Food Microbiology Marches On

Attention to pathogens has paid off. Foodborne pathogens are responsible for some 76 million illnesses in the United States annually. But the incidence of E. coli O157:H7, one of the most severe foodborne diseases, declined 36% from 2002 to 2003, according to a report by the Centers for Disease Control and Prevention (CDC) and others. The overall incidence of E. coli O157:H7 has declined 42% since 1996. The data also showed that the incidence of three common foodborne diseases—Campylobacter, Salmonella, and Yersinia—continued to decline substantially over the previous eight years. The declines were attributed to enhanced surveillance and outbreak investigations to identify new control measures. More attention was also placed on disease prevention.

Starting in 1997, the USDA’s Food Safety and Inspection Service implemented the Pathogen Reduction/Hazard Analysis Critical Control Point (HACCP) system in all 6,000 federally inspected meat, poultry, and egg products plants over a three-year period. In addition, in 1996, the CDC, USDA, and FDA established the Foodborne Diseases Active Surveillance Network (FoodNet) surveillance system to quantify, monitor, and track the incidence of laboratory-diagnosed cases of foodborne illnesses.

“The public health case is driving food microbiology now,” said Dr. Zink. He added that FoodNet and PulseNet, a national network of public health and food regulatory agency laboratories coordinated by the CDC, have improved scientists’ ability to identify a pathogen and the specific food that carries it. It is more than a thousand times better than was possible even a decade ago, he said.

Faster Turnaround

With millions of dollars and reputations at stake during recalls, there is a push toward more rapid test results. In comparison with earlier methods, which could take up to a week, some results are now available within eight hours—a factory shift. “The purpose is to do one-shift tests,” said Daniel Fung, PhD, professor of food science at Kansas State University in Manhattan, Kan. Dr. Fung, a member of the Food Quality editorial advisory board, pioneered a method to miniaturize a most probable number system that can test for pathogens within a single factory shift.

The incidence of E. coli O157:H7, one of the most severe foodborne diseases, declined 36% from 2002 to 2003, according to a report by the Centers for Disease Control and Prevention and others. The overall incidence of E. coli O157:H7 has declined 42% since 1996.

The food industry has followed some of the test techniques used in the pharmaceutical industry, but that can be challenging. Molecular techniques in the clinical industry may not always be appropriate in the food industry because the latter has such low margins, said Morgan Wallace, PhD, senior research microbiologist at DuPont Qualicon in Wilmington, Del.

DuPont offers a PCR-based system called BAX that came out of clinical diagnostics in the mid 1990s, when assays for the food industry could be developed. The company has 13 PCR assays that target nine microbes. DuPont has sped up results by taking measurements at the end of each PCR cycle instead of at the end of each batch. The result is that after E.coli is enriched for about eight hours, results are available in about 55 minutes, compared to 3.5 hours using the prior method. And BAX can detect multiple species in parallel in one PCR reaction.

Strategic Consulting’s Weschler believes the food industry is pushing ahead of pharma with rapid methods. “The food industry is further along in rapid methods than pharma, and it is driving new methods,” he said. Dr. Bailey of bioMerieux is not as optimistic. “It will be a long time before we can significantly shorten” the test result time, he said.