Fighting Against Food Pathogens

In the world of virulent foodborne pathogens, Campylobacter and Salmonella have become the chief culprits, responsible for nearly 70 percent of all such illnesses in the U.S. last year. Detecting these and other bacteria in the food supply is a matter of growing urgency for both government regulators and the food industry. As the food chain expands globally, manufacturers are being held increasingly responsible for preventing outbreaks under the Food Safety Modernization Act (FSMA).

“We are making progress in detecting and responding more quickly to foodborne illness, but our priority remains preventing illnesses from happening in the first place,” says Susan Mayne, PhD, director of FDA’s Center for Food Safety and Applied Nutrition (CFSAN).

Campylobacter is commonly associated with consumption of raw or undercooked poultry and meat, while Salmonella is an issue in many types of food, including eggs, meat, poultry, fruits, vegetables, spices, and nuts. Both bacteria can cause mild to severe illness, from uncomplicated diarrhea to severe systemic infections, such as Guillain-Barré syndrome (Campylobacter), an autoimmune disease that can cause paralysis, and reactive arthritis (Salmonella), which can cause acute, debilitating joint pain.

“In order to decrease the likelihood of these pathogens in the food chain, it is essential to analyze the raw material, the environment where the food is produced, and food products at different manufacturing stages; for example niches where Salmonella could be harbored in the environment that could cause cross-contamination,” says Claudia Narvaez, PhD, professor of food science at the University of Manitoba, Canada.

Advances in laboratory and onsite testing equipment are allowing manufacturers to more easily and economically sample their raw ingredients, environment and facilities, and finished products for evidence of bacterial contamination, thus greatly reducing the potential for a recall, or worse. These developments include time-of-flight mass spectrometry, bacteriophage-based assays, novel biosensors, as well as advances in traditional techniques, such as polymerase chain reaction (PCR).

“Test methods continue to improve, with many methods now available that give results within 24 hours of sample receipt by the lab,” explains Timothy Freier, PhD, vice president for scientific affairs and microbiology at Mérieux NutriSciences (North America). But he also urges caution. “With these faster turn-around times, test methods are walking the line between incubation time and detection capabilities, so careful validation of these ultra-rapid methods is crucial,” Dr. Freier tells Food Quality & Safety magazine.

Accurately detecting and eliminating pathogens is increasingly essential for industry because advances in whole genome sequencing (WGS) are allowing public health agencies and government regulators to identify and trace foodborne contamination, such as Salmonella, back to specific growers and processing plants with increasing accuracy, faster and more cheaply than ever before.

“This is raising the bar for the food industry, as new food-illness associations are found,” Freier adds. “A combination of ingredient testing, finished product testing, and environmental monitoring are typically needed to control this hazard.”

Illnesses and Deaths

While exact numbers remain unknown, the CDC has estimated that about 48 million people in the U.S. get sick from a foodborne illness, 128,000 are hospitalized, and 3,000 die annually. The World Health Organization notes that Campylobacter is the world’s most common foodborne bacterial cause of diarrhea, responsible for more than 95 million illnesses and 21,000 deaths annually, according to a 2015 report.

In 2016, surveillance from labs in 10 U.S. states confirmed about 24,000 foodborne infections, more than 5,500 hospitalizations, and nearly 100 deaths caused by nine enteric pathogens commonly transmitted through food, according to the CDC’s latest Foodborne Diseases Active Surveillance Network (FoodNet) report, published in April.

Among the bacteria, Campylobacter and Salmonella led the pack, being responsible for 8,547 and 8,172 illnesses, respectively. The remaining pathogens were distant finishers, from Shigella (number three on the list with 2,913 illnesses) to the parasite Cyclospora (number nine with only 55 illnesses). While Listeria was close to the bottom in terms of prevalence (127 cases) it was the most virulent of all, with 97 percent of its victims requiring hospitalization and 13 percent of them dying.