ISS Astronauts Test New Antibacterial Coating on the Bathroom Door

Astronauts aboard the International Space Station (ISS) have to deal with hazards associated with living and working in an environment completely inhospitable to humans. If anything happens to the station’s thin skin, it could spell disaster for the crew. As if that’s not enough danger, bacteria become more pathogenic in space as human immune systems become less effective. Research headed by Elisabeth Grohmann of Beuth University of Applied Sciences Berlin shows that a new antimicrobial substance could eliminate bacteria on surfaces. Surfaces like the bathroom door.

It seems like a cruel joke, but the features of spaceflight that make bacteria stronger, like microgravity and radiation, also make human immune systems less effective at fighting infections. Bacteria in microgravity can develop protective coatings called biofilms, allowing them to stick to surfaces. Meanwhile, radiation increases the rate of mutation and can lead to the development of antibiotic resistance traits. Bacterial cells can then share those traits with other cells.

These superbugs are of particular concern aboard the ISS where crew members can be living in space for as long as a year. The researchers evaluated a new antimicrobial coating that integrates silver and ruthenium, which they call AGXX. The silver and ruthenium are conditioned as vitamin derivatives, so they kill all bacteria as well as some fungi, yeasts, and viruses. It has a similar effect to bleach, but the coating is self-regenerating.

Astronauts aboard the ISS tested AGXX on a particularly bacteria-prone surface: the bathroom door. After six months on the ISS, the door remained free of bacteria. At 12 and 19 months, astronauts were able to recover just 12 bacteria from samples of the door. That’s an 80 percent reduction from a bare steel surface as the control. A silver coating, which is commonly used to repel bacteria, only lowers bacteria colonization by about 30 percent.

The team speculates that the reduced effectiveness over time was not due to a breakdown of AGXX or more virulent bacteria. Instead, dust and dirt likely adhered to the door and made it less effective at killing bacteria.

It’s worth noting, the ISS crew didn’t detect any bacteria in testing that posed a serious risk to humans. However, many of the strains did exhibit antibiotic resistance and the ability to form biofilms, which help them evade human immune systems. Having systems like AGXX treatment in place to keep bacterial colonization at a minimum is an important part of keeping astronauts healthy in space.