Following the initial isolation and description in 1926, L. monocytogenes is of worldwide prevalence and is associated with serious disease in various animals, including humans. Our knowledge of this bacterial pathogen and the various forms of listeriosis that it causes has, until recently, been minimal. Still, recent advances in taxonomy, isolation methods, bacterial typing, molecular biology, and cell biology have extended our knowledge. It is an exquisitely adaptable environmental bacterium capable of existing as an animal pathogen and plant saprophyte with a powerful array of regulated virulence factors.
Most cases of listeriosis arise from ingesting contaminated food; in the UK, the disease is prevalent in ruminants fed on silage. Although several forms of listeriosis are easily recognized, such as encephalitis, abortion, and septicemia, the epidemiological aspects and pathogenesis of infection in ruminants remain poorly understood. The invasion of peripheral nerve cells and rapid entry into the brain is postulated as a unique characteristic of its virulence. However, relevant and practical disease models are still required to investigate this phenomenon.
