Detection of Listeria monocytogenes

Introduction

Listeria monocytogenes is a species of pathogenic bacteria that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. Listeriosis is a serious infection that can cause fever, muscle aches, headache, nausea, vomiting, and diarrhea. In some cases, it can lead to more serious complications, such as meningitis, miscarriage, and stillbirth.

detection-of-listeria-monocytogenes https://link.springer.com/article/10.1007/s00203-021-02590-2

Listeriosis in foods

Listeriosis can be caused by eating food contaminated with Listeria monocytogenes. This bacterium can contaminate a variety of foods, including.

listeria-in-foods https://foodmicrobiology.academy/2021/08/10/be-aware-of-listeria-monocytogenes/

Raw milk and soft cheeses made from unpasteurized milk
Deli meats and hot dogs
Smoked fish
Raw fruits and vegetables
Cooked meats that have been contaminated after cooking

Source of contamination

Listeriosis contamination can occur at any point in the food production process, from farm to table. Some possible sources of contamination include:

Contaminated water used in irrigation or food processing
Contaminated soil
Animals that carry the bacteria
Food processing equipment that is not properly cleaned and sanitized

Importance of testing

The detection of Listeria monocytogenes in foods is crucial for several reasons:

Importance	Description
Public health protection	Detecting Listeria helps prevent outbreaks of listeriosis, a serious illness that can be life-threatening for high-risk individuals.
Food safety and quality control	Identification of Listeria contamination allows removal of contaminated products before they reach consumers, protecting the food supply chain.
Improved food safety practices	Detection methods encourage stricter hygiene protocols, proper storage/handling, and environmental monitoring in food processing facilities.
Traceability and source identification	Detection helps trace the source of contamination, pinpoint root causes, and implement targeted interventions to prevent future outbreaks.
Regulatory compliance	Efficient detection methods ensure compliance with regulations mandating Listeria testing in certain foods, maintaining consumer confidence in food safety.
Importance	Description
Public health protection	Detecting Listeria helps prevent outbreaks of listeriosis, a serious illness that can be life-threatening for high-risk individuals.
Food safety and quality control	Identification of Listeria contamination allows removal of contaminated products before they reach consumers, protecting the food supply chain.
Improved food safety practices	Detection methods encourage stricter hygiene protocols, proper storage/handling, and environmental monitoring in food processing facilities.

Recent recall

Recent outbreaks and recalls highlight the importance of monitoring and controlling Listeria monocytogenes in the food supply chain. For instance, in 2024, the FDA released a list of retailers that received tainted products linked to an outbreak of Listeria Monocytogenes from Rizo Lopez in Fresno, California.This outbreak had sickened 26 people, hospitalized 23, and resulted in two deaths across 11 states. The recalled products included a wide range of items, such as cheese, dips, salad dressings, enchiladas, and more, sold under various brands
Costco issued a recall in February 2024 for two products that contained ingredients from Rizo Lopez Foods - the Southwest Chicken Wrap with Sauce and the Chicken Street Taco Kit from their Service Deli. These products were sold between October 2023 and February 2024

Standards and Regulations

Region	Standards/Regulations	Key Points
European Union (EU)	Commission Regulation (EC) No 2073/2005 on microbiological criteria for foodstuffs	* Focuses on Ready-to-Eat (RTE) foods * No tolerance for Listeria in RTE that support its growth * Alert level (100 CFU/g): Requires investigation and corrective actions * Aligned with Codex Alimentarius standards
United States (US)	* Federal Food, Drug, and Cosmetic Act (FD&C Act) * USDA Food Safety and Inspection Service (FSIS) Compliance Directive 1022.45	* Zero tolerance for Listeria monocytogenes in RTE meat products * Emphasis on preventive measures and post-processing controls * Differs from EU approach in terms of specific limits
India	* Prevention of Food Adulteration Act, 2015 (PFA Act) * FSSAI (Food Safety and Standards Authority of India) Guidelines for Listeria monocytogenes in Foodstuffs (2010)	* L. monocytogenes absence in RTE foods is recommended * Alert level (100 CFU/g): Requires investigation and corrective actions * Standards under development, referencing Codex Alimentarius

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02005R2073-20140601&from=DA
https://www.fda.gov/files/food/published/Draft-Guidance-for-Industry--Control-of-Listeria-monocytogenes-in-Ready-To-Eat-Foods-%28PDF%29.pdf
https://www.fssai.gov.in/upload/uploadfiles/files/pfa-acts-and-rules.pdf

Analyses for Listeria monocytogenes Detection

Culture Enrichment: This is the primary method for detecting Listeria monocytogenes in food products. It involves taking a sample of the food and enriching it in a special broth that allows Listeria to grow while inhibiting the growth of other bacteria. After enrichment, the sample is streaked onto a selective agar plate that allows for the identification of Listeria colonies.
PCR (Polymerase Chain Reaction): PCR is a rapid and specific method for detecting Listeria monocytogenes. It can be used to confirm the presence of Listeria after culture enrichment. PCR works by amplifying a specific DNA sequence of Listeria monocytogenes.
Immunoassays: Immunoassays are another rapid method for detecting Listeria monocytogenes. They work by detecting antibodies that bind to Listeria antigens. Immunoassays can be used to screen for Listeria in food samples.

Eurofins services in detection of Listeria monocytogenes

Eurofins offers various services to detect Listeria monocytogenes, a bacterium causing foodborne illness. These services include:

Traditional culture methods: This standard method involves culturing a sample of food or environmental material in a special medium for Listeria growth. After incubation, the sample is examined for Listeria colonies.

Rapid PCR methods: PCR (polymerase chain reaction) is a faster method detecting Listeria DNA in a sample within 24 hours. However, PCR doesn't determine if the Listeria is alive or dead. Therefore, a positive PCR test requires confirmation with a culture method.

Eurofins also provides environmental monitoring services to identify and control Listeria in food processing facilities, helping prevent foodborne illness outbreaks. The best Eurofins service for you depends on your needs. If you're concerned about Listeria in a food product, a traditional culture method or rapid PCR might be suitable. If you're interested in preventing Listeria contamination in your food processing facility, environmental monitoring services might be a good option.

References

Osek, J., Lachtara, B., & Wieczorek, K. (2022). Listeria monocytogenes in foods—From culture identification to whole-genome characteristics. Food Science & Nutrition, 10(9), 2825-2854. https://doi.org/10.1002/fsn3.2910
https://abcnews.go.com/GMA/Food/recalled-dairy-products-linked-listeria-outbreak-7-states/story?id=106991310
https://www.foodsafetynews.com/2024/02/fda-releases-list-showing-hundreds-of-retailers-that-received-tainted-products/