram-negative bacillary colonization of the upper respiratory tract, we studied 32 noncolonized patients undergoing elective surgery. Adherence of Pseudomonas aeruginosa and 3 other bacilli to patients' buccal cells in vitro was studied pre- and postoperatively; results were correlated with occurrence of bacillary colonization of the oropharynx in vivo. Adherence of all species was similar. Preoperatively, mean +/- SD adherence was 4.3 +/- 2.0 Pseudomonas aeruginosa/cell. Postoperatively, adherence of Pseudomonas aeruginosa exceeded 8.3 (preoperative mean + 2 SD) bacilli/cell in 16 patients, 11 (69%) of whom became colonized. None of 16 patients whose cells adhered fewer than 8.3 bacilli/cell postoperatively became colonized. Buccal cell binding of 3H-concanavalin A was increased both pre- and postoperatively among patients who became colonized. Gram-negative bacillary colonization of the upper respiratory tract is associated with increased adherence of bacilli to buccal cells. Epithelial cell binding may provide the mechanism whereby ill patients are rendered susceptible to colonization.