A plane’s dirty little secrets

Most of us under­standably give little thought to what happens when we press the “flush” button on an airplane toilet. But for DTU Professor Frank Møller Aarestrup, the contents are a mine of information on the origin and spread of pathogens and antimicrobial resistance. He attracted worldwide headlines last summer when he presented his results on DNA analyses of toilet waste from international flights, and now believes such analyses should be conducted routinely.

“I was surprised to find how easy and affordable this approach was,” says Aarestrup. Using novel techniques for DNA sequencing, he has been able to reveal a genetic signature for virtually every microbe and resistance gene in the samples.

Generally, surveillance of infectious diseases is based on growing and identifying clinical isolates from patients at local diagnostic laboratories. The results must then be shared and evaluated, first at a national and then an international level. “This process can take years, and the data are unstructured and unstandardised,” says Aarestrup. “DNA sequencing, on the other hand, offers a standardised way to gather and compare data, and it is extremely easy to share over the Internet.”

Back in 2011, Aarestrup and his colleagues succeeded in tracing the Haitian cholera outbreak to Nepalese UN soldiers. “Unfortunately, this tracking did not help anyone, it was too late,” says Aarestrup. The technology is much more helpful when it is used to monitor the spread of infections while it actually happens. “This has been implemented for food-borne pathogens by the FDA and CDC in the U.S. and there it has made a difference in enabling targeted interventions.”

Going one step further, Aarestrup wants to step away from looking only at patients. “We want to monitor large, clinically healthy populations and get a truer overview of the occurrence of antimicrobial resistance and pathogens,” he explains. That was the rationale behind the plane-poo analysis, a line of research that will now be expanded to sewage.

Aarestrup has calculated that if DNA sequencing can be performed locally, it will be possible to analyze 1,000 sites once a week for around €2 million a year. “Mass screening of population hotspots could enable better knowledge of transmission routes as well as earlier detection of emerging problems”, he says. “Infectious diseases account for around 22% of all deaths worldwide. We should be able to cut this in half.”