Implications of endotracheal tube biofilm in ventilator-associated pneumonia response: a state of concept

Abstract

Introduction: Biofilm in endotracheal tubes (ETT) of ventilated patients has been suggested to play a role in the development of ventilator-associated pneumonia (VAP). Our purpose was to analyze the formation of ETT biofilm and its implication in the response and relapse of VAP.

Methods: We performed a prospective, observational study in a medical intensive care unit. Patients mechanically ventilated for more than 24 hours were consecutively included. We obtained surveillance endotracheal aspirates (ETA) twice weekly and, at extubation, ETTs were processed for microbiological assessment and scanning electron microscopy.

Results: Eighty-seven percent of the patients were colonized based on ETA cultures. Biofilm was found in 95% of the ETTs. In 56% of the cases, the same microorganism grew in ETA and biofilm. In both samples the most frequent bacteria isolated were Acinetobacter baumannii and Pseudomonas aeruginosa. Nineteen percent of the patients developed VAP (N = 14), and etiology was predicted by ETA in 100% of the cases. Despite appropriate antibiotic treatment, bacteria involved in VAP were found in biofilm (50%). In this situation, microbial persistence and impaired response to treatment (treatment failure and relapse) were more frequent (100% vs 29%, P = 0.021; 57% vs 14%, P = 0.133).

Conclusions: Airway bacterial colonization and biofilm formation on ETTs are early and frequent events in ventilated patients. There is microbiological continuity between airway colonization, biofilm formation and VAP development. Biofilm stands as a pathogenic mechanism for microbial persistence, and impaired response to treatment in VAP.

Figure 1

Scanning electron microscopy micrographs of biofilm in the endotracheal tubes. Biofilm at low magnification is composed of a matrix that attaches on the surface of the ETT. Scale bar: 2 μm.

Figure 2

Identification of microorganisms on the surface of biofilm. In certain cases we could identify microorganisms immersed in the biofilm matrix. A) Cocci, scale bar: 2 μm, B-D) Bacilli, scale bar: 4 μm, 2 μm and 5 μm, respectively, and E) yeast. Scale bar: 10 μm.

Figure 3

Relationship between biofilm, microbial persistence and treatment failure. Bar graph representative of the percentage of cases in which there was (gray) or not (black) bacterial survival on ETT biofilm despite appropriate treatment. Microbial persistence in respiratory samples and treatment failure were more frequent when bacterial growth was documented in ETT.