A multidisciplinary approach has been adopted to investigate and identify the source of malodour in washing machines and the potential for crosscontamination of laundry. Four washing machines were olfactively graded, and the number of colony-forming units (CFUs) bacteria was determined in four specific locations. Then, samples of terry-towel and fleece were washed, without the use of detergent, in the machines, and the occurrence of malodour over a 52-h period was assessed. Analysis of the scrapings from the four locations in the two malodorous machines identified a plethora of volatile organic compounds (VOCs) by either olfactory detection or mass spectral identification post-gas chromatographic separation. In addition, microbiological analysis from the swabs from the four locations within all four washing machines was carried out. Quantitative analysis of VOCs from 66 microbiological isolates from either the washing machines or fabrics was carried out. In total, 10 VOCs were identified: dimethyl disulfide, 3-methyl-1-butanol, 2,4-dithiapentane, dimethyl trisulfide, 2-tridecanone, indole, 2-phenylethanol, isovaleric acid, isobutyric acid and 1-undecene.

Aims: A novel method has been developed that allows successful differentiation between Clostridium difficile culture-positive and culturenegative stool samples based on volatile organic compound (VOC) evolution and detection by headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS). Methods and Results:The method is based on the activation of p-hydroxyphenylacetate decarboxylase produced by Cl. difficile and the detection of a specific VOC, that is 2-fluoro-4-methylphenol from an enzyme substrate. In addition, other VOCs were good indicators for Cl. difficile, that is isocaproic acid and p-cresol, although they could not be used alone for identification purposes. One hundred stool samples were tested, of which 77 were positive by culture. Detection using HS-SPME-GC-MS allowed confirmation of the presence of Cl. difficile within 18 h with a sensitivity and specificity of 83Á1 and 100%, respectively. Conclusions: It is recommended that this new approach could be used alongside conventional methods for Cl. difficile detection, including toxin detection methods, which would allow any false-negative results to be eliminated. Significance and Impact of the Study: The ability to identify Cl. difficilepositive stool samples by the analysis of VOCs could allow the development of a VOC detection device which could allow rapid diagnosis of disease and hence prompt treatment with appropriate antibiotics.

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