[Observation of biofilms inside tracheal tubes by electron microscopy and the relationship between biofilms and VAP]

To observe the formation of biofilms inside tracheal tubes and to evaluate the effect of biofilm on the development of ventilator associated pneumonia (VAP).

Biofilms inside tracheal tubes from intubated patients were observed by scanning electron microscopy and transmission electron microscopy, meanwhile bacteria were detected in the specimens from the lower respiratory tract and the inside of tracheal tubes.

76% (19/25) of inner surface of tracheal tubes was coated with a confluent amorphous matrix by scanning electron microscopy. The average duration of trach-intubation in this group [(10.7 +/- 7.9) days] was longer than that in the other group [(2.1 +/- 0.8) days] in which tracheal tubes were not coated with the confluent amorphous matrix (P < 0.05). The presence of many bacteria(14/18) within these amorphous matrix was confirmed by transmission electron microscopy. Of the sixteen tracheal tubes, eleven tubes grew the same organisms that had been isolated from the secretions of the lower respiratory tract before extubation. In some VAP patients (7/8), organisms isolated from tracheal tubes were the same organisms which were pathogenic organisms of VAP.

There was a close connection between the formation of bacterial BF and the long-term indwelling tracheal tubes. The presence of bacterial BF in the inner of tracheal tubes might be associated with the pathogenic organisms of VAP.