Key points
- Up to 90 per cent of antibiotics taken are passed through our bodies into toilets and enter sewage systems, ultimately reaching wastewater treatment plants.
- Wastewater treatment plants act as 'hidden reservoirs' of bioactivity, with both antibiotics and their by-products contributing to antibiotic resistance.
- The chemical compounds that are formed when antibiotics degrade can drive as much resistance as the original drug.
Antibiotics continue to drive antimicrobial resistance in bacteria even after passing through wastewater treatment plants and being discharged into rivers and seas, research has found.
Researchers from The University of Queensland and University of Exeter found antibiotic transformation products - the chemical compounds that are formed when antibiotics degrade - can drive as much resistance as the original drug.
UQ PhD candidate Pooja Lakhey said up to 90 per cent of antibiotics taken are passed through our bodies into toilets and enter sewage systems, ultimately reaching wastewater treatment plants.
"Antibiotic resistance is a major global health threat, labelled the 'silent pandemic' that already contributes to 5 million deaths a year,'' Ms Lakhey said.
"Wastewater treatment is widely considered to reduce antibiotic concentrations and biological activity, although not necessarily eliminate them.
"Our research shows wastewater treatment plants can act as hidden reservoirs of bioactivity, with both antibiotics and their by-products contributing to resistance.
"In some cases, the breakdown products triggered resistance at the same exposure level as the original antibiotics, suggesting that even after antibiotics degrade, they can retain the ability to promote antibiotic resistance in bacteria.''
Antibiotic resistance - the ability of bacteria to survive drug treatments - can lead to inability to treat infections.
Wastewater samples collected from Queensland and Cornwall in England, showed bacteria developed resistance when exposed to antibiotic breakdown products from 3 classes of antibiotics.
Previous UQ research measured the concentration of about 100 antimicrobial agents and their transformation products in 50 wastewater treatment plants across Australia, finding high concentrations in water systems.
It also identified some sites with effective removal of these compounds, indicating wastewater treatment plants may be able to help solve the problem.
Dr Jake O'Brien from UQ's Queensland Alliance for Environmental Health Sciences said antibiotics and their breakdown products were not commonly tested in wastewater or environmental monitoring programs.
"Water utilities are not the reason for antimicrobial resistance but unfortunately are stuck dealing with whatever happens to get flushed,'' Dr O'Brien said.
"They are pivotal for giving us samples and many are interested in trying to deal with problems once we've identified them.
"The real issues are that humans use too many antibiotics and their breakdown products continue to drive antibiotic resistance.''
University of Exeter researcher Dr Aimee Murray said there was an urgent need to reduce the number of resistant bacteria in waterways to minimise people's exposure and risk.
"We are recommending risk assessment which takes into account the impact of both the original chemical, such as an antibiotic, and the component parts into which it breaks down through treatment,'' Dr Murray said.
"We need to move towards treatment processes which can reduce the danger of all these elements in driving resistance."
Read the research in Nature Water.
Collaboration and acknowledgements
The research was conducted in collaboration with University of Exeter.
