No place is safe from the scourge of superbugs, suggests a new study, not even from space. According to the study, samples of bacteria resistant to various antibiotics were found on the International Space Station (ISS). And while the bacteria may not have left the astronauts sick, the authors say it is quite likely they can.
The authors behind the study, published last week at BMC Microbiology, are primarily members of the NASA Jet Propulsion Laboratory, which is managed by the California Institute of Technology. The laboratory is the leading research center for NASA's robotic space and Earth science missions, such as the Mars Curiosity Rover, and also operates NASA's Deep Space Network of satellites.
The new study is actually an update of the researchers' ongoing work. In January, the same team published a survey investigating the bacterial genetics of samples taken from ISS surfaces in 2015. In these samples, more than 100 bacterial genes known to help make bacteria resistant to antibiotics were found. And strains belonging to a particular species of bacteria, Enterobacter bugandensis, were resistant to all nine antibiotics tested against them.
In this latest study, they hoped to find out just how dangerous these strains could be for human health. So, they compared the genetics of ISS strains to three strains of E. bugandensis gathered on Earth who had sick people. ISS strains had much in common with Earth strains, including genes associated with antimicrobial resistance and virulence (the potential of a microbe to infect a person). Based on these genetic similarities, the team estimated that ISS strains were 79% likely to cause disease or be pathogenic.
Given the results, the authors wrote "these species represent important health considerations for future missions."
Enterobacter bacteria live everywhere, even in our guts. Usually, they do not cause disease. But in people with weakened immune systems, such as hospital patients, they can become the source of serious and life-threatening infections. And the recently discovered E. bugandensis It is known to cause sepsis – a very drastic immune response to infection that can fatally close our organs – in newborns and the elderly.
These opportunistic infections are bad enough, but resistance to antibiotics has made them increasingly difficult to treat. And in space, where medical resources are limited and astronauts tend to have weaker immune systems, a potential infection can be catastrophic.
Fortunately, the authors say there is no evidence that these strains have caused any disease aboard the ISS. And there is still a lot of work to be done to find out the size of these problems, as well as whether the conditions of space travel are stimulating their growth or making them more dangerous. A scientist, for example, speculated that microgravity could actually cause bacteria to evolve faster than on Earth, or dampen the effects of antibiotics that kill germs. Future research will have to include experiments conducted directly in space.
"Whether or not an opportunistic pathogen is E. bugandensis causes disease and how much of a threat it is depends on a variety of factors, including environmental factors, "said senior author Kasthuri Venkateswaran, a researcher with the Planetary Protection and Biotechnology Group at the Jet Propulsion Laboratory in a statement. "Further in vivo studies are needed to discern the impact that ISS conditions, such as microgravity, other spaces and factors related to spacecraft, can have on pathogenicity and virulence."