Earlier this year, an outbreak of salmonella in the US caused by infected eggs resulted in thousands of illnesses before a costly recall could be implemented. But University of Missouri researchers say their faster and more accurate test could have prevented the contaminated eggs from being shipped to stores.
“The new test will keep companies from shipping contaminated products and thus keep salmonella-infected products out of consumers’ hands,” says associate food science professor Azlin Mustapha.Salmonella testing in poultry is important because it persists in birds’ spleens and reproductive tracts, and an infected bird passes the infection on to all of its eggs.
The most commonly used test can take up to five days to produce results. By contrast, Prof Mustapha’s test uses a process known as polymerase chain reaction (PCR), and cuts testing time to as little as five to 12 hours.
PCR-based testing methods for salmonella have been available for use by the food industry for years, but until now have often produced false-positive results, because they don’t differentiate between live and dead salmonella – and only live salmonella cells trigger salmonellosis.Prof Mustapha modified the PCR test by adding a dye to the test sample. The dye is absorbed by dead salmonella cells, enabling the PCR test to ignore them. The reduced testing time will enable companies to have accurate test results before a product is shipped. With current tests, food could be in stores before the test results are available.