Sink Drains Sustained a Multi-Year Pseudomonas Outbreak. Weekly Acetic Acid Stopped It.
Key Takeaway
A prolonged outbreak of metallo-beta-lactamase-producing Pseudomonas aeruginosa was traced to hospital sink drains, where the organism was recovered from 12 drains across three wards and matched the patient isolates. Treating the drains with acetic acid once a week produced negative cultures and halted transmission, showing the sink drains were the reservoir sustaining the outbreak.
The Study
Stjarne Aspelund and colleagues investigated a prolonged nosocomial outbreak of metallo-beta-lactamase-producing Pseudomonas aeruginosa (Pae-MBL) that ran from 2008 to 2014 across three hospital wards in Sweden. The organism was identified in 12 sink drains, and strain typing confirmed that the clinical and environmental isolates were identical or closely related, implicating the sink drains as the reservoir.
The team treated Pae-MBL-positive sinks with 24% acetic acid once a week and monitored them with repeat cultures. In vitro, acetic acid eradicated Pae-MBL biofilms at a minimum biofilm eradication concentration of 0.75% (range 0.19-1.5%). Weekly treatment produced negative drain cultures and halted transmission, demonstrating that a simple drain decontamination method could break the outbreak.
Key Findings
Sink drains were the outbreak reservoir
Metallo-beta-lactamase-producing Pseudomonas aeruginosa was recovered from 12 sink drains across three wards; strain typing confirmed the environmental and clinical isolates were the same or closely related.
A multi-year outbreak (2008-2014)
The Pae-MBL outbreak affected 14 patients over roughly six years before the drain reservoir was addressed, showing how persistent a drain-based source can be.
Acetic acid eradicated the drain biofilm
In vitro, acetic acid eradicated Pae-MBL biofilms at a minimum biofilm eradication concentration of 0.75% (range 0.19-1.5%), well within the 24% solution used on the sinks.
Weekly treatment halted transmission
Treating positive sinks with 24% acetic acid once a week produced negative cultures and stopped transmission, confirming the drains as the source.
What This Means for Your Facility
This outbreak took six years and repeated conventional measures before it was resolved, and it was resolved only once the sink drains, the reservoir, were decontaminated. The persistence of a drain-based Pseudomonas source is the same risk that exists in the floor drains of commercial, food-service, and healthcare buildings.
The molecular match between the drain and patient isolates confirms what other studies in this research library have shown: sink drains are active reservoirs, not passive contamination sites, and the standing-water trap is the enabling environment.
Stjarne Aspelund's team controlled their outbreak with a weekly acetic acid protocol on every positive sink. A waterless trap seal takes a different, preventive approach to the same drain by removing the standing water a conventional trap relies on. This study did not test a trap seal, and a waterless trap seal does not remediate an existing biofilm; its central lesson, that the drain reservoir has to be addressed, is why a passive engineering control at the drain belongs in a preventive maintenance program as a complement to, not a replacement for, infection prevention. In the SGS aerosol-retention test (Report QDF25-0049810-01), the GD3 retained over 99.9% of an aerosolized MS2 bacteriophage viral surrogate in a controlled bench test; surrogate retention is not a measure of pathogen retention.
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Address the Drain Reservoir
Green Drain's waterless trap seals remove the standing water a conventional trap relies on and act as a waterless one-way valve that restricts the retrograde movement of air and aerosols from the drainage system; they do not remediate an existing biofilm. Use them as a supportive engineering control that complements, not replaces, your infection prevention program.
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