Three strains of lactic acid bacteria (LAB) and a commercial probiotic were selected to evaluate their in vitro activity towards Listeria monocytogenes. The strains Lactococcus lactis ssp. lactis, strain 340, L. lactis ssp. lactis, strain 16; Lactobacillus casei ssp. casei, strain 208 and Enterococcus faecium UBEF-41 were inoculated into skim milk and brain heart infusion broth (BHI) to get an initial Lactococcus: Lactobacillus: E. faecium UBEF-41 ratio of 2:1:1 and a concentration of approximately 7 log cfu mL À1 until challenge vs. pathogen. L. monocytogenes ATCC 7644 was also inoculated in same media to get approximately 4 log cfu mL À1 . Growth curves in skim milk and BHI at 4, 10 and 30 C, respectively were studied for: (i) LAB formulation; (ii) L. monocytogenes and (iii) LAB vs. L. monocytogenes. When challenged with LAB, at 30 C in milk, L. monocytogenes was not detectable after day-3 and in BHI it decreased below log cfu mL À1 after day-5. At 10 and 4 C, in both media, L. monocytogenes counts were always significantly lower (p < .001) than the counts of L. monocytogenes alone from day-2 for milk at 4 C and BHI at 10 C and from day-7 for BHI at 4C and milk at 10 C. In conclusion, the proposed formulation was able to limit L. monocytogenes in vitro growth, even at refrigeration temperature.
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