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UBC Theses and Dissertations

The role of hospital toilets in microbial dissemination and the effectiveness of ultraviolet C irradiation Cooper, Jesse


Introduction: Healthcare-associated infections are a significant public health burden, which affect thousands of Canadians and cost millions of dollars, annually. Flushing toilets can generate pathogen-containing droplets and aerosols, and are a unique challenge in controlling pathogen transmission in healthcare facilities and other settings. This research assessed microbial dissemination of a) bacteria and b) virus from a flushing toilet in a patient area at Vancouver General Hospital. This project also c) evaluated the effectiveness of a permanently installed, automated ultraviolet C (UVC) device for reducing bacterial concentrations in air and on two surfaces in a shared patient bathroom at Lions Gate Hospital. Methods: a) Gram negative Escherichia coli and Gram positive Enterococcus faecalis, were used to simulate human stool during flushing events and viable air samples were collected with the Duo Surface Air System 360 sampler at multiple locations and time points post-flushing. b) A norovirus surrogate, MS2 bacteriophage, was also used to assess potential aerosolization of norovirus during flushing. c) Airborne and surface bacterial concentrations were compared in a bathroom with UVC and a comparable control bathroom. Results: a) Gram negative E. coli concentrations exceeded E. faecalis immediately post-flush at the location closest to the source, but decreased rapidly at successive time points and further sampling locations. In contrast, the Gram positive E. faecalis persisted significantly longer, and sampling location had no effect on its concentrations. b) Airborne phage was detected at concentrations far above the infectious dose for norovirus of 18 virions, and infectious phage particles were still present up to 60-minutes post-flushing. c) Airborne and surface bacterial concentrations were significantly reduced in the bathroom with UVC, compared to a comparable control bathroom. Conclusion: This work was the first study to evaluate both a Gram negative and Gram positive organism in the toilet plume, and show significantly longer persistence of the Gram positive bacteria. This research also showed that flushing toilets may generate airborne norovirus at concentrations capable of causing infection. Lastly, this work showed that optimized UVC is an effective adjunct to manual cleaning and infection control efforts in bathrooms.

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