title: Inhibition of Escherichia coli O157:H7 and Salmonella enterica on spinach and identification of antimicrobial substances produced by a commercial Lactic Acid Bacteria food safety intervention.
abstract: The microbiological safety of fresh produce is of concern for the U.S. food supply. Members of the Lactic Acid Bacteria (LAB) have been reported to antagonize pathogens by competing for nutrients and by secretion of substances with antimicrobial activity, including organic acids, peroxides, and antimicrobial polypeptides. The objectives of this research were to: (i) determine the capacity of a commercial LAB food antimicrobial to inhibit Escherichia coli O157:H7 and Salmonella enterica on spinach leaf surfaces, and (ii) identify antimicrobial substances produced in vitro by the LAB comprising the food antimicrobial. Pathogens were inoculated on freshly harvested spinach, followed by application of the LAB antimicrobial. Treated spinach was aerobically incubated up to 12 days at 7 °C and surviving pathogens enumerated via selective/differential plating. l-Lactic acid and a bacteriocin-like inhibitory substance (BLIS) were detected and quantified from cell-free fermentates obtained from LAB-inoculated liquid microbiological medium. Application of 8.0 log10 CFU/g LAB produced significant (p < 0.05) reductions in E. coli O157:H7 and Salmonella populations on spinach of 1.6 and 1.9 log10 CFU/g, respectively. It was concluded the LAB antimicrobial inhibited foodborne pathogens on spinach during refrigerated storage, likely the result of the production of metabolites with antimicrobial activity.
authors.affiliation: Department of Animal Science, Texas A&M University, College Station, TX 77843-2471, United States. Electronic address: tcalix@gmail.com.
authors.forename: Thelma F
authors.initials: TF
authors.lastname: Cálix-Lara
authors.forename: Mahitha
authors.initials: M
authors.lastname: Rajendran
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Talcott
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Smith
authors.forename: Rhonda K
authors.initials: RK
authors.lastname: Miller
authors.forename: Alejandro
authors.initials: A
authors.lastname: Castillo
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Sturino
authors.forename: T Matthew
authors.initials: TM
authors.lastname: Taylor
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001430:Bacteriocins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D005519:Food Preservation; D059022:Food Safety; D007777:Lactobacillaceae / Q000737:chemistry* / Q000378:metabolism; D019779:Salmonella enterica / Q000187:drug effects* / Q000254:growth & development; D018724:Spinacia oleracea / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins
keywords: Antimicrobials; Biopreservation; Escherichia coli O157:H7; Lactic Acid Bacteria; Salmonella; Spinach