Listeria is a genus of Gram-positive, non-sporeforming, rod-shaped bacteria. Of the known species of the genus Listeria, Listeria monocytogenes deserves particular mention as a human and animal pathogen; L. ivanovii is mainly pathogenic in animals, while the remaining species are considered harmless environmental bacteria. They are characterized by several factors, including their ability to grow at refrigeration temperatures (2–8°C), causing contamination of ready-to eat foods to pose a serious risk.
Consequently, food legislation in many countries specifies strict limits for Listeria spp. or Listeria monocytogenes. In the conduct of risk-related quality controls in food, tests should be run for L. monocytogenes, and for the Listeria Genus in general.
The presence of Listeria – in particular of L. innocua – is an indicator for critical hygienic conditions in the production process. A drastic increase in the incidence of food infection caused by Listeria has resulted in a demand for reliable and rapid methods of detection. Apart from traditional culture methods, immunological techniques are becoming ever more popular with users due to their superior specificity and sensitivity.
Listeria monocytogenes is one of the most widely distributed foodborne pathogens in the world and is responsible for severe infections in immunocompromised persons, pregnant women and neonates. As a result, the mortality rate in infected individuals is high despite the relatively low number of cases around the world.
Listeria infections (listeriosis) can result in anything from mild gastroenteritis to severe cases of sepsis, meningitis, encephalitis or abortion. Due to the ubiquitous distribution of Listeria and their capability to grow at refrigeration temperatures (2–8°C), food products constitute one of the main sources of infection.