Aircraft lavatory wastewater from international flights can serve as an early-warning system for antimicrobial resistance, according to an Australian-led study that detected multiple high-priority pathogens and antibiotic resistance genes in samples from incoming planes.
Scientists from CSIRO, in partnership with Xiamen University, the University of South Australia and Michigan Technological University, analysed wastewater from toilets on 44 international flights arriving in Australia from nine countries. Using advanced molecular techniques, they identified nine high-priority pathogens and superbugs and profiled antibiotic resistance genes (ARGs).
Five of the nine superbugs were present in every sample, while a gene that confers resistance to last-resort antibiotics was found on 17 flights. That gene was not detected in Australia’s urban wastewater during the same period, suggesting its likely introduction via international travel.
“Aircraft wastewater captures microbial signatures from passengers across different continents, offering a non-invasive, cost-effective way to monitor threats like AMR,” Dr Ahmed said.
The study found notable geographic differences in ARG concentrations. “Flights from Asia, particularly India, showed higher concentrations of antibiotic resistance genes, compared to flights from Europe and the UK,” Prof Ashbolt said. Of the 44 flights, 18 originated from India, 14 from the UK, six from Germany and the remainder were single flights from France, the UAE, Türkiye, South Africa, Japan and Indonesia. Lead author Dr Yawen Liu said the disparities could reflect differences in antibiotic use, water sanitation, population density and public health policies across regions. “International travel is one of the major drivers of AMR spread,” said Dr Liu. “By monitoring aircraft wastewater, we can potentially detect and track antibiotic resistance genes before they become established in local environments.”
To test the reliability of the approach, researchers examined whether aircraft toilet disinfectants degrade genetic material. They found nucleic acids remained stable for up to 24 hours even in the presence of strong disinfectants.
Samples were collected during COVID-19 repatriation flights, which may have influenced passenger demographics, but the authors say the method can be adapted to routine travel. The work builds on CSIRO’s previous collaborations that detected SARS-CoV-2 in wastewater from long-haul flights during the pandemic.
“With AMR projected to cause more than 39 million deaths globally by 2050, the need for innovative surveillance tools is urgent,” Prof Ashbolt said. “Aircraft wastewater monitoring could complement existing public health systems, providing early warnings of emerging superbug threats.”
“This is a proof-of-concept with real-world potential,” Dr Ahmed said. “We now have the tools to turn aircraft toilets into an early-warning disease system to better manage public health.”
The findings are published in Microbiology Spectrum (Aircraft lavatory wastewater surveillance for movement of antimicrobial resistance genes: a proof-of-concept study; DOI: 10.1128/spectrum.00569-25).
