New Technique Developed For Quick Detection Of Salmonella
Source of Article: http://www.sciencedaily.com/releases/2009/02/090202121040.htm ScienceDaily (Feb. 2, 2009) — In the hours following an outbreak of
salmonella, there are many questions. And answers can be hard to find. Where
did the problem start? Can it be contained? Is the sickness likely to spread? The process, developed by Byron Brehm-Stecher,
assistant professor in food science and human nutrition, and his graduate
student Bledar Bisha,
begins with testing the food, in most cases produce, with a strip of adhesive
tape. The tape is applied to the produce, then carefully removed, taking a
sample of whatever is on the skin of the produce. That sample is then put on
a slide and soaked in a special warm, soapy mixture that contains a genetic
marker that binds with salmonella and gives off a fluorescent glow when
viewed under an ultraviolet light. Use of this genetic marker approach is
called Fluorescent In-Situ Hybridization, or FISH. The approach can tell investigators if the produce is contaminated with
salmonella in about two hours. "This method is rapid, it's easy, and it's cheap," said Brehm-Stecher. Current methods of detecting salmonella take one to seven days. Brehm-Stecher and Bisha
call the process "tape-FISH" and note that it could be an important
technique for salmonella investigators. "I think this will be good tool in outbreak investigation and routine
surveillance especially since all you need is tape, a heat block, a small
centrifuge and a fluorescence microscope," said Brehm-Stecher.
"It has the potential to be very portable." Brehm-Stecher's and Bisha's
findings will be published in the journal Applied and Environmental
Microbiology, published by the American Society of Microbiology. Once at a location where an outbreak of salmonella has occurred,
investigators can test the produce for contamination. Outbreaks can be due to
other factors such as food preparation. Once investigators find the origin of the salmonella, they can take steps
to contain it, said Brehm-Stecher. Salmonella can be found on produce such as tomatoes, cilantro, peppers,
spinach and others. The produce can be contaminated while it is in the fields
or during processing. Washing the produce thoroughly can help, but cannot
ensure the produce will be safe. The tape-FISH technique can also be used to test produce that is not
suspected of being contaminated, but the volume of produce that would need to
be tested may make this impractical. However, the technique could be very
valuable as a basic research tool. Researchers could investigate how
salmonella and other types of organisms interact on produce surfaces, said Brehm-Stecher. This is the first application of tape-FISH to salmonella, but the idea came
to the ISU researcher while reading about art restoration. In 2008, Brehm-Stecher read about an Italian
group that was using a similar approach to look for bacteria on ancient
catacombs. Those researchers were hoping to identify and remove bacteria that
were slowly eating away at the relics. After some classroom discussion with his students, Brehm-Stecher
decided that using the FISH on produce could be useful and began researching
the idea with Bisha. Together, they were able to
apply the method to produce and made several improvements in speed and
sensitivity over the existing tape-FISH approach. Brehm-Stecher
hopes that his tape-FISH approach can help speed investigations of produce
contamination, such as last summer's outbreak of Salmonella Saintpaul, which was eventually traced to imported
jalapeno and Serrano peppers. Adapted from materials provided by Iowa State
University. |
Copyright (C) All rights reserved under FoodHACCP.com
If you have any comments, please send your
email to info@foodhaccp.com
