Hospital sewer systems may be contributing to the spread of dangerous antibiotic-resistant bacteria, according to a new study published in the journal Nature Communications.
The research, conducted by scientists in Sweden, found that wastewater from hospitals created conditions that encouraged the growth of resistant bacteria, a phenomenon not observed in municipal wastewater.
Antibiotic resistance occurs when bacteria evolve to survive medications designed to kill them, making infections more difficult to treat. In the U.S. alone, over 9.3 million drug-resistant infections occur annually, leading to more than 39,000 deaths, according to the CDC.
How Hospital Wastewater Fosters Resistance
Researchers analyzed wastewater from 10 hospitals and eight municipal treatment plants to determine if hospital wastewater actively promoted the development of resistant bacteria. In laboratory experiments, filtered hospital wastewater significantly aided the growth of E. coli strains resistant to ciprofloxacin and cefotaxime, two common antibiotics.
In contrast, none of the municipal wastewater samples exhibited this effect. Further investigation involved placing plastic plates in sewer pipes. After 30 days, bacteria growing on these surfaces within hospital sewer pipes were approximately three times more likely to be resistant to the tested antibiotics compared to bacteria in the surrounding wastewater. This pattern was not observed in municipal sewers.
The study also measured antibiotic levels in the wastewater, identifying ciprofloxacin as a significant factor in promoting resistance, with cefotaxime also playing a role.
"The discovery [suggests] that hospital sewers could be a spawning 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 Centre for Antibiotic Resistance Research, told Fox News Digital. "Knowing where resistant bacteria are promoted — and where they are less likely to be — is crucial when deciding how resources and efforts should be allocated to limit risks for antibiotic resistance development."
Limitations and Potential Pathways
The study acknowledged several limitations, including that all sampling occurred in Sweden and focused on specific bacteria and antibiotics. The findings may not be universally applicable to all bacteria or geographical locations. The sewer pipe experiment lasted 30 days, leaving longer-term effects uncertain, and the study did not directly link hospital wastewater to increased infections in patients or surrounding communities.
However, Larsson suggested that resistant bacteria could potentially reach the public through contaminated water, particularly during heavy rainfall when wastewater treatment plants can become overloaded and release untreated or partially treated water.
"If people get in contact with such waters, they can acquire those bacteria and then continue spreading them from person to person," Larsson explained. The extent to which exposure leads to colonization or infection remains unclear.
Strategies for Prevention
The researchers proposed two main strategies to mitigate antibiotic resistance in hospital wastewater. One approach involves using alternative antibiotics that are less likely to persist in patients' bodies and promote resistance in wastewater, though the medical needs of patients must remain the priority. The second strategy focuses on treating wastewater directly at hospitals to remove resistance-promoting antibiotics, such as fluoroquinolones and beta-lactams, along with harmful bacteria.
Treating wastewater at municipal plants was deemed less effective because antibiotic concentrations are already high enough to favor resistant bacteria. While existing technologies can remove antibiotics from wastewater, they can be costly and require additional treatment. Larsson expressed optimism that a better understanding of the drivers of resistance could lead to more targeted and cost-effective technical solutions.