Pathogenic organisms in milk and milk products: the situation in France and in Europe

Milk and dairy products harbour a natural microbial flora and/or other micro-organisms, which vary within the wide range of products available on the French market. The origin of contamination by pathogenic bacteria varies with the type of product and the mode of production and processing. Contamination of milk and dairy products by pathogenic micro-organisms can be of endogenous origin, following excretion from the udder of an infected animal. Contamination may also be of exogenous origin, through direct contact with infected herds or through the environment (e.g. water, personnel). Treatment and processing of milk can inhibit or encourage the multiplication of micro-organisms. The authors describe the relevant aspects of bacterial physiology and ecology, the occurrence of bacteria in dairy products, and the public health significance for each of the principal micro-organisms found in such products. Bacteria most frequently involved are mycobacteria, Brucella sp., Listeria monocytogenes, Staphylococcus aureus and enterobacteria (including toxigenic Escherichia coli and Salmonella). At present, systems of testing and surveillance are required for the control of pathogenic bacteria in milk and dairy products, as specified by regulations currently being developed for all countries in the European Union. Preventive measures should take into account the well-established facts concerning the potential microbiological impact of pathogenic bacteria on milk and dairy products. There should be increased recourse to risk analysis methods to assess the threat to the consumer with regard to the presence of pathogenic bacteria in food.