title: Attachment and biofilm formation by Escherichia coli O157:H7 at different temperatures, on various food-contact surfaces encountered in beef processing.
abstract: Escherichia coli O157:H7 attached to beef-contact surfaces found in beef fabrication facilities may serve as a source of cross-contamination. This study evaluated E. coli O157:H7 attachment, survival and growth on food-contact surfaces under simulated beef processing conditions. Stainless steel and high-density polyethylene surfaces (2×5cm) were individually suspended into each of three substrates inoculated (6log CFU/ml or g) with E. coli O157:H7 (rifampicin-resistant, six-strain composite) and then incubated (168h) statically at 4 or 15°C. The three tested soiling substrates included sterile tryptic soy broth (TSB), unsterilized beef fat-lean tissue (1:1 [wt/wt]) homogenate (10% [wt/wt] with sterile distilled water) and unsterilized ground beef. Initial adherence/attachment of E. coli O157:H7 (0.9 to 2.9log CFU/cm(2)) on stainless steel and high-density polyethylene was not affected by the type of food-contact surface but was greater (p<0.05) through ground beef. Adherent and suspended E. coli O157:H7 counts increased during storage at 15°C (168h) by 2.2 to 5.4log CFU/cm(2) and 1.0 to 2.8log CFU/ml or g, respectively. At 4°C (168h), although pathogen levels decreased slightly in the substrates, numbers of adherent cells remained constant on coupons in ground beef (2.4 to 2.5log CFU/cm(2)) and increased on coupons in TSB and fat-lean tissue homogenate by 0.9 to 1.0and 1.7 to 2.0log CFU/cm(2), respectively, suggesting further cell attachment. The results of this study indicate that E. coli O157:H7 attachment to beef-contact surfaces was influenced by the type of soiling substrate and temperature. Notably, attachment occurred not only at a temperature representative of beef fabrication areas during non-production hours (15°C), but also during cold storage (4°C) temperatures, thus, rendering the design of more effective sanitation programs necessary.
authors.affiliation: Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, 1171 Campus Delivery, Fort Collins, CO 80523, USA.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Dourou
authors.forename: Catherine Simpson
authors.initials: CS
authors.lastname: Beauchamp
authors.forename: Yohan
authors.initials: Y
authors.lastname: Yoon
authors.forename: Ifigenia
authors.initials: I
authors.lastname: Geornaras
authors.forename: Keith E
authors.initials: KE
authors.lastname: Belk
authors.forename: Gary C
authors.initials: GC
authors.lastname: Smith
authors.forename: George-John E
authors.initials: GJ
authors.lastname: Nychas
authors.forename: John N
authors.initials: JN
authors.lastname: Sofos
mesh_terms: D000818:Animals; D018441:Biofilms / Q000254:growth & development*; D002417:Cattle; D015169:Colony Count, Microbial; D004926:Escherichia coli; D019453:Escherichia coli O157 / Q000254:growth & development / Q000502:physiology*; D005511:Food Handling; D008460:Meat / Q000382:microbiology*; D020959:Polyethylene; D013193:Stainless Steel; D013696:Temperature; D014867:Water
chemical_list: D014867:Water; D013193:Stainless Steel; D020959:Polyethylene