This September, NASA and ROSCOSMOS went back and forth over the cause of a leak at the International Space Station, though they may have been better served by directing their attention to the station’s toilets and exercise platforms. On Thursday, scientists reported that in those hard-to-reach, often grimy places, a different threat has been brewing.

It’s no secret, of course, that microbes inhabit the ISS. In fact, NASA tracks the communities that emerge in the station’s dust particles. But recently, scientists publishing in BMC Microbiology analyzed the genomes of five specific ISS microbes (in this case, drawn from an exercise platform and the ISS toilet in 2015) to see what they might be genetically capable of. The five strains, they report, share similarities with three strains on earth, all which all belong to one species: Enterobacter bugandensis.

This identification yields both good and bad news.

ISS
The ISS in March 2009. 

The microbes appear not to be pathogenic to humans — at least right now. But they they may pose serious issues in the future because they also appear to have the genes required for resisting antibiotics, which are our only way of dealing with infection. When passed from microbe to microbe — and this can happen “horizontally” among bacteria, without sexual reproduction — these same genes can create superbugs here on Earth.

The terrestrial version of E. bugandensis is already known to cause life-threatening infections in infants and some adults with immune system complications. Fortunately for astronauts, the microbes aboard the ISS have slightly different genomes that make it non-virulent toward humans. However, lead study author Kasthuri Venkateswaran, Ph.D., a research scientist at NASA’s Jet Propulsion Laboratory, is wary that the bugs might eventually develop this ability, so NASA’s scientists will be watching them closely in the future.

“Whether or not an opportunistic pathogen like E. bugandensis causes disease and how much of a threat it is, depends on a variety of factors, including environmental ones.” Venkateswaran said, “Further in vivo studies are needed to discern the impact that conditions on the ISS, such as microgravity, other space, and spacecraft-related factors, may have on pathogenicity and virulence,” he added.

Another alarming point made in this paper is that the ISS version of E. bugandensis could have the genes for antibacterial resistance, which is already wreaking havoc on Earth. The paper suggests that the strains aboard the ISS have genes that render “broad spectrum resistance,” which means that the strains are equipped with a variety of genetic tools that might help them resist more than one type of drug.

Space agencies will have to take this potential danger into consideration as they plan future journeys for the tight, enclosed system that is the ISS, adds NASA’s Nitin Singh, Ph.D., the paper’s first author.

“Given the multi-drug resistance results for these ISS E. bugandensis genomes and the increased chance of pathogenicity we have identified,” says Singh, “these species potentially pose important health considerations for future missions.”