title: An in vitro model to study interactions between Escherichia coli and lactic acid bacterial inoculants for silage in rumen fluid.
abstract: Previous studies have shown that silages treated with lactic acid bacteria (LAB) inoculants enhance ruminants' performance. The objective of the current experiments was to develop an in vitro model to study interactions between LAB silage inoculants and inoculated silages and Escherichia coli (EC) in rumen fluid (RF). Our hypothesis was that some inoculants inhibit EC in RF. For that purpose buffered RF was incubated under anaerobic conditions at 39°C with commercial strains of LAB silage inoculants or with laboratory corn and wheat silages treated with these LAB, an EC strain and with various ruminant feed ingredients. The EC strain was originally isolated from cattle manure and tagged with a plasmid expressing the green fluorescence protein and kanamycin and streptomycin resistance. Results indicate that the LAB or the treated silages did not suppress EC numbers in the RF. When the pH of the RF decreased below 5·0 the EC disappeared. We conclude that both LAB inoculants for silage and EC survived in RF for several days; however, the inoculants and silages treated with such inoculants did not inhibit EC in RF in vitro.
  
  
  CONCLUSIONS
  Forage crops, silage and hay are initial stages of the food chain for humans. Cattle harbours and sheds enterobacteria regularly, some strains of which are pathogens. These can contaminate forage crops through field fertilization with cattle manure. The objective of this study was to develop an in vitro model to test whether lactic acid bacteria, which are used in silage inoculants, alone or in treated silages can inhibit Escherichia coli in rumen fluid. This study presents safety aspects and it is also part of a broad research effort aimed at finding out how LAB silage inoculants and inoculated silages enhance ruminant performance or exert probiotic effects in ruminants.
authors.affiliation: Department of Food Quality and Safety, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
authors.forename: Z G
authors.initials: ZG
authors.lastname: Weinberg
authors.affiliation: Department of Food Quality and Safety, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Food Quality and Safety, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
authors.forename: V
authors.initials: V
authors.lastname: Volchinski
authors.affiliation: Department of Food Quality and Safety, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
authors.forename: S
authors.initials: S
authors.lastname: Sela
authors.affiliation: Department of Animal Science, University of Florida, Gainesville, FL, USA.
authors.forename: I M
authors.initials: IM
authors.lastname: Ogunade
authors.affiliation: Department of Animal Science, University of Florida, Gainesville, FL, USA.
authors.forename: A
authors.initials: A
authors.lastname: Adesogan
mesh_terms: D059827:Agricultural Inoculants; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D005285:Fermentation; D049452:Green Fluorescent Proteins / Q000235:genetics; D007612:Kanamycin / Q000494:pharmacology; D019344:Lactic Acid / Q000378:metabolism; D007778:Lactobacillus / Q000378:metabolism*; D019936:Probiotics; D012417:Rumen / Q000382:microbiology*; D012418:Ruminants; D012820:Silage / Q000382:microbiology*; D013307:Streptomycin / Q000494:pharmacology; D014908:Triticum / Q000382:microbiology*; D003313:Zea mays / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D049452:Green Fluorescent Proteins; D019344:Lactic Acid; D007612:Kanamycin; D013307:Streptomycin
keywords: Escherichia coli; fermentation; lactic acid bacteria; modelling; probiotics