Association of Respiratory Tract Colonization with Adherence of Gram-Negative Bacilli to Epithelial Cells

Abstract

Factors that promote oropharyngeal colonization of seriously ill patients with gram-negative bacilli are poorly understood. Of 34 subjects who required intensive care, 18 (53%) were colonized with gram-negative bacilli. Oropharyngeal epithelial cells of all colonized patients contained adherent bacilli. Fewer .alpha.-hemolytic streptococci but greater numbers of Pseudomonas aeruginosa and Klebsiella pneumoniae (P = 0.01) adhered in vitro to buccal epithelial cells from colonized patients than to cells from non-colonized patients. Adherence of bacilli to buccal cells was inhibited in vitro by concanavalin A but not by bovine serum albumin or phytohemagglutinin. Brief exposure of buccal cells to trypsin increased adherence of bacilli. Prior adherence of 1 spp. of bacilli inhibited subsequent adherence of a 2nd spp. Epithelial cells of the upper respiratory tract may contain binding sites for gram-negative bacilli. Factors associated with serious illness appear to increase the availability of these binding sites, thus facilitating colonization of the upper respiratory tract with gram-negative bacilli.