Role of endotracheal tube colonization in the pathogenesis of ventilator-associated pneumonias

Purpose: Ventilator-associated pneumonia (VAP) carries a high mortality rate. Colonization of the endotracheal tubes (ETT) may play a crucial role in the pathogenesis of VAP. The outer wall of the ETT is felt to be contaminated with oral flora, whereas the inner wall of the ETT may be contaminated with the suction devices. In order to improve our understanding of this phenomenum we conducted the present study. Methods: ETT removed from 19 patients were cultured following a protocol and we obtained 1)Tip inner scrapings, 2)Tip outer scrapings, 3)Tip sonication (below cuff), 4) Proximal part sonication (above the cuff). Results: 18 patients had clinico-radiological picture of pneumonia. All the ETT were heavily colonized after removal. There was no difference in the culture results between the outer or inner wall of the ETT or between above or below the cuff areas. Enterococcus (73%), Staph species (58%), and Pseudomonas sp. (32%) were the most frequent colonizers of the ETT. Only 2 of the bronchoalveolar lavage (BAL) findings coincided with the ETT cultures and 7 of the BALs were negative. Pseudomonas was isolated once in blood and ETT but not in the BAL. Conclusions: The ETT get heavy bacterial colonization as a whole: intraluminal,or extraluminal. Since many pneumonias remain undiagnosed, we hypothesize that the potential pathogen may be the one (s) colonizing the ETT. Clinical Implications: ETT cultures may be needed to ascertain diagnosis of VAP.