Automated Decontamination of Multiple Washbasin U-bends in a Hospital Setting Using Electrochemically Activated Solutions: Exploring the Role U-bends and the Wastewater Network Plays in the Trafficking of Potentially Pathogenic Bacteria in a Healthcare Facility
Citation:
MOLONEY, ELAINE MARY, Automated Decontamination of Multiple Washbasin U-bends in a Hospital Setting Using Electrochemically Activated Solutions: Exploring the Role U-bends and the Wastewater Network Plays in the Trafficking of Potentially Pathogenic Bacteria in a Healthcare Facility, Trinity College Dublin.School of Dental Sciences, 2020Download Item:
Abstract:
Hand washing is a vital component of any hand hygiene strategy, essential for reducing nosocomial infections. Paradoxically, hand washbasins have been identified as reservoirs and disseminators of infection. Washbasin U-bends are pipe fixtures located directly below the drain outlet designed to retain water that acts as a seal preventing gases entering buildings from wastewater pipes. However, frequently stagnation of this water facilitates biofilm formation. All previous approaches to decontaminating U-bends have been ineffective in the long-term, potentially hazardous to staff, toxic to the environment and/or incur high running costs.
The primary aim of this thesis was to develop an automated system for simultaneously decontaminating multiple washbasin U-bends and associated proximal wastewater pipes in the Dublin Dental University Hospital (DDUH) Accident & Emergency Department (A&E) by sequential treatment with electrochemically activated solutions (ECAs) generated from brine. A programmable system was developed whereby 10 identical washbasins, U-bends and associated pipework underwent automated sequential 10 min treatments with two ECAs. Catholyte, predominantly composed of sodium hydroxide, was used first to disrupt and loosen organic material. Anolyte, predominantly composed of hypochlorous acid, was then used to decontaminate washbasin pipework. A valve incorporated downstream of the U-bends permitted retro-filling and retention of the solutions. Six untreated washbasins with identical U-bends were selected as controls. This initial phase of the study investigated the efficacy of the ECA decontamination approach on the bacterial bioburden in A&E U-bends, monitored over a period 5 months and 62 decontamination cycles. Bacterial counts in U-bends were determined by swab sampling of the U-bends and the counts were recorded on Columbia blood agar, Reasoner?s 2A agar and Pseudomonas aeruginosa selective agar. Average counts from treated U-bends relative to controls showed a >3 log difference and was highly significant (P <0.0001). Pseudomonas aeruginosa predominated in all U-bends sampled. The next phase of research investigated the efficacy of this approach over a longer period (52 weeks and 156 decontamination cycles) using 10 identical washbasins and U-bends to those in A&E located in DDUH Clinic 2 as controls. The average counts from the 10 ECA-treated A&E U-bends following treatment relative to the 10 control U-bends showed a >3.3 log reduction on all three media. These results showed that ECA treatment of U-bends was consistently effective at minimising bacterial contamination in the long-term.
The second aim of this thesis was to investigate the bacterial communities present in washbasin U-bends and the associated wastewater pipe network in DDUH by laboratory culture and matrix-assisted laser desorption ionization time-of-flight mass spectrometry for isolate identification and by culture-independent Illumina 16S rRNA gene sequencing. Representative colonies, based on colony morphology, were recovered from the 10 ECA-treated A&E U-bends over a five-week period and from 10 non-treated Clinic 2 U-bends over two time points. Laboratory culture showed that P. aeruginosa predominated in treated and control U-bends. Illumina 16S rRNA gene sequencing analysis of the bacterial communities in non-treated U-bends and wastewater pipe locations identified a median number of 421 genera (range 291?573) per sample. The family Pseudomonadaceae and the genus Pseudomonas were identified in all 16 locations sampled, with the latter accounting for >10% of the relative genera in 5/16 samples. These data showed that sequence-based approaches reveal the presence of more diverse bacterial populations within the wastewater network than culture-based approaches.
The third aim of the thesis was to investigate trafficking of potentially pathogenic bacteria via U-bends and the wastewater pipe network in DDUH using Pseudomonas aeruginosa was used as a marker organism. The relatedness of isolates was investigated by whole genome sequencing and subsequent single nucleotide variant and whole genome multi-locus sequencing typing analyses. A total of 99 P. aeruginosa isolates were investigated from 25 U-bends in five locations and two wastewater pipe locations in DDUH. Eleven sequence types (STs) were identified, of which ST560 (n = 27; collected May 2017?May 2019) and ST179 (n = 34; collected January 2017?November 2019) predominated. Isolates within each of these STs were highly related regardless of source. Washbasin tap samples (n = 80) and mains and washbasin tap water samples (n = 72) failed to yield P. aeruginosa whereas P. aeruginosa was recovered from all DDUH U-bends investigated at some time point. These findings identified closely related P. aeruginosa isolates in multiple U-bends and wastewater pipes in diverse locations in DDUH and indicated that these were most likely spread by trafficking via the wastewater network.
This work highlights the role washbasin U-bends play in the spread of potential pathogens in a hospital wastewater network and emphasises the need for effective decontamination approaches. The automated U-bend ECA treatment system developed in the present study study provides a consistently effective approach.
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DDUH Microbiology Research Unit
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https://tcdlocalportal.tcd.ie/pls/EnterApex/f?p=800:71:0::::P71_USERNAME:EMOLONEYDescription:
APPROVED
Author: MOLONEY, ELAINE MARY
Advisor:
Coleman, David CPublisher:
Trinity College Dublin. School of Dental Sciences. Discipline of Dental ScienceType of material:
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Wastewater, Hand washing, U-bends, Decontamination, WashbasinsMetadata
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