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Structural features of tracheal tube biofilm formed during prolonged mechanical ventilation
1Department of Microbiology, National University of Singapore.
Abstract:
The dissemination of tracheal tube biofilm into the mechanically ventilated lung has been proposed as a contributory factor in the pathogenesis of ventilator-associated pneumonia. In the present study, conventional light microscopy, confocal laser scanning microscopy, and scanning electron microscopy were used to examine luminal tracheal tube biofilm in tubes from ten consecutive medical intensive care patients. Biofilms also were cultured. No tube contained a predominantly microbial aggregate. Microorganisms were either dispersed throughout the biofilm or restricted to the most superficial layer. Neutrophil polymorphonuclear cells were present in all biofilms in a pattern suggesting that a layering or stratification had taken place. The distribution of neutrophils and microorganisms was consistent with a progressive accretion of respiratory secretions, rather than formation of a predominantly microbial biofilm.
Insights
Ventilator-associated pneumonia may be linked to tracheal tube biofilm. This study found that tracheal tube contents were primarily respiratory secretions with dispersed microbes and neutrophils, not a dense microbial biofilm.
Area of Science:
- Microbiology
- Pulmonary Medicine
- Intensive Care
Background:
- Ventilator-associated pneumonia (VAP) is a serious complication in mechanically ventilated patients.
- Tracheal tube biofilm dissemination is a proposed mechanism in VAP pathogenesis.
- Understanding the composition of tracheal tube contents is crucial for VAP prevention.
Purpose of the Study:
- To investigate the structure and composition of tracheal tube biofilm.
- To determine if tracheal tube contents represent a predominantly microbial biofilm or accumulated secretions.
- To elucidate the role of microorganisms and neutrophils within the tracheal tube lumen.
Main Methods:
- Examination of tracheal tubes from 10 medical intensive care unit patients.
- Utilized conventional light microscopy, confocal laser scanning microscopy, and scanning electron microscopy.
- Cultured biofilm samples for microbial analysis.
Main Results:
- No predominantly microbial aggregate was found in any tracheal tube.
- Microorganisms were dispersed within the biofilm or confined to the superficial layer.
- All biofilms contained neutrophils, suggesting stratification and accretion of respiratory secretions rather than a microbial biofilm.
Conclusions:
- Tracheal tube contents in mechanically ventilated patients are primarily composed of respiratory secretions with dispersed microorganisms and neutrophils.
- The findings challenge the concept of a predominantly microbial biofilm as the main contributor to VAP pathogenesis via tracheal tube dissemination.
- Further research is needed to understand the precise mechanisms of VAP development in the context of tracheal tube colonization.