Attachment and biofilm formation by Escherichia coli O157:H7 at different temperatures, on various food-contact surfaces encountered in beef processing

Fscherichia coil 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 x 5 cm) were individually suspended into each of three substrates inoculated (6 log CFU/ml or g) with E. coli O157:H7 (rifampicin-resistant, six-strain composite) and then incubated (168 h) statically at 4 or 15 degrees C. The three tested soiling substrates included sterile cryptic 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 2.9 log 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 degrees C (168 h) by 2.2 to 5.4 log CFU/cm(2) and 1.0 to 2.8 log CFU/ml or g, respectively. At 4 degrees C (168 h), although pathogen levels decreased slightly in the substrates, numbers of adherent cells remained constant on coupons in ground beef (2.4 to 2.5 log CFU/cm(2)) and increased on coupons in TSB and fat-lean tissue homogenate by 0.9 to 1.0 and 1.7 to 2.0 log 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 degrees C), but also during cold storage (4 degrees C) temperatures, thus, rendering the design of more effective sanitation programs necessary. (C) 2011 Elsevier B.V. All rights reserved.