Drug-Resistant Citrobacter Circulated in Hospital Drains for Five Years
Key takeaway.
Carbapenem-resistant Citrobacter freundii persisted in hospital shower drains for five years despite daily cleaning and intermittent disinfection. Whole-genome sequencing linked the dominant clone to 12 patients and 8 environmental samples across four years, proving long-term plumbing-to-patient transmission.
The study.
Researchers at Ghent University Hospital in Belgium documented multiple sequential outbreaks of carbapenemase-producing Citrobacter freundii on the geriatric ward from 2017 to 2022. Environmental screening of toilet water, sink drains, and shower drains was conducted alongside clinical isolate collection from 30 patients over the five-year period.
The investigation revealed that sanitary plumbing installations - particularly shower drains and toilet water - acted as persistent reservoirs for pathogenic bacteria despite daily cleaning protocols and intermittent disinfection. Shower drains showed the highest contamination rate at 38.2% of samples, followed by toilet water at 25.0%, while sink drains showed 3.3% positivity.
Whole-genome sequencing identified three distinct patient-derived clusters, with the largest (ST22) connecting 12 patients and 8 environmental isolates across four years. This demonstrated long-term circulation and transmission of clones through the hospital's wastewater system, with biofilm formation enabling bacterial persistence despite active surveillance and infection prevention efforts.
Key findings.
- Shower drains most contaminated at 38.2% Environmental screening found CPE in 19.0% of all samples (73/385), with shower drains most contaminated (38.2%), followed by toilet water (25.0%) and sink drains (3.3%).
- Dominant clone persisted for four years The ST22 Citrobacter freundii cluster survived from 2018 through 2021 across patient and environmental samples, indicating biofilm-mediated long-term survival in plumbing.
- Daily cleaning failed to eliminate pathogens Standard daily cleaning and intermittent disinfection protocols failed to eradicate the pathogenic clones, demonstrating the inadequacy of conventional decontamination for entrenched drain biofilms.
- Genetic match between drains and patients Environmental isolates matched patient isolates at the genomic level, establishing a clear epidemiological link between plumbing biofilms and healthcare-associated infections.
What this means for your facility.
This study is a five-year case study of what happens when drain biofilms go uncontrolled. Daily cleaning and intermittent disinfection - the standard of care at a major university hospital - could not eliminate the reservoir. The same biofilm colonization dynamics exist in every water-filled drain trap: standing water, low flow velocity, and nutrient-rich wastewater create the conditions for persistent bacterial communities.
Green Drain's waterless silicone valve design prevents biofilm formation in drain traps by eliminating the standing water where these communities establish. Rather than attempting to maintain and disinfect standing water that inevitably becomes recolonized, Green Drain removes the aqueous environment entirely. This is a fundamentally different approach from the repeated disinfection cycles that Hamerlinck and colleagues documented failing over five years.
For facilities with geriatric, oncology, or transplant populations, the implications are clear. Drain biofilms represent a persistent transmission pathway that routine cleaning cannot address. Green Drain's drop-in installation provides a structural solution that eliminates the drain component of this vulnerability without disrupting clinical operations or requiring ongoing chemical treatment protocols.
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