What is in this article?:
- The recent outbreak of foodborne illness in Germany serves as a reminder of the power microbes hold over humanity, in spite of scientific, medical, and technological advances.
- University of Arizona research teams are working toward improving food safety and developing new and effective weapons against an emerging breed of microbes that's becoming increasingly resistant to conventional antibiotics.
Copper vs. stainless steel
Rensing pointed out that the microbes' growing resistance to antibiotics calls for alternative and equally effective means of fighting them.
Research in Rensing's lab involves innovative ways to prevent harmful microbes growing on surfaces. Recent trials showed that using copper alloy instead of stainless steel on touch surfaces in hospitals reduced the number of bacteria by 66 percent to 99 percent.
"Traditionally, hospitals have been using stainless steel because of its clean and sterile appearance," Rensing said. "Copper, on the other hand, is far superior in terms of hygiene. It may begin to look a bit crummy over time, but we discovered it kills bacteria in less than a minute. On stainless steel, those same bacteria are still alive after 24 hours or more."
In collaboration between Ravishankar's and Rensing's lab, the researchers are evaluating how copper could help make foods safer. For example, Salmonella was inactivated within 10 minutes to 15 minutes on copper alloy surfaces.
"Jorge Fonseca, our collaborator at the UA Yuma Agricultural Center, has looked at cross-contamination of lettuce with coring tool or harvesting knife," Ravishankar said. "If a harvester uses a contaminated tool, how many lettuce heads can it contaminate?"
To find out, Fonseca's team cut 75 lettuce heads and analyzed them for bacterial contamination in the lab. Several lettuce heads, including number 75, the one cut last, were contaminated.
"What this means is that if you have one fecal spot in a field, for example from an animal dropping or contaminated irrigation water, that is enough to contaminate many rows of lettuce."
This research shows that simple measures, such as replacing steel blades in harvesting knives and lettuce coring tools with copper would greatly lower the risk of contamination in produce.
Contaminated irrigation water poses a significant risk, especially in agricultural areas that rely heavy on it. Gerba and his research group have studied irrigation waters in Arizona and Mexico for a decade.
"About 70 percent of produce in the U.S. is irrigated," Gerba said, "but surprisingly little is known about the contamination of irrigation systems and the microbial quality of irrigation waters."
Surveying EHEC in Arizona
In addition to developing new ways of preventing microbes from contaminating food and sensitive areas such as hospital settings, other research at the UA takes a closer look at the complex interactions between bacterial pathogens and their hosts.
Research in Viswanathan's lab centers on pathogenic E. coli as a group. His team is starting a project to study EHEC in the Tucson area and from outbreaks in Arizona.
One recent finding came unexpected and offers a glimpse into the complex evolutionary relationships between host and microbe. Viswanathan's team discovered that one strain of E. coli secretes a protein that is toxic to gut cells, but the bacteria also produces a second protein that counteracts the toxic effect of the first.
"This is an interesting process where the bacteria actually protect their host cells from damage," Wilbur said. "From an evolutionary perspective, it makes sense for the microbes to not kill the very cells they're living on."
Taken together, "all those efforts just help reduce the burden of contamination and minimize exposure to germs," Rensing said. "Microbes are everywhere on this planet, and they change constantly. This means we will never find a silver bullet, something that will prevent outbreaks once and for all."