Abstract
Background
Early and accurate recognition of respiratory pathogens is crucial to prevent increased risk of mortality in critically ill patients. Microbial-derived volatile organic compounds (mVOCs) in exhaled breath could be used as non-invasive biomarkers of infection to support clinical diagnosis.
Methods
In this study, we investigated the diagnostic potential of
in vitro confirmed mVOCs in the exhaled breath of patients under mechanically ventilation from the BreathDx study. Samples were analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS).
Results
Pathogens from bronchoalveolar lavage (BAL) cultures were identified in 45/89 patients and
S. aureus was the most commonly identified pathogen (
n = 15). Out of 19 mVOCs detected in the
in vitro culture headspace of four common respiratory pathogens (
Staphylococcus aureus,
Pseudomonas aeruginosa,
Klebsiella pneumoniae and
Escherichia coli), 14 were found in exhaled breath samples. Higher concentrations of two mVOCs were found in the exhaled breath of patients infected with
S. aureus compared t o those without (3-methylbutanal
p < 0.01. AUROC = 0.81-0.87 and 3-methylbutanoic acid
p = 0.01. AUROC = 0.79-0.80). In addition, bacteria identified from BAL cultures which are known to metabolise tryptophan (
Escherichia coli,
Klebsiella oxytoca and
Haemophilus influenzae) were grouped and found to produce higher concentrations of indole compared to breath samples with culture-negative (
p = 0.034) and other pathogen-positive (
p = 0.049) samples.
Conclusions
This study demonstrates the capability of using mVOCs to detect the presence of specific pathogen groups with potential to support clinical diagnosis. Although not all mVOCs were found in patient samples within this sm all pilot study, further targeted and qualitative investigation is warranted using multi-centre clinical studies.
