Listeria monocytogenes

Test code: B0044 - Ultrasensitive qualitative detection of Listeria monocytogenes bacteria by real time polymerase chain reaction. Assay does not detect other Listeria species.

Bacteria of the genus Listeria are widely distributed in the environment and are a common contaminant of food. Listeria monocytogenes is of particular concern, as it is the major culprit of listeriosis. Food products most frequently associated with listeriosis are soft cheeses, particularly those made from unpasteurized milk, and ready-to-eat animal and human food products containing meat.

Infection with L. monocytogenes can result in septicemia, meningoencephalitis and abortion in humans and animals, primarily affecting pregnant, newborn and immunocompromised individuals.

L. monocytogenes is a non-sporogenic, facultative intracellular gram-positive bacterium that has the ability to survive high and low temperatures, low pH and high salinity. It is not acid-resistant and can be grown on a tryptose and blood agar.

Traditionally, culture-based identification of Listeria from food, fecal or environmental samples relied on selective enrichments and subsequent biochemical analyses. This analytical approach is laborious and time-consuming (Almeida and Almeida, 2000), and is prone to contamination during handling and incubation.

Detection of this pathogen by polymerase chain reaction is highly sensitive and specific. The assay is performed more quickly than culture, on a wide range of specimen types, with a high degree of accuracy.

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of Listeriosis
• Safety monitoring of food products and processing facilities
• Minimize human and animal exposure to L. monocytogenes

References:
Almeida, P.F., Almeida, R.C.C. 2000: A PCR protocol using inl gene as a target for specific detection of Listeria monocytogenes. Food Control II: 97-101

Specimen requirement: Food swab, or environmental surface swab, or rectal swab, or 0.5 ml feces, shipped overnight at room temperature.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected