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Spring/Summer 2012

Food scientist’s research helps make animal food products safer

By Kim Markesich

According to the Centers for Disease Control, foodborne diseases cause up to 81 million illnesses and as many as 9,000 deaths each year in the United States. It is difficult to pinpoint the actual number of illnesses, as most cases of food poisoning go unreported.

Kumar Venkitanarayanan, professor in the Department of Animal Science, has been involved in multiple research projects focusing on food safety, specifically, using food-grade plant compounds to reduce bacterial threats.

Salmonella enteritidis is a major foodborne pathogen, causing more than a million cases of food poisoning each year in the U.S., with chicken and eggs serving as the most common vehicles of infection. The disease is spread when Salmonella bacteria colonize within the chicken intestine and ovaries and subsequently contaminate the eggs and meat.

Venkitanarayanan is working on two USDA-funded projects focusing on Salmonella infection, one concentrating on broiler chickens and the other on layer chickens. Two plant compounds, trans-cinnamaldehyde, a product derived from cinnamon, and caprylic acid, a natural fatty acid found in coconut oil and goat’s milk, have shown efficacy against Salmonella. These plant molecules interact by blocking expression of specific genes necessary for Salmonella colonization within the chicken gastrointestinal tract. When chicken feed is supplemented with these plant extracts, there is a reduction of Salmonella in the chicken intestine, which in turn reduces the contamination in meat and eggs. These plant ingredients are also effective when used in an eggshell wash.

Venkitanarayanan's research has also addressed mastitis, a major economic concern for the dairy industry, costing approximately two billion dollars annually. Traditionally, mastitis is treated with intramammary infusions of antibiotics. However, with the emergence of drug-resistant pathogens, antibiotic cure rates are decreasing. And, consumers do not want antibiotic residues in their food. In a project supported by USDA’s National Institute of Food and Agriculture (NIFA), Venkitanarayanan is investigating the potential of caprylic acid and trans-cinnamaldehyde for treating and controlling mastitis in cows. Laboratory results have shown that these plant molecules are effective against mastitis, and continued research may lead to new antimicrobial tools for controlling the disease.

Clostridium difficile is a major cause of intestinal disease in humans and is usually found in hospital patients undergoing long-term antibiotic therapy, which reduces natural gut microflora. With fewer good bacteria in the gut, the Clostridium bacteria overtake the intestines, causing inflammation and tissue death. There have been several recent studies that suggest the possibility of Clostridium’s presence in our food supply. Venkitanarayanan is involved in a USDA-supported multi-state project to examine ground beef, pork and chicken for sale in retail stores evidence of Clostridium contamination. Because this pathogen produces spores that are heat resistant, the study will also consider new time and temperature cooking conditions for ground beef.

In addition to his current projects, Venkitanarayanan has also been involved in research on Cronobacter sakazakii, a pathogen involved in several outbreaks of neonatal illness tied to infant formula. The Cronobacter bacteria form a thick biofilm resistant to disinfectants, making it difficult to eradicate. The plant extract trans-cinnamaldehyde was found to disrupt the genes necessary for biofilm formation, thus making the bacteria more sensitive to disinfectants, opening the door for a potential commercial application in disinfecting compounds.

Says Venkitanarayanan, “Many bacteria are gaining resistance to antibiotics. There are a number of genes in the bacteria that are involved in making them resistant to antibiotics. We are finding that some of the plant molecules make the bacteria sensitive to antibiotics by turning down or switching off those antibiotic-resistant genes, making the antibiotics more effective against these resistant bacteria.”

“There are a lot of things that we have yet to tap from the natural sources,” he continues. “Plants have existed longer than humans on the planet, and plants produce about 5,000 molecules, most of them to protect against insects and infection.”

While he is very focused on researching foodborne pathogens, Venkitanarayanan also points out that we all are responsible for preparing our food properly. He says, “It’s not easy to produce bacteria-free foods. There are a lot of sources of bacterria — from the environment, from the animal’s intestine, from the human hands touching the food, and water we use to wash the products, so people need to be careful consumers. They have to cook food properly and prepare it properly to avoid cross contamination. Use safety measures at home. You cannot fully rely on the industry to produce bacteria-free food. It is not possible.”