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United States Department of Agriculture

Agricultural Research Service


Location: Environmental Microbial & Food Safety Laboratory

Title: Gram-negative phytopathogenic and soil bacteria enhance the presence of Escherichia coli O157:H7 in dual-species biofilms)

item Liu, Nancy
item Nou, Xiangwu
item Lo, Y. Martin

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/9/2012
Publication Date: 6/25/2012
Citation: Liu, N., Nou, X., Lo, Y. 2012. Gram-negative phytopathogenic and soil bacteria enhance the presence of Escherichia coli O157:H7 in dual-species biofilms. [abstract].

Interpretive Summary:

Technical Abstract: Biofilms formed by native microflora may provide a pathway for human bacterial pathogens to survive and cause cross-contamination in centralized fresh-cut processing manufactures, consequently leading to severe foodborne outbreaks. The objective of this study is to determine the influence of individual bacteria strains isolated from native microflora in two local fresh-cut processing plants on the survival of laboratory E. coli O157:H7 strain in dual-species biofilms. Fourteen strains isolated from food contact and non-food contact surfaces in two local fresh-cut processing facilities, including 5 phytobacterial strains, 4 phytopathogenic bacterial strains and 5 plant associated soil bacterial strains, were employed to form biofilms with E. coli O157:H7 strains. The total biomass of dual-species biofilms formed by individual bacteria isolate and E. coli O157:H7 were compared with that of the monocultural biofilm of both strains in the combination, respectively. It was found that phytobacteria commonly found on fresh produce, such as Pseudomonas fluorescens and Rhanella aquatilis, did not significantly affect on E. coli O157:H7 survival in the dual-species biofilms. Contrarily, certain Gram-negative phytopathogenic bacteria, such as Burkholderia caryophylli and Rhizobium radiobacter, enhanced E. coli O157:H7 presence in dual-species biofilms. All five tested plant-associated soil bacteria, namely, Acinetobacter spp., Flavimonas oryzihabitans, Flavobacterium resinovorum, Ralstonia insidiosa and Sphingomonas rhizophila, were able to promote the presence of E. coli O157:H7 with a total increase of 1-2 log CFU/cm2. A wide taxonomical spectrum of native bacterial strains, including Alpha, Beta, Gamma Proteobacteria and Flavobacteria, exhibited the potential to enhance the presence of E. coli O157:H7 through dual-species biofilm formation. The ability of Gram-negative bacteria in fresh-cut processing environment to assist in the survival of E. coli O157:H7 in dual-species boifilms ushers the development of novel intervention strategies to minimize produce-harbored foodborne illness.

Last Modified: 05/23/2017
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