News Feature | February 19, 2016

Sewage Treatment Seen As Barrier To Rising Antibiotic Resistance

Sara Jerome

By Sara Jerome,

Scientists are finding an increasing number of bacteria resistant to antibiotics in waterways in the U.S. and around the globe. But a growing body of research shows that effective wastewater treatment can help curb the threat.

Researchers at the National University of Ireland are studying the role of effective wastewater treatment in combating antibiotic-resistant bacteria. In a study published last month by the Irish Environmental Protection Agency, researchers examined sewage from hospitals and from cities.

“High levels of resistant bacteria existed in hospital sewage where — on average — one in three patients are on antibiotics. Bacteria in hospital sewage also proved resistant to a number of ‘newer’ antibiotics,” the Connacht Tribune reported.

The research examined the role of wastewater treatment in fighting the problem.

“The study showed resistant bacteria was reduced greatly by effective wastewater treatment. However, [the researchers] maintain that it did not eliminate them completely. Some antibiotic resistant bacteria survive and are discharged to seawater,” the news report said.

“Urban wastewater and sewage treatment is vitally important in combating the global phenomenon of antibiotic and antimicrobial resistance. Untreated sewage has a long term ecological impact on the environment,” the news report said.

Which treatments are effective? The study named a few:

[Previous research] showed that advanced methods for treatment of hospital wastewaters, such as by reverse osmosis, using activated carbon or by ozonation, reduce or eliminate antimicrobials. Reducing sludge spreading is another possible method for decreasing the level of antimicrobials entering the waterways. [Previous research has] credited oxidation with ozone or chlorine species as having the highest capacity for the removal of antimicrobial agents from surface and spiked distilled waters. These authors also identified that minimal antimicrobial removal occurs through coagulation, flocculation, sedimentation or excess lime softening, a chemical process that converts calcium and magnesium in water to calcium carbonate and magnesium hydroxide.

Dearbháile Morris, a bacteriologist who worked on the study, weighed in on the findings.

“Our work shows that there is a risk related to antibiotics and antibiotic resistant bacteria in sewage but that a high standard of sewage treatment goes a long way to reduce that risk,” she said, per the report. “This is one more reason why the discharge of untreated or inadequately treated sewage to the environment in Ireland or indeed anywhere in Europe or the wider world is an unacceptable risk to our health.”

A new study from researchers at the University of Georgia also underscored the extent of the problem. Recent research published in the journal Environmental Microbiology drew on samples from 11 locations on nine streams. The researchers tested a panel of five antibiotics on 427 E. coli strains found in the streams.

“The results revealed high levels of antibiotic resistance in eight of the 11 water samples. The highest levels were found at the northern location of Upper Three Runs Creek, where the stream system enters the site, and on two tributaries located in the industrial area. The level of antibiotic resistance was high in both water and sediment samples from these streams,” the University of Georgia said in a statement.

A project at the University of Colorado is also working to expose the threat of antibiotic resistant bacteria.

“Students are tasked with collecting a small water sample from area water sources. Those samples are then tested for bacteria, to determine what antibiotic resistant strains are present. Antibiotic resistance occurs when bacteria survives a chemical that typically kills that species,” The Denver Channel reported.

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