Studying guinea pigs and genetically modified mice, scientists at the Pasteur Institute in Paris demonstrated that the bacterium, known as Listeria monocytogenes, has a protein that is much like a key. The protein opens a lock and interacts with a receptor in the intestine to enter the bloodstream. Doctors can already treat the infection, called listeriosis, with standard antibiotics. But there is concern that the bacterium will develop resistance to antibiotics. The study appears in the journal Science.
Listeria is commonly present in soil, vegetation and sewage.
It can contaminate raw vegetables and processed foods requiring refrigeration, such as soft cheeses, pate and meat spreads, processed meats such as hot dogs, and smoked fish. About 500 deaths a year are reported in the United States. Infection of a pregnant woman early in pregnancy generally causes a miscarriage. In otherwise healthy adults, symptoms typically range from gastrointestinal illness to mild fever and headache. To cause foodborne infection, Listeria must move through the stomach and then cross the intestine to enter the bloodstream, where it disseminates to the central nervous system and the placenta.