Orbiting 250 miles above the Earth, the International Space Station (ISS) is home to a handful of scientists and astronauts constantly inhabiting the orbital outpost — and to a host of microbes that have taken up residence on board the research facility. Among these microbes, scientists have recently discovered five strains of Enterobacter — a drug-resistant hospital bug known to cause a series of dangerous infections, reports RT.
The fact that germs can be found on the ISS is hardly a revelation — “Where there are people, there are bacteria, even in space,” NASA stated a few years ago, when the agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California, published a study on the microbes found in dust particles collected from the space station’s air filters.
Nevertheless, finding five different varieties of Enterobacter onboard the orbiting laboratory could pose a threat to future space station expeditions, especially given the drug-resistant profile of the bacterium strains.
According to Phys.org, the five strains of Enterobacter were isolated from the ISS in March 2015 and were uncovered inside the facility’s space toilet and on the exercise platform that the astronauts use to keep in shape and combat the muscle atrophy associated with living in a microgravity environment.
Upon discovering these bacteria, the JPL launched an investigation into the genetic make-up of each individual strain and found them all to be genetically similar to three Enterobacter strains newly identified on Earth. Known as Enterobacter bugandensis, these three bacteria strains “had been found to cause disease in neonates and a compromised patient, who were admitted to three different hospitals” — two in the U.S. and one in East Africa, JPL microbiologist Dr. Kasthuri Venkateswaran said in a statement.
Writing in the journal BMC Microbiology, Venkateswaran and his colleagues underlined that the newfound ISS microbes are not harmful to the space station’s crew in their current form. Nevertheless, computer simulations conducted by the JPL team showed that the Enterobacter bugandensis discovered in space has a 79 percent probability of becoming pathogenic — meaning that it could end up infecting astronauts and causing disease.
“Given the multi-drug resistance results for these ISS E. bugandensis genomes and the increased chance of pathogenicity we have identified, these species potentially pose important health considerations for future missions,” said study lead author Dr. Nitin Singh, a researcher at JPL’s Biotechnology and Planetary Protection Group.
“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.”
In order to determine the genetic profile of the space bugs, the scientists compared the five Enterobacter bugandensis strains to the genomes of nearly 1,300 Enterobacter strains collected on Earth. The analysis revealed that the ISS bacteria were resistant to five of the most commonly used antibiotics, including penicillin and oxacillin. In addition, the microbes turned out to be resistant, intermediate resistant, or susceptible to four other antibiotics.
While the new study shows that the hospital bug found on the ISS could cause problems for future astronaut missions, the team emphasized that more research is needed before anyone can establish how infectious Enterobacter bugandensis could be in space.
“Whether or not an opportunistic pathogen like E. bugandensis causes disease and how much of a threat it is, depends on a variety of factors, including environmental ones,” Venkateswaran pointed out.
The unique conditions on board the ISS — which include microgravity, space radiation, and elevated carbon dioxide levels — have been known to increase microbes’ resistance to antibiotics, notes RT. This means that the Enterobacter bugandensis found in space could end up becoming more virulent over time.
According to AntiMicrobe.org, Enterobacter bacteria can cause a wide array of infections that could affect the lungs, the lower respiratory tract, and the urinary tract. These microbes are also known to produce ophthalmic, skin, and soft-tissue infections, as well as intra-abdominal infections. One particular strain of Enterobacter, called E. sakazakii, has been linked to sepsis with meningitis in newborns.