The key factor in the timely conclusion of this investigation was intersectoral collaboration among epidemiologists, microbiologists, veterinarians, statisticians and health and food safety authorities at national, regional and local levels.

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We report the findings of the study of 4185 food samples and 958 environmental samples collected in Italy in the period 1990-1999 and tested for the presence of Listeria monocytogenes. The strains isolated were biochemically and serologically characterised. We found a fairly high percentage of L. monocytogenes contamination in food (12.8%), whereas the level of contamination was lower in the environment (environment and work surfaces in food processing plants) (6.1%). Serotyping showed a prevalence of a few serotypes (i.e., 1/2a, 1/2b, 1/2c and 4b), which were the same as those found in clinical samples collected during outbreaks and from sporadic cases of listeriosis reported in Italy in the period considered. The geographical distribution of the strains of L. monocytogenes isolated from food samples is very similar to that of the clinical strains.

The risk of exposure toListeria monocytogenes(L. monocytogenes) when consuming Ready-to-Eat (RTE) seafood was assessed in the Veneto Region (Italy). Thirty-eight samples were analyzed, each sample consisted of three subunits belonging to the same batches. The first of the three units was examined immediately, the second was stored at +4°C (for all of its shelf-life) and the third at +10°C (for the latter third of itsshelf-life) before the analysis. Chemical-physical and microbiological parameters were tested simultaneously. Culture results showed the presence of viableL. monocytogenesin 9 (23,68%) of the 38 samples analysed, 3 (33,33%) of which with a concentration >100 cfu/g. PCR tests yielded 12L. monocytogenespositive samples. Semipreserves with aw (water activity) and pH values that favourL. monocytogenesgrowth were the only ones to result positive to microbiological and PCR tests. Temperature proved to be an important factor as it limits the growth ofL. monocytogenes, including products with potentially high competitive microbial charges. Four different serotypes were recovered and ribotyping has helped to highlight the genomic variability ofL. monocytogenesstrains in food. This supports the hypothesis thatL. monocytogenescontinues to evolve genetically to the detriment of phenotypic conservation.