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Hospital wastewater has been shown to promote the growth of antibiotic-resistant bacteria, potentially making sewer systems hot spots for antimicrobial resistance, according to a new Swedish study published in Nature Communications.
Antibiotics taken by patients can pass through their bodies and enter hospital sewer systems, creating conditions for the growth of resistant bacteria.
Antibiotic resistance occurs when bacteria develop the ability to survive drugs designed to kill them, making some infections more difficult to treat. More than 9.3 million drug-resistant infections occur each year in the United States, resulting in more than 39,000 deaths, according to the CDC’s 2026 Antimicrobial Resistance Threats Report.
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How hospital wastewater promotes antibiotic resistance
The researchers conducted a study of wastewater from 10 hospitals and eight municipal wastewater treatment plants.
They wanted to determine whether hospital wastewater actually promoted the growth of antibiotic-resistant bacteria, rather than simply carrying resistant bacteria from patients.
Hospital wastewater has been shown to promote the growth of antibiotic-resistant bacteria, potentially making sewer systems hot spots for antimicrobial resistance. (iStock)
First, the researchers filtered hospital wastewater to remove existing bacteria, then exposed other bacteria to the filtered water in laboratory experiments. All 10 hospital samples significantly promoted the growth of E. coli strains. coli resistant to ciprofloxacin and cefotaxime, two antibiotics used to treat bacterial infections.
None of the eight municipal wastewater samples showed the same effect.
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This suggests, researchers say, that something in the wastewater itself helps antibiotic-resistant bacteria thrive.
The team also placed plastic sheets in sewer pipes to study bacteria growing on their surfaces. After 30 days, bacteria growing on surfaces inside the pipes were about three times more likely to be resistant to both antibiotics than bacteria in the surrounding wastewater. This trend was not observed in municipal sewers.
The researchers conducted a study of wastewater from 10 hospitals and eight municipal wastewater treatment plants. (iStock)
The researchers also measured antibiotic levels in wastewater and tested whether those same concentrations helped resistant bacteria grow in laboratory experiments. They found that ciprofloxacin was a major contributor, while cefotaxime also played a role.
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“The finding (suggests) that hospital sewers could be a breeding ground for bacteria that are difficult to treat with antibiotics,” Joakim Larsson, professor of environmental pharmacology at the University of Gothenburg and director of the Center for Antibiotic Resistance Research, told Fox News Digital.
“Patients’ need for antibiotics must not be compromised.”
“Knowing where resistant bacteria are favored – and where they are less likely to be found – is crucial for deciding how resources and efforts should be allocated to limit the risks of developing antibiotic resistance.”
The study had several limitations. All sampling sites were in Sweden, and the researchers focused primarily on E. coli and a limited number of antibiotics. Therefore, results may not apply to all bacteria or locations.
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The sewer experiment lasted about 30 days, leaving the long-term effects uncertain. The study also did not determine whether the growth of resistant bacteria in hospital sewers leads to more infections in patients or surrounding communities.
Although the study did not establish a direct link between hospital wastewater and human infections, Larsson said resistant bacteria could potentially reach people through contaminated water.
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“When it rains a lot, sewage treatment plants are usually overloaded and discharge untreated or partially untreated sewage containing a lot of bacteria,” Larsson told Fox News Digital.
“If people come into contact with such waters, they can acquire these bacteria and continue to spread them from person to person,” he continued. “One thing that remains uncertain is how much exposure is necessary for resistant bacteria to colonize your gut or infect you.”
Preventing antibiotic resistance
Researchers have identified two possible approaches to reducing antibiotic resistance in hospital sewers.
The first is to use alternative antibiotics that are less likely to pass through patients’ bodies unchanged and that promote the growth of resistant bacteria in wastewater.
All 10 hospital samples significantly promoted the growth of E. coli strains. coli resistant to ciprofloxacin and cefotaxime, two antibiotics used to treat bacterial infections. (iStock)
“But – and this is an important but – patients’ need for antibiotics must not be compromised,” Larsson said, emphasizing that equally effective alternatives are not always available and that patients’ medical needs must come first.
The second approach involves treating hospital wastewater to remove antibiotics that promote resistance, particularly fluoroquinolones and beta-lactams (two classes of antibiotics used to treat bacterial infections), while also eliminating harmful bacteria.
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Larsson said wastewater treatment at municipal plants would likely be less effective because antibiotic concentrations are high enough to foster resistant bacteria, primarily in hospital sewers.
Existing technologies can remove antibiotics from wastewater, but they can be expensive and require additional treatment, he noted.
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“When we know more about the engines, we think it might be possible to develop targeted and hopefully less expensive technical solutions,” Larsson added.
Fox News Digital has contacted the American Hospital Association for comment.
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