Open Access Highly Accessed Research article

Molecular analysis of volatile metabolites released specifically by staphylococcus aureus and pseudomonas aeruginosa

Wojciech Filipiak12, Andreas Sponring12, Maria Magdalena Baur12, Anna Filipiak12, Clemens Ager12, Helmut Wiesenhofer12, Markus Nagl3, Jakob Troppmair4* and Anton Amann12*

Author Affiliations

1 Breath Research Institute of the Austrian Academy of Sciences, Rathausplatz 4, A-6850, Dornbirn, Austria

2 Univ. Clinic for Anesthesia, Innsbruck Medical University, Anichstr. 35, Innsbruck, A-6020, Austria

3 Department of Hygiene, Microbiology and Social Medicine, Division of Hygiene and Medical Microbiology, Innsbruck Medical University, Fritz-Preglstra├če 3, Innsbruck, A-6020, Austria

4 Daniel-Swarovski Research Laboratory, Department of Visceral-, Transplant- and Thoracic Surgery, Innsbruck Medical University, Innrain 66, A-6020, Innsbruck, Austria

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BMC Microbiology 2012, 12:113  doi:10.1186/1471-2180-12-113

Published: 20 June 2012

Abstract

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.

Keywords:
Volatile organic compounds (VOCs); Gas chromatography mass spectrometry (GCMS); Breath analysis; In vitro headspace sampling; Adsorptive enrichment; Multibed sorption tubes; Volatile metabolites; Staphylococcus aureus; Pseudomonas aeruginosa