Colorado State University’s Study of Listeria Garners $2 Million Grant

A Colorado State University animal sciences professor and a team of collaborators have received $2 million to study and find ways to control a bacterium that kills hundreds in the United States each year and causes meningitis in people with a weakened immune system as well as miscarriages and stillbirths in infected pregnant women.

John Sofos and his team will investigate Listeria monocytogenes, a bacterium responsible for an estimated 2,500 cases of food-borne illness each year, including 500 deaths, from contaminated ready-to-eat meat and poultry products and other foods. The bacterium most commonly contaminates food at facilities that produce ready-to-eat packaged food, retail facilities and in the home when food products are not handled within proper food safety guidelines. The bacterium is found most often in products such as processed meats like hot dogs, deli meats and salads, smoked seafood, raw milk and soft cheeses.

"Food-borne illness from Listeria has the most significant impact on pregnant women, newborns, the elderly and adults with weakened immune systems," said Sofos said. "It can be best prevented through a number of food-safety protocols along links in the food system."

The incidence of Listeria infections is much higher in pregnant women than other adults. In fact, nearly a third of all Listeria cases are pregnant women, while the death rate of those infected is 20 to 30 percent. Once in the bloodstream, Listeria travels throughout the body but tends to gravitate toward the central nervous system and the placenta, making fetuses unusually prone to Listeria infections, which can cause miscarriages, stillbirths or serious health consequences for the fetus after birth.

In the last several years, large-scale outbreaks have led to initiatives, including a new regulation for, within regulatory agencies and the food industry, to control the presence of the bacterium, and prevent its survival and growth in ready-to-eat products.

Listeria is a bacterium that commonly exists in nature. It is found in soil, groundwater, plants and animals, and is often carried by humans and animals. Because the bacteria can survive and grow under refrigeration, it can be particularly difficult to control in ready-to-eat food products that are not cooked immediately before they are consumed.

Sofos and his collaborators will study how to control the transmission of Listeria in facilities where food is processed as well as at the food-service; retail and consumer level, and will communicate the most effective risk reduction and control strategies to those facilities including meat and poultry processors, and food service and retail locations.  The team will also develop models that can be used to predict transmission of the bacteria along different links of the food supply system to propose more effective intervention strategies and to reduce the risk of contamination.

The project represents a multidisciplinary, collaborative effort among scientists from several institutions and states, and includes applied research, outreach and education components. Project director Sofos is joined in this effort by co-investigators Martin Wiedmann of Cornell University and Harshavardhan Thippareddi of the University of Nebraska. Collaborators also include Professors Pat Kendall, a food safety expert, and John Scanga, a meat safety expert, of Colorado State University; Lydia Medeiros of Ohio State University; and Liz Boyle of Kansas State University. In addition, industry associations and various health departments at the state and national level have expressed their support for this project.

Once data are gathered about contamination patterns, the study can pinpoint sources of Listeria contamination within facilities and model the impact of those sources on food products. Training will be provided to food processors, retail and deli operators and managers, and health inspectors through seminars and online educational programs conducted by Thippareddi, Scanga, Boyle and other members of the team. In addition, educational opportunities will be developed for high risk consumers and their health care and food service providers by Kendall and Medeiros.

The symptoms of Listeria infections include gastrointestinal distress within two 2 to three3 days, followed by fever, chills, headaches, muscle aches and back aches 11 to 70 days after exposure.  

The grant, which was awarded by the National Integrated Food Safety Initiative of the U.S. Department of Agriculture, provides funding for the project to begin this month and continue through September 2009.