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Fish speeds Salmonella detection.

Salmonella can cause serious and sometimes fatal infections in young children, the frail or the elderly, as well as those who have weak immune systems. Healthy persons infected with the bacteria can experience fever, diarrhea, nausea, vomiting and abdominal pain.

Iowa State University researchers have developed a technique for testing for the presence of Salmonella that may yield fast results. First, a strip of adhesive tape is applied to a product, such as produce, and then is carefully removed, taking a sample of whatever was on the skin.

That sample is then put on a slide and soaked in a warm, soapy mixture that contains a genetic marker that binds with Salmonella and gives off a fluorescent glow when viewed under an ultraviolet light. This technique, fluorescent in-situ hybridization (FISH), shows researchers if the produce is contaminated with Salmonella in about two hours. Current methods of detecting Salmonella take up to one week.

The researchers indicate that FISH will be a good tool for outbreak investigations and routine surveillance, especially since all that is needed is tape, a heat block, a small centrifuge and a fluorescence microscope. The technique can test large volumes of produce, and could be valuable as a basic research tool. Researchers could see how Salmonella and other types of organisms interact on produce surfaces.

The FISH concept came to ISU researchers after they learned about others that were using a similar approach to look for bacteria in ancient catacombs. Those researchers were hoping to identify and remove bacteria that were slowly eating away at the relics.

Investigators made several improvements in speed and sensitivity over the existing tape-FISH approach. They hope that the tape-FISH approach can help speed investigations of produce contamination, such as a 2008 outbreak of Salmonella St. Paul, which was eventually traced to imported jalapeno and Serrano peppers. S. St. Paul is the sixth most common serovar infecting humans in the United States. It has emerged in other countries, such as Japan.

Further information. Byron Brehm-Stecher, Department of Food Science and Human Nutrition, Iowa State University, 2312 Food Sciences Building, Ames, IA 50011; phone: 515-294-6469; fax: 515-294-8181; email:

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Publication:Emerging Food R&D Report
Date:Nov 1, 2016
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