Grapes, Melons Implicated in Outbreaks

According to researchers , there is a new study on seedless green grapes which caused a salmonella outbreak that sickened 30 people across six Western states last summer and fall. Researchers were surprised to find that the outbreak of Salmonella serotype senftenberg most often found in meats and poultry was outwardly spread to people through grapes.

Dr.Alicia, at the International Conference on Emerging Infectious Diseases, told that the outbreak of S. senftenberg caused primarily diarrhea and abdominal cramps. Symptoms ranged from mild to severe. "Two teenage girls were sick for several weeks," she said. The investigators were unable to track the cause of the outbreak to its origin, but sophisticated DNA fingerprinting tests showed the strain of S. senftenberg was the same among samples taken from people infected in California, Colorado and New Mexico.

Cronquist suggested the bacteria may have infected the fruit during harvesting or in storage before it was distributed. In another case reported at the meeting, epidemiologists in California determined precut melons -- cantaloupes, watermelon and honeydew -- were the likely cause of another Salmonella outbreak, this one caused by the S. poona serotype.

Kris Carter, a fellow with the California Epidemiologic Investigation Service, interviewed 23 patients who came down with the S. poona infections in June and July of 2001 and was able to determine an association with eating melons. However, we didn't find any real association until we asked the people if they had eaten precut melons," she said. For example, more than half the people who became ill recalled eating precut cantaloupes. About 40 percent of the people who were ill remembered eating precut honeydew. In fact, she said, all the people who developed symptoms who remembered eating honeydew said they ate precut honeydew.

Carter said it is possible the bacteria on the surface of the melons somehow infected the fruits when it was cut. It also is possible that because precut melon sits around a while before being eaten, the bacteria has an opportunity to grow, she said. She said people who want to avoid infection from fruits should wash them first and eat them soon after preparation.

"We are seeing more of these types of outbreaks in the past couple of years," said Jenny Lay, an epidemiologist with the Foodborne and Diarrheal Disease Branch of the CDC's National Center for Infectious Diseases. She concurred basic food safety steps -- such as washing food -- could reduce the risk of infections.

Other researchers looked at the process of heating lettuce to increase its shelf life. By dipping iceberg lettuce into warm water baths, the vegetable resists brown discoloration. However, Larry Beuchat, research professor of food safety at the University of Georgia, Athens, found the treatment also apparently facilitates growth of Listeria monocytogenes, an organism that can cause severe infections, during storage at refrigeration temperature.

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