A study by University of Gothenburg researchers published in Nature Communications demonstrates that hospital sewer systems actively promote antibiotic-resistant bacteria through patient-excreted drugs. Examining sewage from ten Swedish hospitals, scientists identified ciprofloxacin and cefotaxime as primary drivers enriching resistant Escherichia coli in sewer biofilms. In contrast, municipal wastewater showed no selection, underscoring the need for targeted interventions in hospital plumbing.
Evidence of resistance selection in hospital sewers
- ▪A study by University of Gothenburg researchers published in Nature Communications found that sterile-filtered sewage from ten Swedish hospitals selected for antibiotic-resistant Escherichia coli, whereas municipal sewage showed no selection.
- ▪University of Gothenburg professor Joakim Larsson stated that the study provides the first direct environmental field evidence in over 25 years linking pharmaceuticals excreted by humans to observed ecological effects.
- ▪No significant enrichment of antibiotic-resistant Escherichia coli was observed in biofilms or wastewater samples taken from municipal wastewater treatment plants in Sweden.
- ▪Antibiotic-resistant Escherichia coli were enriched in biofilms within hospital sewer pipes compared to wastewater, providing direct field evidence of in situ selection.
Antibiotic usage and concentrations in hospitals
- ▪Approximately one-third of Swedish hospital in-patients undergo antibiotic therapy at any given time, compared to about one in 300 individuals in the Swedish general population.
- ▪Antibiotics excreted by hospitalized patients create drug concentrations up to hundreds of micrograms per liter in hospital wastewater, compared to a few micrograms per liter in municipal wastewater.
Specific antibiotics driving resistance selection
- ▪Ciprofloxacin, a fluoroquinolone antibiotic commonly prescribed for urinary tract infections, was identified as a primary driver selecting for resistant Escherichia coli in hospital sewers.
- ▪Chemical analyses and bacterial cell experiments confirmed that fluoroquinolone resistance gave Escherichia coli strains a selective growth advantage in hospital wastewater.
- ▪Making a sensitive Escherichia coli strain resistant to penicillin-like antibiotics enabled it to grow effectively in hospital sewage where it otherwise could not.
- ▪Cefotaxime, a penicillin-like cephalosporin antibiotic used exclusively in hospitals, was identified as a key driver promoting resistant Escherichia coli in hospital sewage.
Targeted interventions to mitigate selection pressure
- ▪Identifying specific driving antibiotics allows public health authorities to prioritize resource allocation and targeted upstream interventions in hospital plumbing systems.
- ▪Researchers at the University of Gothenburg are developing targeted treatment methods for hospital sewers to mitigate antibiotic selection pressure at its source.
- ▪Advanced treatment at municipal facilities can reduce the spread of active pharmaceuticals but cannot reverse resistance evolution that has already occurred in upstream hospital sewers.
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