November 2010

How Salmonella Bacteria Spread

Some Salmonella bacteria are fast-replicating, quick-moving and armed with a needle-like complex that can penetrate cells in the human gut. The new findings may help explain how Salmonella can spread so efficiently.

Salmonella are the most frequently reported cause of food poisoning in the United States. Researchers at NIH’s National Institute of Allergy and Infectious Diseases (NIAID) decided to take took a closer look at how the bacteria might spread from cell to cell or from person to person.

Using high-powered microscopes, the scientists found that a subset of Salmonella have long whip-like “tails” that let them move freely within infected cells. These bacteria multiply more quickly than other Salmonella. They also have a “needle complex” that helps them pierce cells and inject their proteins. The bacteria seem especially well-suited for invading other cells.

Cells containing these Salmonella were quickly pushed out of a simple layer of lab-grown cells, which led to the release of bacteria. A similar process occurred in certain tissues of infected mice. The shedding cells set off an inflammation cascade. These findings may help explain the inflammation seen in Salmonella infections.

“Unfortunately, far too many people have experienced the debilitating effects of Salmonella, which causes disease via largely unexplained processes,” says NIAID Director Dr. Anthony S. Fauci. “This elegant study provides new insight into the origins of that inflammatory disease process.”