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Cystic fibrosis: bench to bedside
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S81 DEVELOPING A NON-INVASIVE TEST FOR PSEUDOMONAS DETECTION: TOWARDS AN ELECTRONIC NOSE

1S Savelev, 1A De Soyza, 2A Nicholson, 2J Perry, 1M Petrie, 1R Taylor, 3SJ Bourke, 1AJ Fisher, 1PA Corris. 1Institute for Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK, 2Dept Medical Microbiology, Freeman Hospital, Newcastle University, Newcastle upon Tyne, UK, 3Cystic Fibrosis Unit, Royal Victoria Infirmary, Newcastle upon Tyne, UK

Background: Pseudomonas aeruginosa (PA) is a key respiratory pathogen with a distinctive odour in culture. Volatile organic compounds (VOC) are a likely cause of this odour and have previously been detected in the headspace gases of bacterial cultures. Diagnostic improvements are required for the early detection of Pseudomonas infection in at-risk groups such as cystic fibrosis. Limitations in sputum collection (eg, children unable to expectorate) and culture (overgrowth by other bacteria) mean prompt PA eradication therapy may be denied to patients.

Hypothesis: Determining VOC in headspace gases, sputum and exhaled breath may offer benefits in addition to standard culture.

Methods: Solid phase micro-extraction gas chromatography mass spectrometry (SPME–GCMS) using fibres was used to collect headspace gas volatiles initially from overnight bacterial cultures of known cystic fibrosis pathogens or PA. 40 sputum samples were collected from cystic fibrosis and non-cystic fibrosis bronchiectasis clinics and headspace gas analysis after 15 minutes at 37° was compared with 24–48-h standard microbiology culture results. Once potential markers were identified, 10 patients underwent exhaled breath testing using a modified spacer device containing a SPME fibre.

Results: In vitro cultures; azridine was noted in 5/6 PA strains but none of the other bacteria tested (n  =  6 including Staphylococcus aureus, Pseudomonas putida and Escherichia coli). In 40 sputum specimens culture revealed PA in 28 and the absence of PA in 12. The headspace gases analysis of the corresponding sputum (in vivo) revealed that azridine …

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