September 17, 2008 / 10:14 PM / 9 years ago

Study explains how Listeria attacks mother, fetus

CHICAGO (Reuters) - French researchers have discovered how food-borne bacteria can make the jump from a pregnant mother to her unborn child, a finding that may lead to new ways of protecting a fetus from potentially deadly infections.

Researchers at the Institut Pasteur in Paris studied Listeria monocytogenes, a pathogen that infects 2,500 people a year in the United States, killing 500 each year.

Pregnant women are about 20 times more likely than other healthy adults to get listeriosis, an infection that can often result in miscarriage and stillbirth.

About one-third of listeriosis cases happen during pregnancy, according to the U.S. Centers for Disease Control and Prevention.

People get listeriosis from eating contaminated food. Listeria can cross from the intestine into the blood stream. But how it crosses the placental barrier and into the fetus has been unclear.

A team led by Marc Lecuit studied listeria in both gerbils and mice and found two bacterial invasion proteins, InlA and InlB, are needed for listeria to cross the placental barrier and infect the fetus, the team reported in the journal Nature on Wednesday.

Lecuit and colleagues think by blocking one or both of these pathways, it may be possible to keep a mother from passing the infection to her fetus.

In addition to pregnant women, listeriosis affects older people, newborns and adults with weakened immune systems.

Symptoms include fever, muscle aches, and sometimes nausea or diarrhea. If infection spreads to the nervous system, it can cause headache, confusion, loss of balance or convulsions.

Editing by Maggie Fox and Cynthia Osterman

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