[Spreading of Listeria monocytogenes in cheese dairy products]

The increasingly more frequent occurrences of epidemic nidus of Listeria monocytogenes induced the E.E.C. Health Organisation to research into the diffusion of such microorganism. During the first six months of 1988 the "Istituto Superiore di Sanità" began a research into the presence of Listeria monocytogenes in milk and dairy products. The biological section of the "Laboratorio di Sanità Pubblica" of Grugliasco (Torino) participated in this study and in this work methods and results are reported. Changing the F.D.A. methods, incubation time was reduced. The percentage of positive samples was 4.6%, especially in dairy products with cheese mould. These results confirm an environmental diffusion of Listeria monocytogenes, nevertheless non illness caused by Listeria monocytogenes was recorded in the population who ate these products. Therefore the problem of Listeria monocytogenes pathogenicity and its diffusion by food remains to be clarified.