Standards for Detection and Enumeration of Listeria monocytogenes and Listeria spp. in the food chain

Listeria monocytogenes is one of the most virulent foodborne pathogens, responsible for an increasing amount of deaths worldwide annually. Listeriosis is the major cause of death among foodborne bacterial pathogens.

Infections by Listeria monocytogenes can happen in any stages of food processing. Listeria monocytogenes can be found in the fecal matter, soil and waste waters. It is also found in the intestinal tract of many animals including mammals, birds, fish, insects, reptiles. As such it easily gets into the food chain as a contaminant of raw food.
Whilst it is killed by heat processes such as pasteurisation it is innately resistant to harsh environmental conditions e.g. it survives low pH, high salt and can grow at refrigeration conditions as well as producing biofilms. This can result in it persisting in food processing environments with the potential to contaminate foods. Foods that receive no further cooking or heat treatments such as ready-to-eat foods are an issue.
When Listeria is detected as part of monitoring, even if it is low levels below the legal limit, the source contamination should be investigated as L. monocytogenes can persist in food processing environments for several years. Factory hygiene in general is important, particularly cleaning of equipment - equipment should be able to be dismantled for thorough cleaning.

Standards for Detection and Enumeration of Listeria monocytogenes and Listeria spp. in the food chain

The International Organization for Standardization (ISO), published revised EN ISO 11290-1 and EN ISO 11290-2 standards in 2017. In Part 1, a horizontal method for the detection of Listeria monocytogenes and Listeria spp. is specified, and in Part 2, the enumeration of these organisms in food, animal feed and environmental samples is described. The revised Part 1 edition cancels and replaces the first edition EN ISO 11290-1:1996 and incorporates the amendment 1 from 2004. Part 2 cancels and replaces the first edition of EN ISO 11290-2:1998 and incorporates the amendment 1 from 2004. Compared to the previous edition, the main changes are considered as major. In the revised EN ISO 11290:2017, the scope in both Parts 1 and 2 has been extended to enable also the detection and enumeration of Listeria spp.

Listeria monocytogenes and Listeria spp. detection according to the EN ISO 11290-1:2017 standard
The main changes, compared to ISO 11290-1:1996, are the following:
— Scope extended to include Listeria spp. detection. The title has changed accordingly.
— Primary enrichment in half-Fraser broth: incubation for 25 h ± 1 h.
— Secondary enrichment in Fraser broth: incubation for 24 h ± 2 h.
— Half-Fraser and Fraser broths may be refrigerated before transfer or isolation on selective agar for a maximum of 72 h.
— Storage of isolation plates: incubated plates can be refrigerated for a maximum of two days before reading.
— Microscopic aspect for confirmation is optional if the isolation agar allows distinction between pathogenic and non-pathogenic Listeria spp.
— CAMP test and catalase test are optional.
— Inclusion of new performance characteristics.

Listeria monocytogenes and Listeria spp. enumeration according to the revised EN ISO 11290-2:2017 standard
The main changes, compared to ISO 11290?2:1998, are the following:
— Enumeration of Listeria spp. is included in the scope. Title is changed accordingly.
— Primary suspension with buffered peptone water, half-Fraser broth with or without supplements, and all appropriate diluents referred to in ISO 6887 (all parts).
— Resuscitation step (incubation of initial suspension of sample 1 h ± 5 min at 20 °C ± 2 °C) deleted.
— Microscopic aspect, catalase and CAMP test for confirmation are optional.
— Inclusion of new performance characteristics.

Compliance to revised ISO 11290:2017
We have implemented all the requirements described in both part 1 and part 2 of the revised EN ISO 11290:2017.
Our dehydrated culture media, ready-to-use media in agar plates, tubes, bottles, bags are all compliant with EN ISO 11133:2014. All information regarding the reference standard compliance are indicated in the product technical sheets, available on our website.

Check our products for Listeria monocytogenes and Listeria spp.:

MOPS Buffered Listeria Enrichment Broth

Morpholinepropanesulfonic acid-buffered Listeria enrichment broth (MOPS-BLEB) is a selective liquid medium used for the isolation and identification of Listeria monocytogenes from food, i.e. red meat, poultry, egg products, and fish, and environmental samples, according to the USDA-FSIS method.

MOPS Buffered Listeria Enrichment Broth
20 tubes x 10 mL
ref. 24489

Contam Swab Listeria (ref. 86102) is a swab based test with culture media for easy microbial count and identification directly from environmental surfaces. 

Benefits

• Easy to use
• Clear color changes
• No additional reagents
• Results in 18/24 hours
• 10 CFU/mL detection limit 

Listeria System 18R (ref. 71640) is a gallery for the biochemical identification of Listeria spp. (Listeria monocytogenes, Listeria innocua, Listeria ivanovii, Listeria seeligeri, Listeria welshimeri, Listeria grayi sub. grayi, Listeria grayi sub. murrayi, Jonesia denitrificans ).

Benefits

• Complete identification
• Cost effective
• Results in 18-24 hours
• Clear and well defined color changes
• Easy interpretation, visually or by automated readers 

Liofilchem’s Food System (ref. 71680) is an innovative solution, validated to ISO 16140 for Listeria monocytogenes and Salmonella spp. detection, that can simplify the workflow of your microbiological testing laboratory: https://www.liofilchem.com/en/products/featured-products/food-system.html

We also produce the freeze-dried CultiControl™ pellets for Quality Control and Quanti-CultiControl™ for Growth Promotion Testing, Microbial Limits Testing, Microbial Enumeration Testing: