Recent outbreak investigations revealed that recontamination after a listerial treatment is applied is the primary source of L. monocytogenes has been isolated from 8 to 44% of samples obtained from grain fields, pastures, mud, animal feces, wildlife feeding grounds, and related sources and can survive in moist soils for more than 295 days ( 22). Listeria monocytogenes is distributed widely in the environment, being able to survive and grow in soil and aqueous environments ( 15, 21). monocytogenes in biofilms at environmental temperatures of 4 to 37☌. These two bacterial isolates appear to be excellent competitive-exclusion candidates to control L.
monocytogenes (growth inhibition of >5 log 10 CFU of L.
lactis strain C-1-92) were highly inhibitory to L. monocytogenes on stainless steel coupons at 37, 15, 8, and 4☌. monocytogenes activity of these isolates was evaluated in biofilms of L. lactis (two isolates), and Lactobacillus plantarum (one isolate). The inhibitory isolates were identified as Enterococcus durans (six isolates), Lactococcus lactis subsp. monocytogenes growth (4 to 5 log CFU/ml) was observed for nine bacterial isolates at 37☌, two at 15 and 8☌, and three at 4☌. monocytogenes/ml and 10 5 CFU of the candidate competitive-exclusion microorganism/ml was combined in TSB-YE and incubated at 37☌ for 24 h, 15☌ for 14 days, 8☌ for 21 days, and 4☌ for 28 days. monocytogenes were assayed for antilisterial activity in coinoculated broth cultures containing tryptic soy broth with yeast extract (TSB-YE). All 24 isolates which produced metabolites inhibitory to L. Twenty-one of 257 bacterial isolates and 3 of 156 yeast isolates had antilisterial activity. A total of 413 microbial isolates were obtained from 12 drain biofilm samples and were assayed at 15 and 37☌ for activities that were bactericidal or inhibitory to L. Biofilms from drains in food processing facilities with a recent history of no detectable Listeria monocytogenes in floor drains were cultured for microorganisms producing antilisterial metabolites.
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