Molecular analysis of volatile metabolites released specifically by Staphylococcus aureus and Pseudomonas aeruginosa.
BACKGROUND
The routinely used microbiological diagnosis of ventilator associated pneumonia (VAP) is time consuming and often requires invasive methods for collection of human specimens (e.g. bronchoscopy). Therefore, it is of utmost interest to develop a non-invasive method for the early detection of bacterial infection in ventilated patients, preferably allowing the identification of the specific pathogens. The present work is an attempt to identify pathogen-derived volatile biomarkers in breath that can be used for early and non- invasive diagnosis of ventilator associated pneumonia (VAP). For this purpose, in vitro experiments with bacteria most frequently found in VAP patients, i.e. Staphylococcus aureus and Pseudomonas aeruginosa, were performed to investigate the release or consumption of volatile organic compounds (VOCs).


RESULTS
Headspace samples were collected and preconcentrated on multibed sorption tubes at different time points and subsequently analyzed with gas chromatography mass spectrometry (GC-MS). As many as 32 and 37 volatile metabolites were released by S. aureus and P. aeruginosa, respectively. Distinct differences in the bacteria-specific VOC profiles were found, especially with regard to aldehydes (e.g. acetaldehyde, 3-methylbutanal), which were taken up only by P. aeruginosa but released by S. aureus. Differences in concentration profiles were also found for acids (e.g. isovaleric acid), ketones (e.g. acetoin, 2-nonanone), hydrocarbons (e.g. 2-butene, 1,10-undecadiene), alcohols (e.g. 2-methyl-1-propanol, 2-butanol), esters (e.g. ethyl formate, methyl 2-methylbutyrate), volatile sulfur compounds (VSCs, e.g. dimethylsulfide) and volatile nitrogen compounds (VNCs, e.g. 3-methylpyrrole).Importantly, a significant VOC release was found already 1.5 hours after culture start, corresponding to cell numbers of ~8*106 [CFUs/ml].


CONCLUSIONS
The results obtained provide strong evidence that the detection and perhaps even identification of bacteria could be achieved by determination of characteristic volatile metabolites, supporting the clinical use of breath-gas analysis as non-invasive method for early detection of bacterial lung infections.
Breath Research Institute of the Austrian Academy of Sciences, Rathausplatz 4, A-6850, Dornbirn, Austria.
Wojciech
W
Filipiak
Andreas
A
Sponring
Maria Magdalena
MM
Baur
Anna
A
Filipiak
Clemens
C
Ager
Helmut
H
Wiesenhofer
Markus
M
Nagl
Jakob
J
Troppmair
Anton
A
Amann
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001424:Bacterial Infections / Q000175:diagnosis / Q000382:microbiology; D001944:Breath Tests; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008171:Lung Diseases / Q000175:diagnosis / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000145:classification / Q000378:metabolism*; D055549:Volatile Organic Compounds / Q000032:analysis*; D055815:Young Adult
D055549:Volatile Organic Compounds