Food poisoning bug lurks in body

WASHINGTON - Listeria, a common food poisoning bug, may be able to lurk in the body and perhaps even spread without causing symptoms, say United States researchers.

The bug may re-emerge from hiding weeks or months after infection to make a victim sick again or to spread to someone else, they report in the journal Science.

The finding by researchers at Stanford University School of Medicine suggests that an unwitting food worker could transmit the bacteria - in a way reminiscent of Typhoid Mary, an Irish-born cook who caused several outbreaks of typhoid in the United States nearly 100 years ago.

The researchers infected young mice with Listeria monocytogenes bacteria and used a special imaging method to see where the bacteria went.

By 18 hours after infection, the mice seemed to have largely rid themselves of the bacteria.

"After three to nine days, depending on the dose, the signals reappeared in different locations in many of these animals and persisted for two or three days before waning again," the researchers wrote.

The mice did not get ill with the second appearance.

When the mice were killed and dissected, the bacteria were found in the gallbladders - where the Salmonella typhosa bacteria that cause typhoid are also known to hide.

That suggested the same thing might go on in people, said Jonathan Hardy of Stanford.

Listeriosis can make some people very sick and can kill those with weakened immune systems. It kills about 500 people a year in the US and can cause miscarriages.

"Twenty to 40 per cent of people with listeriosis die even after antibiotic treatment," Mr Hardy said.

- REUTERS