Bacterial adherence to respiratory tract cells. Relationships between in vivo and in vitro pH and bacterial attachment

Alterations in in vitro pH have been shown to have a significant effect on the bacterial binding capacity of epithelial cells for certain organisms. We investigated the effect of in vivo pH and in vitro changes in pH on the adherence of Pseudomonas aeruginosa to buccal and tracheal cells of 19 chronic tracheostomy patients. In addition, airway pH was measured in 5 normal volunteers. Oropharyngeal and endobronchial pH were measured with a flexible electrode that could be passed through a bronchoscope under direct visualization. In vitro adherence of Pseudomonas to respiratory epithelial cells was determined at pH 6.5 and 7.2. Colonization status of the patients was determined by culture of oropharyngeal and tracheal secretions. The pH value of each site in the respiratory tract and its secretions were different in the tracheostomy patients (buccal pH 6.3; tracheal, 6.9; sputum, 7.5). No difference was noted in pH of the 2 sites in control subjects (buccal, 6.7; tracheal, 6.7). Changes in in vitro pH had a significant effect (p less than 0.004) on bacterial binding to epithelial cells from both sites. The pH had its greatest effect on tracheal cells of patients colonized with Pseudomonas. Increased in vitro binding of these organisms was noted at the more alkaline pH. The magnitude of the effect of in vitro pH alteration on bacterial binding correlated directly with the degree of binding. These results demonstrated that pH has a significant effect on in vitro Pseudomonas adherence and the effect is most marked on cells obtained from the lower respiratory tract of patients colonized with this organism.(ABSTRACT TRUNCATED AT 250 WORDS)