Flying: Researchers find dangerous bacterial mixtures in airplane toilets

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Pathogens against which antibiotics no longer work are becoming an ever greater danger. The toilet in the plane may contribute to the spread. In one study, researchers found a large number of multi-resistant bacteria.

"The threat of antibiotic resistance has never been more immediate and the need for solutions more urgent," warned the head of the World Health Organization [WHO] recently. This is dangerous because there are too few new antibiotics on the market to circumvent this problem, said Tedros Adhanom Ghebreyesus. And that also has to do with aviation.

A recent study suggests that wastewater from aircraft toilets contributes to the threat. Researchers from various German and international universities took samples at five German airports. The investigation does not give the names of the airports. Based on the passenger numbers mentioned, however, it is clear that the three largest were there, with Frankfurt, Munich and Düsseldorf.

Resistance to three or more antibiotics

The samples were taken from the vehicles into which aircraft waste water is pumped out. "Since the tanks of the aircraft are only emptied when necessary, each contains waste water from several flights," says the study. The scientists examined the samples for antibiotic-resistant bacteria and resistance genes. For comparison, they used corresponding values ​​from German wastewater treatment plants with and without an airport connection. The result: On average, the samples from the aircraft showed significantly more and more diverse resistances.

Two particularly clear examples: Almost 90 percent of avian coli bacteria were resistant to at least one of the antibiotics tested. In the municipal sewage treatment plants, the values ​​were only between 45 and 60 percent. The proportion of multiple resistance to three or more antibiotics was also significantly higher than the comparison values. In a certain combination, the value from the aircraft wastewater even exceeded the value from German hospitals by a multiple.

Wastewater tanks need to be better researched

As a plausible explanation for the results, the study cites the mixing of intestinal bacteria from people from different regions of the world that occurs through the aircraft wastewater. However, the authors emphasize that other factors may also be decisive, but which have not yet been researched. For example, it is conceivable that certain disinfectants, which are often used in the waste water tanks of aircraft, create an environment that favors the development of certain resistances.

The scientists summarize: "Our results suggest that aircraft wastewater can effectively contribute to the rapid and global spread of antibiotic resistance." They continue to say that the aircraft wastewater is mixed with other wastewater and is thus quasi-diluted.

Treat waste water first, then mix

However, even the smallest amount of resistance genes in the water cycle could be dangerous. From this point of view, the problem is not so much the high number of resistance genes, but rather that genes are imported from the other end of the world into a local ecosystem, where they have so far hardly been found. The same applies to the multiple resistance to several antibiotics.

As a consequence of their findings, the scientists make two suggestions. On the one hand, they advise researching the processes in the waste water tanks. On the other hand, they recommend pretreating the airport waste water in the fight against resistance before it is mixed with municipal waste water. With the comparatively small amount, this is probably cheaper and more effective than worrying about the problem later.

No immediate health risk

Incidentally, the researchers in this study did not deal with germs in the toilets of the aviators. For passengers, the knowledge of resistance does not mean an immediate health hazard – unless maybe someone reaches directly into the toilet.

This article was written by Timo Nowack