Listeria monocytogenes strains, isolated from various sources (food, environment, and animals), were used to test different
PCR-based methods to investigate their capability to define the strain origin. RAPD-PCR with three primers and the SAU-PCR
method, in which the DNAwas first digested with the Sau3A restriction endonuclease and then amplified with a primer designed
on the restriction site, were carried out, and the profiles obtained were used to perform cluster analysis. Based on the cluster
analysis of Listeria spp. strains, obtained from international collections, the coefficient of similarity was selected. The results
obtained showed that the methods tested in the study gave different levels of differentiation between the strains tested. The RAPD
protocol using the P1254 primer and the SAU-PCR gave appreciable results only for strains isolated from animals and from a food
processing plant in two different periods of the year 2003. Better differentiation was observed using the RAPD-PCR with primer
D8635. As a matter of fact, it was able to distinguish L. monocytogenes obtained from different species of animals, different food
samples and strains from the same production plant isolated in different periods of the year. Also primer M13 gave positive results,
but the coefficient of similarity to use had to be increased to 80%. On the basis of the results observed, RAPD-PCR with primers
D8635 and M13 should be considered reliable tools for epidemiological investigations focusing on L. monocytogenes
