Role of fibronectin in the pathogenesis of gram-negative bacillary pneumonia.

Because the pharyngeal flora may be an important determinant of the etiology of pneumonia, the presence of gram-negative bacilli in the oropharynx might be expected to be a prelude to pneumonia due to these organisms. Colonization of the upper respiratory tract by gram-negative bacilli is correlated with adherence of gram-negative bacilli to epithelial cells. Increased adherence is associated with a loss of fibronectin from the surface of oral epithelial cells, which presumably occurs as a result of the action of secretory proteases that denude cells of fibronectin. Thus, fibronectin may be described as a modulator of the composition of the oral flora. It seems more likely that the level of protease activity or the determinants that control the level of protease activity are the true modulators of the composition of the oral flora. The delineation of these determinants should lead to a greater understanding of the pathogenesis of gram-negative bacillary pneumonia.