In a recent study, the U.S. Centers for Disease Control and Prevention (CDC) has identified non-typhoidal Salmonella (NTS) as one of the top five pathogens contributing to foodborne illnesses in the U.S. Cases of salmonellosis were largely associated with beef products, despite implementation of interventions at slaughter and processing facilities to reduce contamination.
For its analysis, CDC collected data from its Foodborne Disease Outbreak Surveillance System (FDOSS), searching for all foodborne NTS outbreaks linked to beef as the single contaminated ingredient or implicated food, with the date of first illness onset spanning 2012–2019. Data provided by FDOSS included number of illnesses, hospitalizations, deaths, patient demographics, outbreak duration and geographic scope, method and setting of food preparation, traceback and recall information, and NTS serotypes for each outbreak. The researchers also queried CDC’s National Antimicrobial Resistance Monitoring System (NARMS) for information on antibiotic susceptibility testing for outbreak-related isolates identified through FDOSS.
Considering individual beef processing categories and Salmonella serotypes, CDC researchers calculated the number of outbreaks, outbreak-related illnesses, hospitalizations, and total deaths. During 2012–2019, 27 Salmonella outbreaks were linked to beef consumption, resulting in 1,103 illnesses, 254 hospitalizations, and 2 deaths. The most common category implicated was non-intact raw beef (12 outbreaks, or 44 percent), followed by intact raw beef (6 outbreaks, or 22 percent). Ground beef was responsible for the most illnesses (800 illnesses, or 73 percent) and both of the reported deaths, and was the source of the largest outbreak.
Additionally, antimicrobial resistance (AMR) data were available for 717 isolates from 25 outbreaks. Nine (36 percent) of these outbreaks involved isolates that were resistant to one or more of the antibiotics tested by NARMS, of which eight (89 percent) contained multidrug resistant isolates.
According to the researchers, the findings stress the importance of prevention strategies at the pre-harvest stage, such as bovine vaccination and biosecurity management practices. There is also a need to study further the role that dairy versus beef cattle play in harboring Salmonella and the contamination of ground beef resulting in human illness to help identify potential public health interventions at the pre-harvest level.
The study also found that foodborne illness outbreak investigators were rarely able to trace implicated beef to a single processing or slaughter facility, let alone trace it back to the farm level, hindering prevention efforts. The opportunity to trace cattle from slaughter back to source farms would better allow investigators to identify a common farm or farms, and work with animal health experts to identify on-farm prevention opportunities.
Overall, the study underlines that a multi-layered approach is required to ensure food safety and reduce foodborne illness incidence. At retail, understanding purchasing behaviors and consumers’ knowledge about preparation, as well as the availability and benefits of post-harvest interventions like irradiation, can expose gaps where interventions can be applied. During slaughter and processing, further research into the role lymph node removal plays in reducing harmful bacteria is warranted. Finally, at the farm level, biosecurity and vaccination are two prevention strategies under investigation to promote herd health.
