Description and microbiology of endotracheal tube biofilm in mechanically ventilated subjects.

Background: A biofilm is found on the inner side of endotracheal tubes (ETT) in mechanically ventilated patients, but its features and role in pneumonia remain unclear.

Methods: This prospective, observational, monocentric study included critically ill ventilated subjects. Measurement of the ETT inner volume was first performed before extubation using the acoustic reflection method. After extubation, the biofilm was studied by means of optical and atomic force microscopy. Bacteriological analysis was then performed and compared with clinical documentation.

Results: Twenty-four subjects were included. Duration of intubation lasted from 2 to 79 d (mean ± SD: 11 ± 15 d). The mean percentage of ETT volume loss evaluated in situ (n = 21) was 7.1% and was not linked with the duration of intubation. Analyses with atomic force microscopy (n = 6) showed a full coverage of the inner part of the tube with biofilm, even after saline rinse. Its thickness ranged from 0.8 to 5 μm. Bacteriological cultures of the biofilm (n = 22) often showed the same bacteria as in tracheal secretions, especially for pathogenic organisms. Pseudomonas aeruginosa and Candida albicans were among the most frequent microorganisms. In subjects who had experienced a successfully treated episode of ventilator-associated pneumonia (n = 5), the responsible bacteria were still present in the biofilm.

Conclusions: ETT biofilm is always present in intubated patients whatever the duration of intubation and appears quickly after intubation. Even after soft rinse, a small but measurable part of biofilm remains always present, and seems strongly adherent to the ETT lumen. It contains potentially pathogenic bacteria for the lung.