ABSTRACT
Listeria monocytogenes is a Gram-positive motile bacillus having a characteristic tumbling motility. It consists of 26 species. The genus has two major groups, Listeria sensu stricto consisting of Listeria monocytogenes and five other species and Listeria sensu lato consisting of the remainder 20 species. The organism is found widely in the environment from soil, water, vegetables and food (e.g. soft cheese) to many different animal groups including food-source animals (e.g. sheep and poultry), companion animals (e.g. dogs) and Zoo and wild animals (e.g. rats, fish, birds). It causes disease in both animals and humans and is a good example of a “One Health” approach to disease research and treatment. Risk factors for disease are immunosuppression and pregnancy. It causes similar disease in humans and animals including gastroenteritis, septicemia, meningitis, meningoencephalitis, fetal death and post-natal disease. Large outbreaks of food-related disease occur requiring extensive international epidemiologic investigations. The organism after penetrating cells can escape the phagosome and pass from cell to cell without exposing itself to the immune system. Diagnosis is mainly by cultural techniques and treatment is with a beta-lactam, aminoglycoside or cotrimoxazole. A vaccine does not currently exist.
