Listeria 'tricks' cells to infect humans

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WEST LAFAYETTE, Ind., Oct. 25 (UPI) -- Listeria bacteria, a source of food-borne illness, tricks cells in the body's intestines to pass through those cells and make people sick, researchers say.

Researchers at Purdue University found that listeria, even in low doses, somehow triggers intestinal cells to express a protein that acts as a receptor for listeria, a university release said.

This may allow the bacteria to enter the cells in the intestinal wall and exit into a person's bloodstream, the researchers say.

"It's possible that host cells generate more of these proteins in order to protect themselves during a stressful event such as infection," said Kristin Burkholder, a former Purdue graduate student now a postdoctoral researcher at the University of Michigan Medical School. "Our data suggest that listeria may benefit from this by actually using those proteins as receptors to enhance infection."

Listeria monocytogenes bacteria can cause fever, muscle aches, nausea and diarrhea, as well as headaches, stiff neck, confusion, loss of balance and convulsions, if it spreads to the nervous system.

The U.S. Centers for Disease Control and Prevention says it sickens about 2,500 and kills 500 people each year in the United States.

The findings suggest that listeria may pass between intestinal cells to sort of seep out of the intestines and into the bloodstream to cause infection.

"The infective dose is very low. Even 100 to 1,000 listeria cells can cause infection," Arun Bhunia, Purdue professor of food science, said. "We believe that these mechanisms are what allow listeria to cause infections at such low levels."