Competitive inhibition of Listeria monocytogenes by lactic acid bacteria isolated from food processing facilities
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Enterococcus faecium, Lactococcus lactis subsp. lactis, Lactobacillus pentosus, and Lactococcus lactis, isolated from food processing facilites, were exceptionally inhibitory to the growth of L. monocytogenes in modified tryptic soy broth (mTSB) at 37, 15, 8, or 4 oC. Among these, E. faecium was most inhibitory. When combined in mTSB, E. faecium (initially at 10 6 cfu/ml) suppressed the growth of L. monocytogenes (initially at 10 3 cfu/ml) by 6.5 log10cfu/ml at 24 h at 37 oC, by 6 log10cfu/ml at 7 d at 15 oC, by 5 log10cfu/ml at 21 days at 8 oC, and by 3.5 to 4 log10cfu/ml at 28 d at 4 oC. With a higher inoculum of E. faecium (10 7 cfu/ml), L. monocytogenes (10 3 cfu/ml) was not detectable after incubation at 15 o C for 24 h and after 7 days of incubation at 8 oC. Competitive exclusion bacteria are potential alternative hurdles to controlling L. monocytogenes in food processing facilities.