Food scientists have traditionally relied upon culture-based methods for food safety testing. Due to the proven reliability of these methods and their long history of use in food safety labs, inspectors have been reluctant to adopt more “modern” technologies such as real-time PCR into their food testing repertoire. The food industry is cognizant of the fact that standard microbiological techniques offer much slower time-to-results than can be obtained by real-time PCR, (culture-based Salmonella detection takes at least 4 d to complete whereas real-time PCR can detect the presence of bugs within an hour or two), and are always looking for ways to speed up the safety inspection process. Nonetheless, before safety inspectors jump on the real-time PCR bandwagon, they will require that the wrinkles inherent in some real-time PCR analysis kits (such as the detection of false positives) be ironed out before the they are used on a routine basis. Well, the time for switching techniques may be near.
In a study published in the Journal of Food Science Investigators from the Division of Food Systems and Bioengineering at the University of Missouri have employed the use of Ethidium bromide monoazide (EMA) to bind to DNA of dead cells and prevent its amplification by PCR thereby eliminating detection of dead cells when testing Salmonella levels in chicken and eggs. While PCR cannot differentiate between DNA from live and dead cells (thus posing a problem if used as a technique for quantifying live cells only in a mixture of live and dead cells), EMA staining step prior to PCR allows for the effective inhibition of false positive results from DNA contamination by dead cells.
Modifications to real-time PCR techniques such as the one described above will certainly enhance the uptake of PCR in food safety testing cutting down on manufacturers time to market thereby increasing their profits.
This news comes just in time for Sonya “black widow” Thomas the new buffalo wing eating champion who weighing in at just 105 pounds, beat out professional eating champion Joey Chestnut (231 pounds) by consuming 181 chicken wings in 12 minutes in the 9th annual National Buffalo wing Festival in Buffalo, NY. Faster food safety testing of chicken wings should translate into more wings available for Sonya to consume in the next gluttonous competition!