By analyzing 44 flights originating from nine different countries, the study found five of the "high-priority" bugs present in the wastewater while also discerning that nucleic acids needed for detection survived for at least 24 hours even in the presence of strong disinfectants.
Human mortality ebbs and flows with history -- in both cause and quantity. For example, Yersinia pestis (otherwise known as the plague) killed upwards of 50 million people in the mid-1300s. Today only a few thousand contract the disease with just a fraction of those cases proving fatal. However, this medical history can also work in reverse as scientists try to understand what could be the major killer of humans in the future.
One of the most worrying examples are antimicrobial resistant (AMR) superbugs that, as their name suggests, includes bacteria, viruses, fungi, and parasites that no longer respond to antimicrobial treatments. Because these antibiotic drugs are central to modern medicine, the arrival of these superbugs fill some scientists and physicians with dread -- for good reason. Estimates suggest that AMR organisms could cause 40 to 50 million deaths by 2050, a higher fatality rate than cancer.
To prepare for this possible future, scientists need to both design new therapies that can circumvent these organisms' newly acquired, antimicrobial powers while also putting into place detection systems to catch possible AMR outbreaks. In a new study published in the journal Microbiology Spectrum, an international team of scientists from Australia, China, and the U.S. details how airplane toilets, specifically the wastewater from those toilets, could be central to catching possible outbreaks before they happen.
"International travel is one of the major drivers of AMR spread," Xiamen University's Yawen Liu, a visiting scientist to Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) and lead author of the study said in a press statement. "By monitoring aircraft wastewater, we can potentially detect and track antibiotic resistance genes before they become established in local environments."
In the study, the research team analyzed wastewater from 44 flights that arrived in Australia that originated from nine different countries. By using advanced molecular screening methods, Liu and her team examined the genetic structure of nine "high-priority" superbugs that could potentially be present in the samples. Amazingly, five of those nine bugs were found in all 44 samples with 17 of those samples containing resistance to "last-resort antibiotics," basically modern medicine's last line of defense against an AMR organism.
The study also confirmed that samples retained nucleic acids vital for superbug detection for at least 24 hours even in the presence of strong disinfectants, which are typically used in aircraft toilets. Antimicrobial resistance also varied geographically, with more resistance popping up from flights coming from Asia. Liu says these variations could be caused by the origin country's public health policies, water sanitation practices, population densities, and overall antibiotic use.
Analyzing aircraft wastewater is a proven method for detecting disease, especially since travel has been the main vector for many human ailments since time immemorial. Previous studies have analyzed how aircraft wastewater helped track the spread of Covid-19 variants, and in fact, the data wastewater collected for this new study came from repatriation flights to Australia during the pandemic.
"With AMR projected to cause more than 39 million deaths globally by 2050, the need for innovative surveillance tools is urgent," University of South Australia's Nicholas Ashbolt, a co-author of the study, said in a press statement. "Aircraft wastewater monitoring could complement existing public health systems, providing early warnings of emerging superbug threats."