Research on the International Space Station (ISS) has discovered ways to lessen virulence of a common food poisoning disease organism, NASA announced.

The organism that can cause food poisoning in humans, the salmonella bacteria, causes an estimated 40,000 cases of food poisoning annually in the United States alone.

Salmonella and other organisms can grow rapidly in food that isn’t kept either hot (over 180 degrees Fahrenheit) or cold (less than 40 degrees). Poor washing of plates, silverware, pots and other items also can contribute to the problem.

Such food poisoning outbreaks can cause severe illness in some persons (especially the elderly, infants and people with compromised immune systems), and outbreaks among military personnel can severely degrade mission readiness.

Research on the ISS showed how to reduce the virulence of salmonella organisms, with experiments discovering key elements of the bacteria’s disease-causing potential that hold promise for improving ways to fight food-borne infections on Earth.

"This research opens up new areas for investigations that may improve food treatment, develop new therapies and vaccines to combat food poisoning in humans here on Earth, and protect astronauts on orbit from infectious disease," said Julie Robinson, program scientist for the ISS at Johnson Space Center in Houston.

The salmonella experiments were flown on space shuttle missions to the ISS in September 2006 and March 2008. The 2006 experiment results allowed researchers to identify a molecular "switch" that appears to control salmonella’s response to spaceflight in unique ways not observed using traditional experimental approaches on Earth. The 2006 results showed that the space environment causes a short-term alteration in salmonella virulence: the bacteria cultured in space were more virulent than those on Earth.

The 2008 experiment confirmed the 2006 results and demonstrated that a change in the growth environment of the bacteria controls its virulence. There is no evidence that the space-grown bacteria sustained these effects for long periods after returning to Earth.

In addition to finding a leading candidate as to why the bacteria becomes more virulent in space, results from the 2008 experiment helped researchers identify ways to counter the virulence effect.

A research team led by Cheryl Nickerson of the Biodesign Institute at Arizona State University in Tempe found that adjusting the ion content of the bacteria’s environment can turn off the rise in virulence caused by spaceflight.

The space experiments helped researchers show that a mechanical force known as "fluid shear," the motion of fluid that cells sense as fluid passes over their surface, could have a dramatic effect on salmonella’s disease-causing potential.

Lower fluid shear conditions, it turns out, are found both in microgravity and in human intestines. The bacteria cultured in space are more virulent, and Nickerson’s work showed that by modifying the medium in which the cells are grown, the virulence could be reduced, or turned off.

In other words, space travel may trick the bacteria into behaving as though they were in the low fluid shear environment of the intestine, essentially turning on a switch inside the microbe that increases virulence. Changing the chemistry of the medium in which the bacteria are cultured reverses this effect.

"To our knowledge, no one had previously looked at a mechanical force like fluid shear on the disease-causing properties of a microorganism during the infection process," Nickerson said. "We can use the innovative research platform of the space station to contribute to new translational advances for the development of new strategies to globally advance human health."

Experiments were managed by Ames Research Center at Moffett Field, Calif., supporting the Exploration Systems Mission Directorate. The Nickerson team’s initial findings were published in the Proceedings of the National Academy of Sciences, and their most recent findings published in the journal PLoS ONE.

For more about the salmonella research conducted in space, visit: http://www.nasa.gov/mission_pages/station/science/experiments/MDRV.html