Dartnell, LR; Roberts, TA; Moore, G; Ward, JM; Muller, JP; (2013) Fluorescence characterization of clinically-important bacteria. PLoS One , 8 (9) , Article e75270. 10.1371/journal.pone.0075270.

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Preview	Other (TIFF Figure 1. Photographs of solid surfaces typical of a hospital ward analysed for background fluorescence.) journal.pone.0075270.g001.tif Download (2MB)
Preview	Other (TIFF Figure 2. Excitation-emission matrices (EEMs) of the complete fluorescence response exhibited by clinically relevant Gram positive bacteria.) journal.pone.0075270.g002.tif Download (1MB)
Preview	Other (TIFF Figure 3. EEMs of the complete fluorescence response exhibited by clinically-important Gram negative bacteria) journal.pone.0075270.g003.tif Download (1MB)
Preview	Other (TIFF Figure 4. EEMs of two hospital cleaning fluids, Actichlor (left) and Tristel Fuse (right).) journal.pone.0075270.g004.tif Download (398kB)
Preview	Other (TIFF Figure 5. EEMs of the fluorescence response of equipment commonly found in a clinical setting) journal.pone.0075270.g005.tif Download (990kB)
Preview	Other (TIFF Figure 6. EEMs of the fluorescence response of different components of the patient nurse call button) journal.pone.0075270.g006.tif Download (972kB)
Preview	Other (TIFF Figure 7. EEMs of different bed rail materials found on wards) journal.pone.0075270.g007.tif Download (1MB)
Preview	Other (TIFF Figure 8. EEMs (arbitrary intensity units) produced by microfiber cleaning cloth (greyscale) and S. aureus (colour).) journal.pone.0075270.g008.tif Download (282kB)

Abstract

Healthcare-associated infections (HCAI/HAI) represent a substantial threat to patient health during hospitalization and incur billions of dollars additional cost for subsequent treatment. One promising method for the detection of bacterial contamination in a clinical setting before an HAI outbreak occurs is to exploit native fluorescence of cellular molecules for a hand-held, rapid-sweep surveillance instrument. Previous studies have shown fluorescence-based detection to be sensitive and effective for food-borne and environmental microorganisms, and even to be able to distinguish between cell types, but this powerful technique has not yet been deployed on the macroscale for the primary surveillance of contamination in healthcare facilities to prevent HAI. Here we report experimental data for the specification and design of such a fluorescence-based detection instrument. We have characterized the complete fluorescence response of eleven clinically-relevant bacteria by generating excitation-emission matrices (EEMs) over broad wavelength ranges. Furthermore, a number of surfaces and items of equipment commonly present on a ward, and potentially responsible for pathogen transfer, have been analyzed for potential issues of background fluorescence masking the signal from contaminant bacteria. These include bedside handrails, nurse call button, blood pressure cuff and ward computer keyboard, as well as disinfectant cleaning products and microfiber cloth. All examined bacterial strains exhibited a distinctive double-peak fluorescence feature associated with tryptophan with no other cellular fluorophore detected. Thus, this fluorescence survey found that an emission peak of 340nm, from an excitation source at 280nm, was the cellular fluorescence signal to target for detection of bacterial contamination. The majority of materials analysed offer a spectral window through which bacterial contamination could indeed be detected. A few instances were found of potential problems of background fluorescence masking that of bacteria, but in the case of the microfiber cleaning cloth, imaging techniques could morphologically distinguish between stray strands and bacterial contamination.

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