Like it or not, congratulations are in order for Campylobacter. This ubiquitous organism captured first place honors on the CDC’s list of organisms responsible for foodborne illness in the U.S. in 2016, with 8,547 cases reported on CDC’s Foodborne Diseases Active Surveillance Network (FoodNet).
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In addition to this overall number of reported campylobacteriosis cases, Campylobacter ranks among foodborne pathogens as the third leading cause of hospitalizations (with 1,082 out of 5,512 hospitalizations, 19 percent of hospitalizations) and the fifth leading cause of death (10 deaths attributed to Campylobacter out of 98 deaths attributed to all foodborne pathogens) in the U.S. in 2016, according to FoodNet’s April 21, 2017 issue of the Morbidity and Mortality Weekly Report.
To track foodborne infections and identify potential sources of infection, the CDC’s FoodNet program collects data from sites in 10 states that test samples for foodborne pathogens. Together, FoodNet sites cover approximately 15 percent of the U.S. population.
The aforementioned FoodNet report shows that Campylobacter and Salmonella (8,172 cases) were the leading cause of foodborne infections in 2016, followed by Shigella (2,913 cases), Shiga toxin-producing Escherichia coli (1,845 cases), and Cryptosporidium (1,816 cases). (Yersinia, Vibrio, Listeria, and Cyclospora were also reported, but with about 300 or fewer cases each.)
Of note, this is the first time the report includes in the total number of infections in FoodNet sites those foodborne bacterial infections diagnosed only by rapid diagnostic tests, which are described collectively as culture-independent diagnostic tests (CIDTs).
Previously, the report counted foodborne bacterial infections confirmed only by traditional culture-based methods in the total numbers.
Of the 8,547 total 2016 Campylobacter cases, 5,782 cases were confirmed with culture and 2,765 cases were detected via CIDT alone.
According to CDC, CIDTs, which work by detecting the presence of a specific antigen or genetic sequence of an organism, are increasingly used for diagnosing intestinal bacterial infections transmitted commonly by food.
Since CIDTs do not require isolation and identification of living organisms, they can be conducted more rapidly and yield results sooner than can be achieved with traditional culturing methods, says Robert Tauxe, MD, director of CDC’s Division of Foodborne, Waterborne, and Environmental Diseases.
Dr. Tauxe is quick to point out that, while CIDTs can have immediate benefits for treatment, they don’t collect information needed to determine if an infection is antibiotic-resistant or if it is linked to an outbreak. And, while positive results on rapid tests can be followed up by culture-based tests to get detailed data, they often are not.
“Public health officials need foodborne-illness trend data to monitor progress toward making our food supply safer,” Dr. Tauxe emphasizes. “Thus, it’s important that laboratories continue to do follow-up cultures on CIDT-positive patients.”
The shift to CIDTs poses challenges to monitoring foodborne illness trends, Dr. Tauxe says, because changes in the number of new infections could reflect changes in testing practices rather than a true increase in infections. “For this reason, comparisons of the 2016 data with data from previous years may not accurately reflect trends,” he emphasizes. “Current estimated infections and those from years past are accurate, but cannot be directly compared because the total now includes results from culture-independent diagnostic tests.”
Beyond reported cases, Campylobacter causes an estimated 1.3 million illnesses each year in the U.S.
“Figuring out where an infection came from can be challenging, but we think Campylobacter infections most often follow eating undercooked poultry, or other foods that the raw poultry dripped on,” Dr. Tauxe relates. “Infections can also follow contact with pets, or drinking raw milk. Cooking poultry to 165 degrees Fahrenheit, being careful not to let raw poultry contaminate other foods, and pasteurizing milk can help keep people well.”
Whole Genome Sequencing
Starting in 2018, the CDC plans to begin using whole genome sequencing (WGS) in the PulseNet network to “fingerprint” Campylobacter (and also Salmonella and E. coli), according to Dr. Tauxe. This work flows from the pilot program CDC launched in 2013 to implement WGS for Listeria subtyping and control.