WOOSTER, Ohio -- The increasing incidence of a difficult-to-control bacterial illness is leading researchers to suspect that contaminated foods might be contributing to the problem.
Clostridium difficile, known as "C. diff," can cause a serious infection that is responsible for 14,000 American deaths annually, according to the Centers for Disease Control and Prevention. It's estimated there are about 500,000 U.S. cases of C. diff infection annually, and that about 3 to 5 percent of healthy adults are carriers of toxic C. diff bacteria but experience no symptoms.
Normally associated with the use of broad-spectrum antibiotics during a stay in the hospital or in other healthcare settings, C. diff infection is marked by frequent, watery diarrhea; abdominal pain or tenderness; and inflammation of the colon, or colitis. Toxins released by the bacterium can attack the lining of the intestines, and severe infections can lead to sepsis or intestinal perforation.
The elderly and immuno-compromised individuals are most at risk.
Although no cases as yet have been specifically linked with food, it's estimated that 20 to 27 percent of cases of C. diff infection are not associated with healthcare settings.
"It's not clear where they come from," said Jeffrey LeJeune, microbiologist with Ohio State University Extension and the Ohio Agricultural Research and Development Center, the outreach and research arms of Ohio State University's College of Food, Agricultural, and Environmental Sciences.
"We want to encourage public health officials to look at food as a possibility."
LeJeune, along with former doctoral student Alex Rodriguez-Palacios and University of Delaware food scientist Dallas Hoover, wrote on "Clostridium difficile: An Emerging Food Safety Risk" in a recent issue of Food Technology, the official publication of the Institute of Food Technologists. They were asked to submit the article after participating in a panel discussion on the topic at the 2011 IFT annual meeting. A PDF of the article is available by clicking here.
Rodriguez-Palacios, who is now a postdoctoral scholar at the Case Western Reserve University School of Medicine, has conducted numerous studies on C. diff and its presence in food products, particularly ground meat. His doctoral research under LeJeune was on the "Ecology and Epidemiology of Human Pathogen Clostridium difficile in Foods, Food Animals and Wildlife."
"C. diff is found throughout the environment, in water, rivers, soil, food, everywhere," said Rodriguez-Palacios. "People can pick it up from anywhere, but we are more exposed to food than to these other things."
LeJeune added: "It is widely spread in the environment, but we don't put everything in our mouths. We put food in our mouths all the time."
In their paper, the scientists reviewed 37 studies of C. diff presence in foods in both North America and Europe. From their analysis, they said it is clear that C. diff can be found in retail beef, veal, pork and poultry; seafood and fish; and in vegetables.
"Foods that are ready to eat or that we typically eat raw are more likely to be a problem," Rodriguez-Palacios said. "But we also know that a small number of food animals have C. diff at the time of slaughter. There are now recent indications of food contamination during processing."
C. diff grows at temperatures between 77 and 113 degrees F. However, the bacterium produces resistant spores that permit it to survive in harsh environments. The spores aren't inactivated until they reach a temperature of 163 to 185 degrees F for 15 minutes. “Even higher cooking temperatures are needed to be on the safe side,” Rodriguez-Palacios said.
"The problem is, we don't typically cook our foods to that high of a temperature," LeJeune said. The U.S. Department of Agriculture's cooking guidelines say to cook cuts or roasts of beef, pork, lamb and veal to a minimum internal temperature of 145 degrees F; ground beef, pork, lamb and veal to 160 degrees F; and all poultry to 165 degrees F.
"Not all pathogens are created equal," LeJeune said. "C. diff is tougher than other pathogens in terms of its environmental survival. That's probably why we find it all over."
The researchers hope their paper prompts health authorities to further consider the possibility that food could be a vector for cases of C. diff infection.
"This is especially important now because genome sequencing has shown that patients during C. diff outbreaks are getting sick with C. diff strains that cannot be explained by person-to-person transmission. Strains affecting people appear to be coming from outside healthcare centers," Rodriguez-Palacios said, citing a recent study published in BMJ Open, an online medical journal.
Determining whether C. diff is transmitted from food consumption will take some extra effort, LeJeune said.
"You have to look for it specifically," he said. "It doesn't show up on a culture plate with other foodborne pathogens, like Salmonella or E. coli."
In the meantime, the scientists encourage good food safety practices as a way to reduce the risk of C. diff infections and other potential cases of foodborne illness, including:
- Washing hands for at least 20 seconds with soap and warm water and rinsing thoroughly before eating and during food preparation.
- Frequently washing utensils and surfaces such as cutting boards, sinks and counters, and routinely disinfecting surfaces with a bleach-based solution.
- Cooking foods to proper temperatures. People most at risk for C. diff infections and other foodborne illness may want to cook foods to higher temperatures than the minimum recommendations, the scientists said.
More details on food safety precautions are available on Ohio State's Food Safety website at http://foodsafety.osu.edu; click "Ask Mom" for consumer-related information. The website is sponsored by OARDC and OSU Extension.
Update (Feb. 28, 2013): Authors LeJeune and Rodriguez have published another article on C. diff in the journal Animal Health Research Reviews, published online on Feb. 26, 2013. "Clostridium difficile in foods and animals: history and measures to reduce exposure" reviews the history of the topic and highlights for the first time areas that deserve research and administrative attention to modernize food safety actions to include this serious pathogen. A PDF of the paper can be downloaded by clicking here.