Inhibitory effects of Enterococcus strains obtained from a probiotic product on in vitro growth of Salmonella enterica serovar enteritidis strain IFO3313.

Enterococcus faecium and Enterococcus gallinarum strains were isolated from a commercial probiotic product and the effects of these strains on the growth of Salmonella enterica serovar Enteritidis strain IFO3313 were investigated. Viable cell counts of Salmonella Enteritidis in mixed cultures with the probiotic product isolate of E. faecium were significantly (P < 0.05) lower than those in pure cultures after 6, 8, and 24 h when the cultures were incubated in heart infusion broth at 37 and 41 degrees C. Significant differences in viable cell counts of Salmonella Enteritidis in mixed cultures with the probiotic product isolate of E. gallinarum and those in pure cultures were also observed after 8 and 24 h at 37 and 41degrees C. Similar observations were shown in mixed cultures of Salmonella Enteritidis with the reference strains of E. faecium GIFU8355 and E. gallinarum ATCC 49573. Significant differences in viable cell counts of these enterococcal strains were not shown among pure and mixed cultures with Salmonella Enteritidis. The pH values in pure and mixed cultures were 7.0 or 7.5 throughout the experiments. E. faecium strains were found to harbor the genes encoding enterocins A and B and showed inhibitory zones with a diameter of 4 to 6 mm against growth of Salmonella Enteritidis in the enterocin production assays. However, the E. gallinarum strains possessed neither of the enterocin genes tested and exhibited no inhibition zone in the enterocin production assays. These results indicated that enterococcal strains exhibit inhibitory effects on the growth of Salmonella Enteritidis and these effects were due to both enterocin and nonenterocin factors.