Freq. a The following loci: invA, safC, bcfC, fimA and ssaQ were present in all the strains; the genes gipA, gogB, sspH2, sodC1, gtgE, spvC, stfE, ipfD and pefA were not found in any of these strains. [19, 20] . The data presented here suggest that agfA might increase bacterial pathogenicity. Nevertheless, we cannot reject the hypothesis that the mouse model chosen for in vivo experiments could have influenced the virulence phenotype of the tested strains originally isolated from water buffalo calves. Therefore, future studies will be necessary to exclude the possibility that the phenotypic differences observed among the tested Salmonellae are dependent on the animal model or on other virulence factors not included in this study. However, in vivo experiments carried out in mouse models represent a good preliminary source of information on the expression of traits associated with pathogenicity of Salmonella in mammalian species.