Researchers have found that a strain of bacteria found in hospitals on Earth and associated with disease is also present on the International Space Station (ISS).

The research from NASA’s Jet Propulsion Laboratory (JPL) in California showed that five strains of the bacterium Enterobacter were found in samples taken from a toilet on the station and some of its exercise equipment in March 2015.

Comparing the samples on the ISS to 1,291 genomes of Enterobacter on Earth, the team were able to narrow down which species were present, and these had been known to cause health problems on our planet. The findings were published in BMC Microbiology.

“We revealed that genomes of the five ISS Enterobacter strains were genetically most similar to three strains newly found on Earth,” Dr Kasthuri Venkateswaran from JPL, the corresponding author on the study, said in a statement.

“These three strains belonged to one species of the bacteria, called Enterobacter bugandensis, which had been found to cause disease in neonates and a compromised patient, who were admitted to three different hospitals (in east Africa, Washington state and Colorado)."

By comparing the strains on the ISS to those on Earth, the researchers also wanted to find out if those on the station showed signs of antimicrobial resistance. And they found that they did show some multi-drug resistance, which could cause some issues.

“[T]hese species potentially pose important health considerations for future missions,” Dr Nitin Singh, the study’s lead author, said in the statement. “However, it is important to understand that the strains found on the ISS were not virulent, which means they are not an active threat to human health, but something to be monitored."

While not immediately dangerous to the humans on board, the researchers did note there was a 79 percent probability that they could cause disease. But they noted further studies were needed to see what impact the conditions on the ISS, including being in microgravity, had on the bacteria.

This isn’t the first time we’ve heard about bacteria on the ISS. Last year, astronauts claimed to have found bacteria living outside the station – although that was later shown to have been likely carried up by a spacecraft. And researchers have been using tools on board the station to identify microbes in space.

But the issue of disease is an important one for future missions. If humans are going to travel far beyond Earth, with no chance of visiting a doctor back home, we’ll need to make sure they have few chances of catching some sort of disease that could put the mission in jeopardy. Working out what bacteria can grow on the station is a key part of that.