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Title: Isolation of biofilm-forming bacteria from a fresh-cut processing plant and co-culturing with E. coli O157:H7

Author
item LIU, TONG - University Of Maryland
item Lefcourt, Alan
item Nou, Xiangwu
item Shelton, Daniel
item LO, Y - University Of Maryland

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 2/10/2011
Publication Date: 6/11/2011
Citation: Liu, T., Lefcourt, A.M., Nou, X., Shelton, D.R., Lo, Y. 2011. Isolation of biofilm-forming bacteria from a fresh-cut processing plant and co-culturing with E. coli O157:H7. Annual Meeting of the Institute of Food Technologists.

Interpretive Summary:

Technical Abstract: In produce processing plants, biofilms can theoretically provide a supporting environment for pathogenic bacteria that is resistant to cleaning and sanitizing efforts. The objective of this study was to recover bacteria from a commercial produce processing plant that have the ability to form biofilms, and then to determine if these organisms could sustain the growth of E. coli O157:H7 in binary culture biofilms. Swab samples were collected from cutting boards, cutting/peeling tools, conveyor belts, surfaces of pre-cut produce, and floors. The biofilm-forming capacity of isotropic isolated strains from non-selective media (TSA, MAC) was evaluated using standard micro-titer plate methods (described below). Seven of the 103 random isolates tested showed biofilm producing ability in dilute TSB; one isolate was from a cutting board, one from a brush in a peeler, and the remainders were isolated from cantaloupe juice collected from cutting surfaces during processing using an eye-dropper. The isolates, all with strong biofilm formation potential, were mixed with a single E. coli O157:H7 strain. The E. coli strain, by itself, is a weak biofilm former. Different concentrations of isolates and E. coli’s suspensions were mixed together and inoculated in 96-well micro-titer plates. After 24h, the plates were washed and crystal violet added, then the plates were washed and acetic acid added, finally the plates were shaken for 5 min. Biomass was measured as optical density at 600 nm. Comparisons of co-culture and mono-culture results, controlling for mono-culture dilutions of biofilm formers, showed a relative increase in biomass for the co-culture for at least one inoculum ratio of E. coli to biofilm former. These results suggested that biofilms formed by bacteria recovered from a natural processing plant environment have the potential to provide a microenvironment for E. coli O157:H7 to survive washing and sanitation efforts