Alcohol increases bacterium's virulence.

New research suggests that ethanol, the intoxicating ingredient in alcoholic beverages, may step up the virulence of a particular bacterial species.

The baeteriumAcinetobacter baumannii is responsible for numerous infections, such as pneumonia, meningitis, and urinary tract infections in people. Recently, this bacterial species has been implicated in blood infections in more than 100 U.S. soldiers stationed in Iraq.

Michael Smith and Michael Snyder of Yale University had been using A. baumannii in their studies of interactions between bacteria and yeast. The researchers noticed that colonies of the bacterium grew better when they were near yeast than when they weren't. They traced the effect to the ethanol that the yeast was secreting while fermenting sugar.

To see what effect ethanol has on A. baumannii living inside other organisms, Smith and Snyder fed the bacteria to nematode worms. The scientists then dosed the worms with small amounts of ethanol.

They found that worms infected with the bacteria laid significantly fewer eggs and had life spans only about 80 percent as long as did worms infected with a mutant version of the bacterium that didn't respond to ethanol.

Although the researchers aren't sure how ethanol increases A. baumannii's virulence, they suggest that their research could displace a common misconception among drinkers. While some people believe that drinking alcohol can kill off a budding infection, Smith notes that drinking may actually make some bacteria more powerful and speed along a nascent infection.--C.B.