Sink Traps Were the Source of an ICU Outbreak. Decontaminating Them Stopped It for a Year.
Key Takeaway
An ICU outbreak of OXA-48-producing Serratia marcescens was traced to the sink traps, where the outbreak clone was recovered from 2 sink outlets and 16 sink traps and matched the patient isolates. After the sinks were decontaminated and staff were engaged on infection control, no additional cases occurred for 12 months, even though some environmental contamination persisted, confirming the sink traps as the source of transmission.
The Study
Regev-Yochay and colleagues investigated an outbreak of OXA-48-producing carbapenemase-producing Enterobacteriaceae in a single 16-room intensive care unit at Sheba Medical Center, Israel, between January 2016 and May 2017. Of 32 cases, 81% were Serratia marcescens, and a single clone caused all but the first two cases. Molecular typing linked the patient isolates to the sink environment.
The outbreak clone was recovered from 2 sink outlets and 16 sink traps, identifying the sink traps as the environmental reservoir; a common factor among affected patients was the use of relatively large amounts of tap water at the sinks. After the sinks were decontaminated and staff engaged through education and stricter infection control, no additional cases were detected for 12 months, despite persistent environmental contamination.
Key Findings
Sink traps were the source
The outbreak clone was recovered from 2 sink outlets and 16 sink traps; molecular typing matched the environmental and patient isolates, naming the sink traps as the transmission source.
A single clone, mostly Serratia marcescens
Of 32 OXA-48 carbapenemase-producing cases detected over about 16 months, 81% were Serratia marcescens, and one clone caused all but the first two cases.
Tap-water use was a shared patient factor
Patients who acquired the organism shared the use of relatively large amounts of tap water at the contaminated sinks, connecting sink use to acquisition.
Sink decontamination held for 12 months
After sink decontamination plus staff engagement and stricter infection control, no additional cases occurred for a year, even though some environmental contamination persisted.
What This Means for Your Facility
This is one of the clearest sink-trap-as-source outbreak investigations in the literature: the outbreak clone was in the sink traps, it matched the patients, and addressing the sinks stopped transmission for a year. The same standing-water sink and floor-drain traps exist throughout commercial, food-service, and healthcare buildings.
Notably, transmission stopped for 12 months even though the environment was never fully sterilized, showing that the drain reservoir was central to this outbreak. A waterless trap seal is a supportive engineering control that acts on the same reservoir differently: it uses a one-way valve that removes the standing water a conventional trap relies on and restricts the upward movement of air and aerosols from the drainage system into the room when the drain is not in use. It does not remediate or remove an existing biofilm, and no study, including this one, has tested a trap-seal barrier against an infection endpoint. This study did not test a trap seal; separately, independent SGS bench testing (Report QDF25-0049810-01) measured the physical retention of an aerosolized MS2 bacteriophage surrogate, finding the GD3 retained over 99.9% of the surrogate in a controlled bench test. That figure describes surrogate retention in a controlled test, not retention of any pathogen or a reduction in infection risk.
For infection prevention teams managing carbapenemase-producing organisms, this study makes the case that the sink and drain reservoir has to be part of the plan, not an afterthought once an outbreak is already underway. A passive engineering control at the drain that restricts the upward movement of air and aerosols complements, and does not replace, infection prevention, and it belongs in a preventive maintenance program rather than a reactive one.
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