Fluid fragmentation from hospital toilets

2017

Healthcare-associated infections are a significant public health burden, which affect thousands of Canadians and cost millions of dollars, annually. Flushing toilets can generate pathogencontaining 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. iii 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.

International Journal of Infection Control, 2015

Although the relevance of surface disinfection is increasingly being accepted, there are still a number of issues which remain controversial. In hospital environments in Quebec (Canada), a three-step technique of cleaning and disinfection is used following a case of Clostridium difficile contamination. This technique brings together three factors: chemical, mechanical and microbiological. The present study investigates the impact of the mechanical action during each of these three-steps on C. difficile spore populations. Thus, cleaning and sporicidal products were replaced by water. The reduction rate of C. difficile spores was evaluated on four contaminated types of surfaces commonly found in the hospital environment. They included: ceramic, polyvinyl chloride (PVC), melamine and 2-methylprop-2-enoate methyl (PMAM) bed lining According to the type of the inert surface, variation in the reduction rate of spores was observed. The bed lining was the most difficult surface to clean, fo...

arXiv: Fluid Dynamics, 2020

Violent expiratory events, such as coughing and sneezing, are highly nontrivial examples of two-phase mixture of liquid droplets dispersed into an unsteady humid turbulent fluid phase. Understanding the physical mechanisms determining the fate of droplets is becoming a priority given the global COVID-19 emergency caused by the SARS-CoV-2 infection. By means of state-of-the-art fully resolved direct numerical simulations we contribute to solve this issue by identifying the key role of turbulence on the fate of exhaled droplets. Our results impact the current notion of social distance.

Antimicrobial Resistance & Infection Control, 2020

Background Pre-wetted disinfectant wipes are increasingly being used in healthcare facilities to help address the risk of healthcare associated infections (HAIs). However, HAIs are still a major problem in the US with Clostridioides difficile being the most common cause, leading to approximately 12,800 deaths annually in the US. An underexplored risk when using disinfectant wipes is that they may cross-contaminate uncontaminated surfaces during the wiping process. The objective of this study was to determine the cross-contamination risk that pre-wetted disinfectant towelettes may pose when challenged with C. difficile spores. We hypothesized that although the tested disinfectant wipes had no sporicidal claims, they will reduce spore loads. We also hypothesized that hydrogen peroxide disinfectant towelettes would present a lower cross-contamination risk than quaternary ammonium products. Methods We evaluated the risk of cross-contamination when disinfectant wipes are challenged with ...

Indoor Air, 2011

The droplets exhaled by an index patient with infectious disease such as influenza or Tuberculosis may be the carriers of contagious agents. Indoor environments such as the airliner cabins may be susceptible to infection from such airborne contagious agents. The present investigation computed the transport of the droplets exhaled by the index patient seated in the middle of a seven-row, twin-aisle, fully-occupied cabin using the CFD simulations. The droplets exhaled were from a single cough, a single breath and a 15-s talk of the index patient. The expiratory droplets were tracked by using Lagrangian method and their evaporation was modeled. It was found that the bulk airflow pattern in the cabin played the most important role on the droplet transport. The droplets were contained in the row before, at, and after the index patient within 30 s and dispersed uniformly to all the seven rows in 4 minutes. The total airborne droplet fraction reduced to 48%, 32%, 20%, and 12% after they entered the cabin for 1, 2, 3 and 4 minutes, respectively, due to the ventilation from the environmental control system.

American Journal of Infection Control, 2014

Background: The airborne spreading of enteric viruses can occur through the aerosol and droplets produced by toilet flushing. These can contaminate the surrounding environment, but few data exist to estimate the risk of exposure and infection. For this reason environmental monitoring of air and selected surfaces was carried out in 2 toilets of an office building and in 3 toilets of a hospital before and after cleaning operations. Methods: To reveal the presence of norovirus, enterovirus, rhinovirus, human rotavirus, and Torque teno virus and to quantify human adenovirus and bacteria counts, molecular and cultural methods were used. Results: On the whole, viruses were detected on 78% of surfaces and in 81% of aerosol. Among the researched viruses, only human adenovirus and Torque teno virus were found in both surface and air samples. In several cases the same adenovirus strain was concurrently found in all matrices. Bacterial counts were unrelated to viral presence and cleaning did not seem to substantially reduce contamination. Conclusions: The data collected in our study confirm that toilets are an important source of viral contamination, mainly in health care settings, where disinfection can have a crucial role in preventing virus spread.

2012

PLOS ONE, 2017

The WHO Consensus Document on the epidemiology of the SARS epidemic in 2003, included a report on a concentrated outbreak in one Hong Kong housing block which was considered a 'super-spreading event'. The WHO report conjectured that the sanitary plumbing system was one transmission route for the virus. Empty U-traps allowed the aerosolised virus to enter households from the sewerage system. No biological evidence was presented. This research reports evidence that pathogens can be aerosolised and transported on airstreams within sanitary plumbing systems and enter buildings via empty U-traps. A sanitary plumbing system was built, representing two floors of a building, with simulated toilet flushes on the lower floor and a sterile chamber with extractor fan on the floor above. Cultures of a model organism, Pseudomonas putida at 10 6-10 9 cfu ml-1 in 0Á85% NaCl were flushed into the system in volumes of 6 to 20 litres to represent single or multiple toilet flushes. Air and surface samples were cultured on agar plates and assessed qualitatively and semi-quantitatively. Flushing from a toilet into a sanitary plumbing system generated enough turbulence to aerosolise pathogens. Typical sanitary plumbing system airflows (between 20-30 ls-1) were sufficient to carry aerosolised pathogens between different floors of a building. Empty U-traps allowed aerosolised pathogens to enter the chamber, encouraging cross-transmission. All parts of the system were found to be contaminated post-flush. Empty U-traps have been observed in many buildings and a risk assessment indicates the potential for high risk cross-transmission under defect conditions in buildings with high pathogen loading such as hospitals. Under defective conditions (which are not uncommon) aerosolised pathogens can be carried on the airflows within sanitary plumbing systems. Our findings show that greater consideration should be given to this mode of pathogen transmission.

Applied and Environmental Microbiology

There have been an increasing number of reports implicating Gammaproteobacteria as often carrying genes of drug resistance from colonized sink traps to vulnerable hospitalized patients. However, the mechanism of transmission from the wastewater of the sink P-trap to patients remains poorly understood. Herein we report the use of a designated hand-washing sink lab gallery to model dispersion of green fluorescent protein (GFP)-expressing Escherichia coli from sink wastewater to the surrounding environment. We found no dispersion of GFP-expressing E. coli directly from the P-trap to the sink basin or surrounding countertop with coincident water flow from a faucet. However, when the GFP-expressing E. coli cells were allowed to mature in the P-trap under conditions similar to those in a hospital environment, a GFP-expressing E. coli -containing putative biofilm extended upward over 7 days to reach the strainer. This subsequently resulted in droplet dispersion to the surrounding areas (&l...