Listeria monocytogenes in milk and dairy products

Listeria monocytogenes is ubiquitous bacteria. It causes listeriosis, a serious infectious disease which occurs as consequence of consumption of food contaminated with this pathogen bacterium. The frequency of incidence of listeriosis is low (1%), but with high mortality rate (30%). In certain countries (USA and Switzerland) large outbreaks of listeriosis were associated with consumption of fresh cheeses and milk. Studies on presence of L.monocytogenes in raw milk, carried out in Europe, have shown that 2,5-6% of samples can be contaminated with L.monocytogenes. In the process of production of milk and dairy products, it most commonly occurs as consequence of post-pasteurization contamination. L.monocytogenes has the ability to multiply and grow at low temperatures (40C) and to survive even on freezing temperatures, and as such poses risk for health of consumers, if found in milk, cheese, ice-cream and other dairy products. In order to prevent the contamination of product with this bacterium, producers much implement prevention measures, and special attention must be focused on critical points in the production process and adequate sanitation. The general characteristics of L.monocytogenes, are presented in the study, also its resistance to environment, some listeriosis outbreaks, its presence in milk and dairy products and major hygiene measures.