Listeriosis: The Dark Side of Refrigeration and Ensiling

Abstract

In contrast to most pathogenic bacteria, Listeria monocytogenes is psychrotrophic, capable of multiplying at low temperatures. In an era when food production and food storage heavily rely on refrigeration, this ability to grow (albeit slowly) in a cold environment has opened a new ecological niche for L. monocytogenes. Because of the severity of certain clinical manifestations (infections of the central nervous system, septicemia, and abortion), the high case-fatality rate (up to 30 % of cases), and the long incubation time, human listeriosis is now a zoonosis of major public health concern. L. monocytogenes causes invasive illness mainly in certain well-defined high-risk groups, including immunocompromised persons, pregnant women, neonates, and the elderly. However, listeriosis can occur in otherwise healthy individuals, particularly during an outbreak. The evolvement of silage as a dominant feed for ruminants constitutes another key factor, responsible for the emergence of listeriosis as a relevant animal disease. L. monocytogenes has been isolated from numerous species of mammals, birds, fish, crustaceans, and insects. Nevertheless, the primary habitats of L. monocytogenes are considered to be the soil and decaying vegetable matter, in which it survives and grows saprophytically.