title: Characterization of interactions between Escherichia coli O157:H7 with epiphytic bacteria in vitro and on spinach leaf surfaces.
abstract: This study characterized the types of interactions between Escherichia coli O157:H7 and spinach phylloepiphytic bacteria and identified those that influence persistence of E. coli O157:H7 on edible plants. A total of 1512 phylloepiphytic bacterial isolates were screened for their ability to inhibit or to enhance the growth of E. coli O157:H7 in vitro and on spinach leaf surfaces. Fifteen different genera, the majority belonging to Firmicutes and Enterobacteriaceae, reduced growth rates of E. coli O157:H7 in vitro by either nutrient competition or acid production. Reduced numbers of E. coli O157:H7 were recovered from detached spinach leaves that were co-inoculated with epiphytic isolates belonging to five genera. A 1.8 log reduction in E. coli O157:H7 was achieved when co-inoculated with Erwinina perscinia and 20% cellobiose, a carbon source used by the phylloepiphytes but not E. coli O157:H7. The reduction on leaves was significantly less than reduction measured in vitro. Phylloepiphytic bacteria belonging to eight different genera, increased numbers of E. coli O157:H7 when co-cultured in vitro on spent medium and when co-cultured on detached spinach leaves. The results, showing reduction of E. coli O157:H7 numbers by natural epiphytic bacteria, support the hypothesis that native plant microbiota can be used for bio-control of foodborne pathogens, however, other epiphytes may promote the persistence of enteric pathogens on the phyllosphere.
authors.affiliation: Department of Food Science and Technology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Lopez-Velasco
authors.forename: Heather A
authors.initials: HA
authors.lastname: Tydings
authors.forename: Renee R
authors.initials: RR
authors.lastname: Boyer
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Falkinham
authors.forename: Monica A
authors.initials: MA
authors.lastname: Ponder
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D061046:Biological Control Agents; D015169:Colony Count, Microbial; D004926:Escherichia coli; D019453:Escherichia coli O157 / Q000254:growth & development* / Q000302:isolation & purification; D005506:Food Contamination; D005516:Food Microbiology; D018515:Plant Leaves / Q000382:microbiology; D018724:Spinacia oleracea / Q000382:microbiology*
chemical_list: D061046:Biological Control Agents