SMT LABS Official: Listeria protocol and notification

At SMT LABS we provide fast and efficient service and testing for the detection of Listeria monocytogenes in food and swabs.  Products include: Meat and meat products, Poultry and poultry products, Spice, Egg and egg products, Vegetables and fruits, Dairy and dairy products, Grain and grain products.

1. Listeria species

The genus Listeria contains six species, namely L. grayi, L. innocua, L. ivanovii, L. seeligeri, L. welshimeri and L. monocytogenes. Although L. ivanovii and L. monocytogenes can cause illness in mice and other animals, it is only L. monocytogenes that is associated with human Listeriosis. If any of the other strains (non-pathogenic to humans) are detected in a product or facility, it indicates that the environment and nutritional conditions are favourable for the growth of the pathogenic strain, L. monocytogenes and that precautions should be taken.

2. Types of Testing

There are two tests that can be performed to determine if a product contains Listeria monocytogenes.
The first is detection, which is a qualitative test that provides a positive/negative answer for the absence/presence of Listeria monocytogenes in 25g of product. For this test the sample is incubated overnight in an enrichment broth to enable multiplication of the bacteria for further isolation tests. The detection test is more sensitive and can detect lower numbers of the organism as compared to enumeration.

The second test is enumeration (count) and is a quantitative test to determine the number of bacteria present in 1g of product. For this test a representative sample is evaluated, however bacteria are only detected at levels higher than 10 CFUs/g. Enumeration can be performed in certain cases where the specification is < 100 CFUs/g of Listeria monocytogenes.



  1. Three different types of swabs

We also now have three different swabs available for the equipment and environmental swabs for Listeria monocytogenes.