Work

The role of air pressure transients on the spread of bacteria from wash-hand basin sink traps in hospital en-suite bathrooms: a laboratory-based pilot study

Year: 2025

Type: article

Abstract: BACKGROUND: There is growing evidence for the involvement of sink and wash-hand basin traps in the spread of hospital-acquired infections in clinical settings. This pilot study used a full-scale model of a hospital wash-hand basin and wastewater drainage system, typical in single-occupancy hospital bathrooms, to examine bacterial transmission from sink traps to wash-hand basins during drainage system air pressure surges. METHODS: Simulating real-world conditions in a laboratory, a 50-m pipe network was connected to the model en-suite bathroom. Air pressure surges were generated within the pipe connection to the sink trap containing Pseudomonas alloputida KT2440 as a safe model bacterium. Measurements were made of air pressure, aerosol levels, and viable bacterial counts of the sink appliance using contact plates. RESULTS: Positive air pressure surges allowed water from the sink trap containing P. alloputida KT2440 to enter the wash-hand basin. Positive air pressure surges generated aerosols above the sink trap strainer. The strainer became contaminated without visible water ingress. Aerosols formed even without visible water, indicating sub-strainer agitation. Bacteria from the sink trap spread to surfaces, with viable cells recovered. Pressure surges occur naturally and increase with activities such as drain jetting. CONCLUSIONS: For the first time, it was shown that air pressure surges in wastewater drainage systems can spread bacteria from contaminated sink traps to wash-hand basins, particularly via aerosols. This emphasizes the need for a re-examination of hospital wastewater drainage system design and maintenance in order to mitigate this mechanism of contamination.

Source: Journal of Hospital Infection

DOI: 10.1016/j.jhin.2025.07.026

Authors: M. Gormley, D.A. Kelly, D.P. Campbell, T.J. Aspray, T. Dight

Institutions: Heriot-Watt University, National Centre for the Replacement Refinement and Reduction of Animals in Research, University of Hertfordshire

Language: English

Topic: Infection Control in Healthcare

Subfield: Infectious Diseases

Field: Medicine

Domain: Health Sciences

SDGs: Good health and well-being, Clean water and sanitation

Open Access status: hybrid

Estimated APC paid: $4,000