Catherine Simpson Beauchamp

Colorado State University, Fort Collins, CO, United States

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Publications (4)8.19 Total impact

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    ABSTRACT: Studies examined the effects of meat-contact material types, inoculation substrate, presence of air at the liquid-solid surface interface during incubation, and incubation substrate on the attachment/transfer and subsequent biofilm formation by Escherichia coli O157:H7 on beef carcass fabrication surface materials. Materials studied as 2 × 5 cm coupons included stainless steel, acetal, polypropylene, and high-density polyethylene. A 6-strain rifampicin-resistant E. coli O157:H7 composite was used to inoculate (6 log CFU/mL, g, or cm²) tryptic soy broth (TSB), beef fat/lean tissue homogenate (FLH), conveyor belt-runoff fluids, ground beef, or beef fat. Coupons of each material were submerged (4 °C, 30 min) in the inoculated fluids or ground beef, or placed between 2 pieces of inoculated beef fat with pressure (20 kg) applied. Attachment/transfer of the pathogen was surface material and substrate dependent, although beef fat appeared to negate differences among surface materials. Beef fat was the most effective (P < 0.05) inoculation substrate, followed by ground beef, FLH, and TSB. Incubation (15 °C, 16 d) of beef fat-inoculated coupons in a beef fat homogenate (pH 4.21) allowed the pathogen to survive and grow on coupon surfaces, with maximal biofilm formation observed between 2 and 8 d of storage and when air was present at the liquid-solid interface. The results indicated that the process of fabricating beef carcasses may be conducive to the attachment of E. coli O157:H7 onto meat-contact surfaces and subsequent biofilm formation. Furthermore, it is recommended that substrates found in beef fabrication settings, rather than laboratory culture media, be used in studies designed to investigate E. coli O157:H7 biofilm development and control in these environments. PRACTICAL APPLICATION: Findings of this study provide knowledge on the effect of type of beef carcass fabrication surface material, fabrication-floor fluids and residues, and incubation conditions on attachment/transfer and subsequent biofilm formation by E. coli O157:H7. The results highlight the importance of thoroughly cleaning soiled surfaces to remove all remnants of beef fat or other organic material that may harbor or protect microbial contaminants during otherwise lethal antimicrobial interventions.
    Journal of Food Science 05/2012; 77(6):M343-7. · 1.78 Impact Factor
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    ABSTRACT: This study evaluated the efficacy of various sanitizers against Escherichia coli O157:H7 cells in biofilms formed on surface materials used in beef fabrication facilities. Coupons (2 × 5 cm) of stainless steel, acetal, and high-density polyethylene were inoculated (3–4 log CFU/cm2) with rifampicin-resistant E. coli O157:H7 (6-strain mixture) and incubated at 15°C in an unsterilized beef fat-lean tissue homogenate (pH 5.66). After 3 days of incubation, attached cells were challenged (for 1 or 10 min) by submerging coupons in minimum and maximum recommended concentrations of each of seven sanitizing solutions or distilled water (control). Sanitizer treatments reduced E. coli O157:H7 on coupons by 0.0 to 2.2 log CFU/cm2, and treatment efficacy decreased in the order acidified sodium chlorite > peroxyacetic acid > potassium peroxymonosulfate/sodium chloride = peroxyacetic acid/octanoic acid mixture (PA/OA) > cetylpyridinium chloride > quaternary ammonium chloride compound mixture (QACC) = sodium hypochlorite (SH) = water control. Pathogen reductions generally increased as sanitizer concentration and exposure time increased. The influence of biofilm age (0, 3 and 7 days incubation at 15°C) on sanitizer (SH, QACC and PA/OA) efficacy was evaluated in a separate experiment; results showed that E. coli O157:H7 biofilm cells became less sensitive to most sanitizer treatments as biofilm age increased. Surface material did not (P ≥ 0.05) influence the fate of biofilm cells during sanitizing treatments. While no sanitizer consistently reduced pathogen populations by more than 2.2 log cycles on soiled surfaces, approved concentrations of acidified sodium chlorite and peroxyacetic acid-based sanitizers may be more effective than other sanitizers against E. coli O157:H7 on inadequately cleaned surfaces.
    Food Protection Trends. 01/2012; 32(4):173-182.
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    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.
    International journal of food microbiology 10/2011; 149(3):262-8. · 3.01 Impact Factor
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    ABSTRACT: Little information is available regarding the fate of Listeria monocytogenes during freezing, thawing and home storage of frankfurters even though recent surveys show that consumers regularly store unopened packages in home freezers. This study examined the effects of antimicrobials, refrigerated storage, freezing, thawing method, and post-thawing storage (7 degrees C) on L. monocytogenes on frankfurters. Inoculated (2.1 log CFU/cm(2)) frankfurters formulated without (control) or with antimicrobials (1.5% potassium lactate plus 0.1% sodium diacetate) were vacuum-packaged, stored at 4 degrees C for 6 or 30 d and then frozen (-15 degrees C) for 10, 30, or 50 d. Packages were thawed under refrigeration (7 degrees C, 24 h), on a countertop (23 +/- 2 degrees C, 8 h), or in a microwave oven (2450 MHz, 1100 watts, 220 s followed by 120 s holding), and then stored aerobically (7 degrees C) for 14 d. Bacterial populations were enumerated on PALCAM agar and tryptic soy agar plus 0.6% yeast extract. Antimicrobials completely inhibited (p < 0.05) growth of L. monocytogenes at 4 degrees C for 30 d under vacuum-packaged conditions, and during post-thawing aerobic storage at 7 degrees C for 14 d. Different intervals between inoculation and freezing (6 or 30 d) resulted in different pathogen levels on control frankfurters (2.1 or 3.9 log CFU/cm(2), respectively), while freezing reduced counts by <1.0 log CFU/cm(2). Thawing treatments had little effect on L. monocytogenes populations (<0.5 log CFU/cm(2)), and post-thawing fate of L. monocytogenes was not influenced by freezing or by thawing method. Pathogen counts on control samples increased by 1.5 log CFU/cm(2) at d-7 of aerobic storage, and reached 5.6 log CFU/cm(2) at d-14. As indicated by these results, consumers should freeze frankfurters immediately after purchase, and discard frankfurters formulated without antimicrobials within 3 d of thawing and/or opening.
    Food Microbiology 02/2010; 27(1):144-9. · 3.41 Impact Factor