New DNA technique could cut salmonella testing time

Posted by Nicole Eckersley on 6th May 2010

Researchers at Iowa State Technology, in collaboration with local company Advanced Analytical Technologies, are developing a new DNA testing technique which could cut testing for food-borne pathogen Salmonella from two days to two hours.

Lead researcher Byron Brehm-Stecher, assistant professor of food science and human nutrition, says the new technique could assist with recognising an outbreak and stopping tainted food from being delivered in the first place.

“The food has been shipped and you may not know where it is. It may be in a truck, on a shelf or in some consumer’s pantry, so time really is of the essence,” he said.

The technique isolates a gene specific to Salmonella strains, multiplying it into millions of fluorescently-labelled copies using a rapid PCR (polymerase chain reaction).  The copies are then ‘snipped up’ using a reagent, and separated out according to size.  The resulting profile is different according to what strain of Salmonella is present, allowing quick identification.  The entire process takes about two hours.

“Next-generation sequencing tools are available, but these are still too complex and expensive for routine use in the food industry,” Brehm-Stecher explained. “New approaches that are able to bridge the gap between the limitations of traditional PCR and next-generation sequencing could enhance food safety efforts by providing both rapid presence/absence testing and detailed genetic characterization of isolates.”

Outbreaks of Salmonella in spices and hydrolysed vegetable protein (HVP) in the United States and in mozarella in Australia have brought the pathogen into the public eye in recent weeks.