3M Microbiology can now provide its customers with an environmental Listeria test that allows them to improve their Listeria monitoring programmes. The 3M™ Petrifilm™ Environmental Listeria Plate helps to increase the quality and quantity of information from tests making it possible to detect, track and manage environmental Listeria with greater efficiency.

The Petrifilm Environmental Listeria (EL) plate is a sample-ready culture medium containing selective agents, nutrients, a cold-water-soluble gelling agent, and a chromogenic indicator that facilitates Listeria colony detection. The benefits of using our new Petrifilm Environmental plates are:

• More frequent testing, without increasing your budget
• Detect the presence of Listeria, allowing you to take informed and precise action
• Perform Listeria tests WITHOUT enrichment - giving the option to test 'in-house', saving money and receiving more timely results
• Allows you to more aggressively test the plant environment
• Can be interpreted quantitatively, giving more information to help you identify hot spots and contamination sources, and take appropriate action
• Provides rapid results in <32 hours from sample collection
• Has an easy-to-use procedure, a familiar Petrifilm plate format, and requires no additional equipment

Petrifilm EL plates were designed to analyse environmental samples and help increase the efficiency of monitoring plant sanitation. The presence of indicator Listeria sp.such as Listeria innocuaprovides evidence that environmental conditions are suitable for the occurrence of Listeria monocytogenes. The Petrifilm EL plate detects the majority of environmental Listeria, consisting of Listeria monocytogenes, Listeria innocua, and Listeria welshimeri.

Many organisms in the environment can be stressed by environmental conditions or sanitisers. Buffered peptone water (BPW) is used as a repair broth in conjunction with the Petrifilm EL plate to resuscitate stressed Listeria without increasing their numbers. Repair in BPW is not an enrichment step. It may be used as a qualitative, semi-quantitative, or quantitative test.

• A qualitative interpretation may be desired if presence/absence is sufficient and appropriate.
• A semi-quantitative interpretation may be desired if different actions will be taken depending on the relative level present, and/or if recording actual numbers is not desirable. The assigned category (e.g., high/medium/low or unacceptable/marginal/acceptable) is dependent upon your sampling location and your individual plant standard.
• A quantitative interpretation may be desired if different actions will be taken based upon the number of colonies present. The Petrifilm EL plate's quantitative results will allow you to monitor any significant changes in environmental Listeria levels and take informed and precise action.