Novel coating kyboshes ISS bacteria
Researchers report microbe numbers drop, but survivors are multi-drug-resistant. Andrew Masterson reports.
A novel antimicrobial coating deployed in the International Space Station could be the solution to the presence of most, but not all, bacterial colonies on board the craft.
The presence of bacteria inside the ISS has been the subject of a lot of research and considerable concern.
Where humans go, microbes always follow, and the ISS is no exception. However, the uniquely harsh microgravitational environment inside the station – and the presence of unfettered cosmic rays outside it – have prompted fears that usually benign species of onboard bacteria could potentially mutate into something more pathogenic.
The issue was first raised in late 2018 after five strains of Enterobacter were recovered from areas on board the ISS, including the gym and toilet areas.
Researchers found that all strains belonged to a single species E. bugandensis, and were similar only to very rare versions found on Earth. The scientists calculated that there was a 79% chance that one or more of them could become disease-causing given the appropriate circumstances.
Months later a second study largely discounted the possibility of the Enterobacter becoming more virulent, but also raised possibilities regarding two other bacterial species found onboard: Staphylococcus aureus and Bacillus cereus.
Analysis showed that the microbes were indeed changing – an inevitable evolutionary process no matter the environment – and that, so far at least, there was no indication that any emerging highly pathogenic strain would have a fitness advantage.
Nevertheless, the chance of microbes turning nasty, however unlikely, persists.
Now, researchers led by Lydia-Yasmin Sobisch from Germany’s Berlin University of Applied Sciences report that a surface coating comprising micro-galvanic elements of silver and ruthenium has been successful in substantially reducing the bacterial densities inside the ISS.
The researchers installed trial panels of the coating – which they call AGXX – as well as others made of silver, a noted antimicrobial, and, as controls, untreated stainless steel.
In a paper published in the journal Frontiers in Microbiology, Sobisch and colleagues report that the novel substance hosted much lower numbers of bacteria than the silver of the steel.
Indeed, at six months, the AGXX contained no microbes at all.
However, the scientists report, “microbial diversity increased with increasing exposure time on all three materials”. At 12 months, the coating hosted nine bacterial isolates, but that number dropped to just three at 19 months.
In line with earlier studies, the predominant species found on all surfaces came from the genera Staphylococcus, Bacillus and Enterococcus.
Perhaps worryingly, however, the team found that most “pathogenic isolates were multidrug resistant”.