Identification of Potential Urinary Metabolite Biomarkers of Ventilator-Associated Pneumonia.

Introduction: Ventilator-associated pneumonia (VAP) caused by is a major cause of morbidity and mortality in hospital intensive care units (ICU). Rapid identification of -derived markers in easily accessible patients' samples can enable an early detection of VAP (VAP-PA), thereby stewarding antibiotic use and improving clinical outcomes.

Methods: Metabolites were analysed using liquid chromatography-mass spectrometry (LC-MS) in prospectively collected urine samples from mechanically ventilated patients admitted to the Antwerp University Hospital ICU. Patients were followed from the start of mechanical ventilation (n = 100 patients) till the time of clinical diagnosis of VAP (n = 13). Patients (n = 8) in whom diagnosis of VAP was further confirmed by culturing respiratory samples and urine samples were studied for semi-quantitative metabolomics.

Results: We first show that multivariate analyses highly discriminated VAP-PA from VAP-non-PA as well as from the pre-infection groups (  = .97 and .98, respectively). A further univariate analysis identified 58 metabolites that were significantly elevated or uniquely present in VAP-PA compared to the VAP-non-PA and pre-infection groups ( < .05). These comprised both a known metabolite of histidine as well as a novel nicotine metabolite. Most interestingly, we identified 3 metabolites that were not only highly upregulated for, but were also highly specific to, VAP-PA, as these metabolites were completely absent in all pre-infection timepoints and in VAP-non-PA group.

Conclusions: Considerable differences exist between urine metabolites in VAP-PA compared to VAP due to other bacterial aetiologies as well to non-VAP (pre-infection) timepoints. The unique urinary metabolic biomarkers we describe here, if further validated, could serve as highly specific diagnostic biomarkers of VAP-PA.