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Listeria monocytogenes Contamination in Ready-to-Eat (RTE) Meats

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The presence of Listeria monocytogenes, an environmental pathogen, poses significant risks to consumers. This bacterium, found in soil, water, and decaying vegetation, can contaminate various foods, potentially leading to mild listerial gastroenteritis or severe listeriosis, which carries a notably high mortality rate compared to other foodborne illnesses. Vulnerable populations such as pregnant women, the elderly, and individuals with weakened immune systems face the most significant risk of listeriosis from consuming contaminated foods[1].

Contamination often occurs during food processing or packaging, with refrigerated ready-to-eat (RTE) meats being particularly susceptible due to L. monocytogenes resilience to cold temperatures. Currently, only a select few countries, including the United States and Turkey, enforce a "zero tolerance" policy for L. monocytogenes in RTE foods, mandating non-detection of the bacterium in 25 grams of product[2].

The largest and most deadly outbreak of listeriosis recorded globally to date was linked to  RTE meat products known as polony in South Africa between 2017 and 2018. The outbreak resulted in hundreds of confirmed cases and numerous fatalities. Continued efforts are needed to develop robust mitigation strategies against virulent and emerging strains of L. monocytogenes[2].

Formulating RTE meats to inhibit L. monocytogenes growth is crucial in reducing listeriosis risk. Factors such as low pH (≤4.4), low water activity (≤0.92), and the use of antimicrobial substances during production can effectively impede bacterial growth[1]. Additionally, implementing stringent manufacturing practices and preventive controls, as outlined by Good Manufacturing Practices (CGMPs) and Preventive Controls for Human Food (PCHF) requirements, is critical. These measures encompass controlling raw materials, employing listeriacidal measures, maintaining sanitation, and implementing environmental monitoring programs to prevent post-processing contamination.

In conclusion, addressing L. monocytogenes contamination in RTE meats requires a comprehensive approach. Our team at Mérieux NutriSciences stands ready to assist you in this endeavor by offering a range of services tailored to your needs.

We can design and execute inoculated challenge studies to test your formulations for L. monocytogenes growth, ensuring the efficacy of your mitigation strategies. Additionally, we provide validation services for your cook step to guarantee the lethality of pathogens, which is essential for ensuring food safety.

Furthermore, our experts offer training for your plant personnel on the regulatory requirements specific to RTE meats, empowering your team to uphold the highest food safety standards. We can also assist in developing robust food safety plans and management systems that meet regulatory requirements and ensure compliance.

To safeguard your facility against contamination, our environmental monitoring services provide ongoing surveillance, identifying potential risks and enabling prompt intervention. Additionally, routine testing of your products and environmental samples ensures ongoing monitoring and early detection of any issues.

With our comprehensive suite of services, you can rest assured that your RTE meat products are in safe hands. Contact us today to learn how our meat industry services can support your food safety initiatives and protect your brand reputation.


[1] Control of Listeria monocytogenes in Ready-To-Eat Foods: Guidance for Industry Draft Guidance. (n.d.).

[2] Listeria monocytogenes in ready-to-eat (RTE) foods: attribution, characterization and monitoring. (2022). In Listeria monocytogenes in ready-to-eat (RTE) foods: attribution, characterization and monitoring. FAO; WHO; 

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