The problem with Listeria monocytogenes is how much of it gets into people's digestive systems, reports the Food Safety Consortium in its latest newsletter.

Michael Johnson (left), University of Arkansas professor of food science, presents a planner to Martin Wiedmann of the Cornell University food science faculty following his presentation.

"Everyone gets exposed, but few people get sick," explained Martin Wiedmann of Cornell University during a seminar in October at the University of Arkansas.

L. monocytogenes is widespread and each person is likely to ingest between one million and one billion of this bacterium a year. Those who ingest too much are the ones who become ill, Dr Wiedmann said. The majority of listeriosis outbreaks come from contaminated deli meats.

Dr Wiedemann is an associate professor of food science at Cornell where he also serves as his department's graduate studies director. He spoke to a University of Arkansas food science seminar on molecular studies of the transmission of L. monocytogenes.

"Our overall goal is to generate an improved understanding of the transmission of foodborne bacterial pathogens from farm animals and from foods to humans," Dr Wiedmann said of his Cornell laboratory's work. "A better understanding of the transmission pathways of foodborne pathogens is necessary to design better strategies to prevent and control human disease. Both basic and applied research work in our lab is thus targeted towards developing the scientific knowledge necessary to improve our ability to prevent foodborne diseases."

Specifically, Dr Wiedmann's research seeks to understand the differences among the abilities of strains of L. monocytogenes to cause disease in humans and animals. His team's work also explores the role of stress response systems in the pathogen's ability to survive in foods and cause disease.

Other objectives in Dr Wiedmann's lab include better understanding of the evolution of the virulence of L. monocytogenes virulence and of Salmonella's ecology transmission.

Dr Wiedmann noted his research team collaborates frequently with other institutions and agencies. One example was a project with the New York State Department of Health on molecular fingerprinting of L. monocytogenes.

"Our research group recently contributed to the detection of a large multi-state outbreak of human listeriosis cases which was ultimately linked to consumption of contaminated hot dogs and deli meats," Dr Wiedmann said.