P1-43 Evaluation of Beef Trim Sampling Methods for Detection of Shiga Toxin-producing Escherichia coli (STEC)

Monday, July 29, 2013
Exhibit Hall (Charlotte Convention Center)
Randall Phebus, Kansas State University, Manhattan, KS
John Luchansky, U.S. Department of Agriculture-ARS-ERRC, Wyndmoor, PA
Anna Porto-Fett, U.S. Department of Agriculture-ARS-ERRC, Wyndmoor, PA
Harshavardhan Thippareddi, University of Nebraska-Lincoln, Lincoln, NE
David Marx, University of Nebraska-Lincoln, Lincoln, NE
Rachael Sullivan, Kansas State University, Manhattan, KS
Susan Hettenbach, Kansas State University, Manhattan, KS
Casey Paddock, Kansas State University, Manhattan, KS
Nicholas Baumann, Kansas State University, Manhattan, KS
Nicholas Sevart, Kansas State University, Manhattan, KS
Minto Michael, Kansas State University, Manhattan, KS
Donka Milke, Kansas State University, Manhattan, KS
Nigel Harper, Kansas State University, Manhattan, KS
Carla Schwan, Kansas State University, Manhattan, KS
Andre Senecal, U.S. Army Natick RDE Center, Natick, MA
Manpreet Singh, Auburn University, Auburn, AL
Introduction: Presence of Shiga toxin-producing Escherichia coli (STEC) is a major concern in ground beef. The methods for sampling commercial beef trim prior to grinding currently includes excision and core sampling, with some variations noted (e.g., N-value and number of combo units making up a lot). 

Purpose: The purpose of this study was to determine the efficacy of five different sampling methods for detecting randomized STEC contamination in beef trim contained in single combo units. 

Methods: Standard combo bins (1.1 x 0.9 x 1.1 m) were divided into 27 sectors (9 on the bottom, middle and top layers each).  A STEC strain (O103, O145 or O157) was inoculated onto a 908 g piece of beef trim (ca. 3 log CFU/g) and placed in a randomized bin sector.  The combo was then filled with non-inoculated beef trim. Sampling methods were N-60 surface excision, N-90 surface excision, N-60 core drill shaving, Cozzini core sampler, and purge. Meat samples (375 g composites) were combined with 1.5 L of mEHEC and enriched at 42°C for 18 h prior to PCR to determine STEC presence. 

Results: Purge sampling was the most effective method, with 13/14 samples positive.  Cozzini corer, N-60 core drill shaving, N-60 excision and N-90 excision methods resulted in 11/14, 9/14, 7/14 and 7/14 samples being positive, respectively. The purge sampling and Cozzini corer were superior combo sampling methods, because they were able to detect contamination in the lower combo sectors. The N-60 and N-90 excision sampling methods were effective if contamination was placed into one of the top or middle sectors, but only 3/12 samples were positive for bottom sector inoculated samples. 

Significance: Sampling of beef trim is an important component of ground beef safety programs.  Excision sampling of combos utilizing N-60 or greater is commonly utilized.  Selection of a sampling method (purge sampling or deep coring) capable of contacting trim in the bottom half of combos will yield a greater probability of identifying STEC contaminated combos.