Antibacterial coating helps astronauts fight superbugs on ISS

Scientists have developed a novel antimicrobial coating that can prevent drug-resistant bacterial contaminations aboard the International Space Station (ISS), and help protect astronauts in their journey beyond the Moon and Mars.

Extreme spaceflight conditions can force these bacteria to toughen up, while simultaneously lowering the immune defenses of the stressed, isolated crew. These effects and the risk of infection grow with mission duration.

"Spaceflight can turn harmless bacteria into potential pathogens," said Elisabeth Grohmann of Beuth University of Applied Sciences Berlin in Germany.

"Just as stress hormones leave astronauts vulnerable to infection, the bacteria they carry become hardier -- developing thick protective coatings and resistance to antibiotics -- and more vigorous, multiplying and metabolising faster," said Grohmann.

To make matters worse, the genes responsible for these new traits can be readily shared among different species of bacteria, via direct contact or in the 'matrix' of slime they secrete.

To address this problem, researchers tested a new antimicrobial coating, AGXX, on a contamination-prone surface aboard the ISS: the toilet door.

"AGXX contains both silver and ruthenium, conditioned by a vitamin derivative, and it kills all kinds of bacteria as well as certain fungi, yeasts and viruses. The effects are similar to bleach -- except the coating is self-regenerating so it never gets used up," said Grohmann.

Silver on its own has been used since prehistory to prevent microbial growth. Today it is found in everything from socks to swimming pools -- which is perhaps why resistant bacteria have begun to emerge.

AGXX is one of the latest attempts to reinvigorate this ancient antimicrobial, researchers said.

"After six months exposure on the ISS, no bacteria were recovered from AGXX-coated surfaces," Grohmann said.

Even at 12 and 19 months, a total of just 12 bacteria was recovered -- a reduction of 80 per cent compared to bare steel. A regular silver coating tested for comparison had only a slight antimicrobial effect, reducing the number of bacteria by 30 per cent versus steel.

"Most importantly, no serious human pathogens were found on any surface. Thus, the infection risk for the ISS crew currently is low," said Grohmann.

Nevertheless, all bacterial isolates were able to form immunity-evading slimy coatings, and most were resistant to at least three antibiotics. They were also able to share the genes responsible.