Sink Drains Were the Reservoir of a Prolonged ICU Pseudomonas Outbreak. Disinfecting the Drains Stopped It.
Key takeaway.
During a prolonged outbreak of multidrug-resistant Pseudomonas aeruginosa in a Dutch ICU, contaminated sink drains were the environmental reservoir. Fitting the sink siphons with a disinfection device cut drain colonization from 51% to 5% and reduced new patient acquisition to zero, confirming that the drain was driving transmission.
The study.
Researchers at Leiden University Medical Centre in the Netherlands investigated a prolonged outbreak of multidrug-resistant Pseudomonas aeruginosa across two intensive care subunits. Sampling of sink drains and patients over time identified the sink siphons as the persistent environmental reservoir feeding the outbreak.
In a before-and-after design, the team fitted the sink siphons with a disinfection device that applies heat and electromechanical vibration to the draining fluid, then tracked both drain colonization and new patient acquisition. Molecular typing confirmed that the environmental and clinical isolates were the same strain.
After the devices were installed, sink-drain colonization dropped sharply and new patient colonizations fell to zero. Where drains were left untreated, colonization rose, then fell once the devices were fitted there too, confirming that interrupting the drain reservoir interrupted transmission.
Key findings.
- Sink drains were the outbreak reservoir Molecular typing tied the multidrug-resistant Pseudomonas aeruginosa colonizing the sink drains to the patient isolates, identifying the sink siphon as the environmental source of the prolonged outbreak.
- Drain colonization fell from 51% to 5% In ICU subunit A, sink-drain colonization dropped from 51% at baseline to 5% after the disinfection device was fitted to the siphons (P < 0.001).
- New patient acquisition fell to zero New patient colonization dropped from 8.3 to 0 per 1,000 admissions in subunit A, and from 2.7 to 0.5 per 1,000 admissions in subunit B.
- Untreated drains got worse In the subunit left untreated for a period, drain colonization rose from 46% to 62%, then fell to a few percent only after the disinfection devices were installed there as well.
What this means for your facility.
This study is direct evidence that sink drains can be the hidden engine of a resistant-organism outbreak, and that acting on the drain itself, not just the patients, is what interrupts transmission. The same standing-water trap environment exists in the floor drains found throughout commercial, food-service, and healthcare facilities.
The de Jonge team controlled their outbreak with an active disinfection device fitted to every siphon, which requires equipment, power, and ongoing operation. A waterless trap seal addresses the same reservoir problem passively: Green Drain's one-way silicone valve removes the standing water a conventional water trap relies on and closes the drain when it is not in use, restricting the upward movement of air and aerosols. Independent SGS testing (Report QDF25-0049810-01) found the GD3 retained over 99.9% of an aerosolized viral surrogate (MS2 bacteriophage) in a controlled bench test.
Green Drain does not manage outbreaks and this study did not test a trap seal. But its central finding, that the drain reservoir has to be addressed to stop transmission, is exactly why a reliable drain barrier belongs in a preventive maintenance program rather than a reactive one.
Full citation.
Related research.
Protect your facility's drains.
Green Drain's waterless trap seal is a supportive engineering control that restricts the upward movement of air and aerosols, backed by independent bench testing. See how it works for your industry.