Inactivation of Escherichia coli O157:H7 on stainless steel upon exposure to Paenibacillus polymyxa biofilms |
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Authors: | Seonhwa Kim Jihyun Bang Hoikyung Kim Larry R Beuchat Jee-Hoon Ryu |
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Affiliation: | 1. Department of Food Bioscience and Technology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-701, Republic of Korea;2. Division of Human Environmental Sciences, Wonkwang University, Shinyong-dong, Iksan, Jeonbuk 570-749, Republic of Korea;3. Center for Food Safety Department of Food Science and Technology, University of Georgia, 1109 Experiment Street, Griffin, GA 30223-2797, USA |
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Abstract: | We investigated the potential use of biofilm formed by a competitive-exclusion (CE) microorganism to inactivate Escherichia coli O157:H7 on a stainless steel surface. Five microorganisms showing inhibitory activities against E. coli O157:H7 were isolated from vegetable seeds and sprouts. The microorganism with the greatest antimicrobial activity was identified as Paenibacillus polymyxa (strain T5). In tryptic soy broth (TSB), strain T5 reached a higher population at 25 °C than at 12 or 37 °C without losing inhibitory activity against E. coli O157:H7. When P. polymyxa (6 log CFU/mL) was co-cultured with E. coli O157:H7 (2, 3, 4, or 5 log CFU/mL) in TSB at 25 °C, the number of E. coli O157:H7 decreased significantly within 24 h. P. polymyxa formed a biofilm on stainless steel coupons (SSCs) in TSB at 25 °C within 24 h, and cells in biofilms, compared to attached cells without biofilm formation, showed significantly increased resistance to a dry environment (43% relative humidity RH]). With the exception of an inoculum of 4 log CFU/coupon at 100% RH, upon exposure to biofilm formed by P. polymyxa on SSCs, populations of E. coli O157:H7 (2, 4, or 6 log CFU/coupon) were significantly reduced within 48 h. Most notably, when E. coli O157:H7 at 2 log CFU/coupon was applied to SSCs on which P. polymyxa biofilm had formed, it was inactivated within 1 h, regardless of RH. These results will be useful when developing strategies using biofilms produced by competitive exclusion microorganisms to inactivate foodborne pathogens in food processing environments. |
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Keywords: | Competitive-exclusion Biofilm Paenibacillus polymyxa Escherichia coli O157:H7 Stainless steel surface |
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