Caratterizzazione genotipica e sierologica di Listeria monocytogenes isolata da alimenti e ambienti di lavorazione

Fifty-one strains of Listena nxonocytogenes previously isolated from foods and food environments were serotyped and three new multiplex PCRs were used to detect the maln virulence genes. These results were analyzed statistically in order to understand if correlations exist between the presence of virulence genes, serotype and food. The majority ofthe strains belonging to serotype 1/2a and all the strains belonging to serotype 4b were isolated from fish or fish environment. On the contrary, the majorify of the strains belonging to serotype 1/2b and all the strains belonging to serotype 1/2c were isolated from meat and meat environment. All tested stains showed the presence of all virulence genes, suggesting that all the strains could be virulent. The actA gene showed a polymorphism that could be related to a different level of strain pathogenicity, but this aspect should be furtber investigated by in vivo or in vitro tests. Statistical analysis showed a correlation between food matrix, serotype and one of the two forms of actA gene. In particular, fish matrix was related to the form of actA gene of 268 bp and to the serotype 4b, frequently isolated from cases of human illness.