Bacteria contaminating ISS water dispenser not more dangerous than earthbound strains: Study

Two particularly tenacious species of bacteria have colonised the potable water dispenser aboard the International Space Station (ISS), according to a new study which suggests that they are no more dangerous than closely related strains on the Earth.

According to the researchers, including Aubrie O'Rourke from the Craig Venter Institute in the US, periodic sampling showed that two bacteria, Burkholderia cepacia and later on, Burkholderia contaminans, were contaminating the drinking water at the ISS.

The study, published in the journal PLOS, said these microbes belong to a group of related Burkholderia species that cause opportunistic lung infections in people with underlying health conditions.

It added that these are very difficult to kill using common sterilisation techniques, and have persisted in the water dispenser despite periodic flushing with an extra-strength iodine cleaning solution.

In the study, the scientists sequenced the genomes of 24 strains of the bacteria collected from 2010 to 2014.

All of the B. cepacia and B. contaminans strains were highly similar, and likely descended from original populations of these two bacteria that were present in the water dispenser when it left Earth, the researchers said.

The study concluded that the two bacterial species living within the dispenser are no more dangerous than similar strains that might be encountered on Earth.

It said in the event of an infection, the bacteria can still be treated with common antibiotics.

"Within each species, the 19 B. cepacia and 5 B. contaminans recovered from the ISS were highly similar on a whole genome scale, suggesting each population may have stemmed from two distinct founding strains," the researchers wrote in the study.

According to the study, the differences that can be observed among the isolates of the same species are primarily located within their plasmids -- circular DNA found in the cells of bacteria.

"We find that the populations of Burkholderia present in the ISS PWS are likely are not more virulent than those that might be encountered on planet, as they maintain a baseline ability to lyse macrophage (immune system cells), but remain susceptible to clinically used antibiotics," they added.