When it comes to problematic pathogens that impact the meat and poultry industry, Listeria monocytogenes is among the most persistent.
Listeria is a particularly virulent pathogen. According to the US Centers for Disease Control and Prevention (CDC), about 1,600 people in this country get listeriosis each year, with a hospitalization rate of 94% and an annual death rate of about 260.
Foodborne illness outbreaks and recalls due to concerns about L. monocytogenes continue to make headlines and potentially erode confidence in the safety of meat and poultry products, especially in ready-to-eat meats. Already this year, a multi-state outbreak of Listeria was tied to deli meat products and there were several product recalls in 2020 due to possible Listeria contamination.
On the positive side, there have been improvements in the control of this species of pathogenic bacteria in meat and poultry products.
“The industry has made some dramatic improvements in the control of Listeria in ready-to-eat meats. If you look at the results from USDA’s testing programs, it is clear that the industry took the matter seriously and took the necessary steps to control the issue,” said James Dickson, professor, department of animal sciences at Iowa State University, Ames, Iowa.
Those steps are ongoing, with collaborative efforts from meat and poultry processors, researchers, academic research and government. The Food Safety Modernization Act (FSMA), for example, includes clearer guidance for food manufacturers on preventive measures to control L. monocytogenes in their environments, while the US Department of Agriculture (USDA) focuses on a “seek-and-destroy” approach with stringent best practices. In late 2020, the Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO) met and identified key gaps in the current FAO/WHO risk assessment model and highlighted principles to be considered for risk assessment for L. monocytogenes.
Going forward, Listeria detection and prevention should still be top of mind, given the virulence of the pathogen, Dickson pointed out. “In my personal opinion, the biggest vulnerability is complacency. It seems as if many establishments have very effective environment sanitation and monitoring programs, and there is a tendency to think that we have ‘solved’ the Listeria issue. Listeria hasn’t gone away, and if we relax our programs, we have the potential to get into trouble. I think that the hardest part of this is to maintain continued vigilance when it seems as if the problem is under control,” he said.
Matt Henderson, director of food safety for Land O’Frost Inc., Lansing, Ill., agrees. “Listeria is ever-present in the environment surrounding our facilities and will be always be a hazard we must make every effort to control. Our understanding of how to control it has increased tremendously over the past two decades. Improvements in sanitary design of facilities and equipment have played a large role in that success. And industry efforts to share Listeria control best practices have also been a significant contributor to the reduction of Listeria positives in meat and poultry products,” he said. “Maintaining that awareness and avoiding complacency in our programs must be an ongoing focus for organizations to prevent what continues to be a significant food safety risk.”
Steven Tsuyuki, senior director, corporate sanitation, Maple Leaf Foods, Mississauga, Ontario, likens it to an ongoing battle on several fronts.
“Processors today must take a multiple hurdle approach to control Listeria that focuses on the key control factors including GMPs, controlled traffic, keeping floors dry and uncracked floors, scrupulous sanitation and sanitary design of equipment and facilities. In addition, plants must implement an aggressive environmental monitoring program with a Seek-and-Destroy process that is collaborative and unrelenting,” he said.
Tools and technologies
Keeping Listeria top of mind and in check can be enhanced with advances in detection and control. Better technologies are emerging at a time when there is still a need to tighten measures.
Stemming spread before it starts, testing technologies are crucial. Tsuyuki emphasizes advancements in results and source identification.
“The turnaround time for results can now be measured in hours versus days and this enables us to act more quickly to prevent and address problems,” Tsuyuki said. “In terms for source identification, technologies today are capable of strain identification that enables the linkage of foodborne outbreaks to the source where they were produced. Rapid, comprehensive information is such an important tool in Listeria prevention.”
Tsuyuki also underscored the importance of environmental sampling.
“Routine environmental sampling provides a ‘voice of the process’ that product testing does not provide,” he pointed out.
Land O’Frost also focuses on improved detection capabilities.
“Developments in molecular detection technology have increased the sensitivity and reliability of Listeria testing available to industry. Along with improvements in testing methods themselves, there have been technological improvements in the tools used to collect Listeria samples from our plant,” Henderson said.
He cites some examples that have impacted detection.
“Materials used in the construction of environmental sampling sponges have changed to facilitate recovery of microorganisms. The neutralizing buffers used in the sample collection kits have also evolved to promote recovery and adapt changing sanitizers used by industry,” he said. “Finally, the technology used to coordinate sample collection and analyze data has changed. Software programs are now available to manage the scheduling of sample collection in increasingly complex programs. The same software contains advanced tools to track and trend sample results greatly reducing the time required for data analysis.” Among other measures, Land O’Frost has shifted its focus outward to Zone 4 and sites that measure the effectiveness of interventions like boot scrubbers for employee traffic.
Suppliers of testing tools and mechanisms have continually improved upon capabilities to seek and destroy Listeria. PerkinElmer, for example, offers state-of the-art testing solutions, including ELISA-based kits for rapid detection in both food and environmental samples and a system that allows labs to batch hundreds of samples with walkaway automation.
That’s especially helpful in and beyond the pandemic, which has accelerated a trend toward automation in processing plants and labs alike, said Paul Morrison, portfolio director, food end markets and microbiology. “Food processors must react with urgency to positive Listeria results in their facilities. Diagnostic technology advances, such as the next day Solus One system from PerkinElmer, have dramatically reduced the lag time between production lots and obtaining test results, enabling more rapid preventive actions,” he said.
Other technologies help uncover vulnerabilities for processors, including those who make ready-to-eat products. Scientists at Cornell University, for instance, have created a computer program that can predict areas of a product facility in which the pathogen is most likely to be found. Given the fact that meat and poultry plants are complex in terms of equipment, processes and employees, the ability to determine optimal locations for environmental monitoring is valuable.
In addition to sampling, there have been other improvements in technologies aimed at L. monocytogenes control. In late 2020, the Journal of Environmental Chemical Engineering reported that researchers at the University of Houston found that cobalt-doped titanium-dioxide (CoO-TiO2) stops the reproduction of Listeria monocytogenes in both light and dark conditions, opening the door to controlling the pathogen in food products that are sealed and light-protected. While this may stop Listeria, testing will have to be done to confirm safety in food products and food production environments.