Augmented bacterial adherence to tracheal epithelial cells is associated with gram-negative pneumonia in an intensive care unit population

Gram-negative pneumonia is a frequent complication of intubated patients in an intensive care unit (ICU), and the adherence of the bacterial pathogen to the respiratory epithelial surface is thought to be the critical intial step in the infection process. However, the correlation between bacterial adherence to tracheal epithelial cells (TEC) and the acquisition of pneumonia and whether intubation or its duration affects bacterial adherence to TEC is unknown. To examine these factors we initially established that the normal adhesion index range for Pseudomonas aeruginosa strain 492c adherence to TEC was zero to 18.83 cfu/TEC on the basis of the adhesion indices of 12 healthy volunteers and 20 surgical patients undergoing elective bronchoscopy. Forty-two analyses of the adhesion index for P. aeruginosa binding to TEC of 24 ICU patients were performed in this study. Analysis of the data indicated that the adhesion index was not correlated with intubation or the duration of intubation. However, an elevated bacterial adhesion index was significantly (p < 0.001) correlated with pneumonitis. Pneumonitis was observed in 11 of the 12 patients who had an elevated or augmented bacterial adhesion index, whereas pneumonitis was observed in only one of 12 patients who had a normal adhesion index. The bacterial adhesion index was found to parallel the clinical situation in five patients where three patients developed high adhesion indices and acquired pneumonitis and two patients who initially had pneumonitis and elevated adhesion indices subsequently resolved their pneumonitis, and their adhesion indices fell to within the normal range.