P1-44 Distribution and Detection of Shiga Toxin-producing Escherichia coli (STEC) during Large-scale Grinding of Beef Trim

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
Manpreet Singh, Auburn University, Auburn, AL
Rachael Sullivan, Kansas State University, Manhattan, KS
Susan Hettenbach, Kansas State University, Manhattan, KS
Nicholas Baumann, Kansas State University, Manhattan, KS
John Wolf, Kansas State University, Manhattan, KS
Nicholas Sevart, Kansas State University, Manhattan, KS
Minto Michael, Kansas State University, Manhattan, KS
Nigel Harper, Kansas State University, Manhattan, KS
Donka Milke, Kansas State University, Manhattan, KS
Casey Paddock, Kansas State University, Manhattan, KS
Carla Schwan, Kansas State University, Manhattan, KS
Andre Senecal, U.S. Army Natick RDE Center, Natick, MA
Introduction: It is important to understand Shiga toxin-producing Escherichia coli(STEC) distribution and our ability to detect contamination during ground beef manufacturing if a portion of contaminated beef trim enters the process. 

Purpose: Utilize a high-level biocontainment processing facility containing industry-scale beef grinding equipment to conduct inoculated studies to characterize distribution of contamination, and our ability to detect the contamination, during ground beef manufacturing.

Methods: A cocktail of STEC serotypes (O26, O111, O45, O103, O121 and O145) was inoculated onto a 908 g piece of beef trim (yielding 8.9 and 5.8 log CFU/g of the inoculated trim for runs 1 and 2, respectively).  This inoculated portion was placed into a commercial grinder followed by grinding two combos of beef trim.  The meat was ground, blended, re-ground and chub packaged.  Samples (375 g) were collected sequentially after each 45 kg portion of first grind, and every 20thfive-pound chub. Samples were enriched and STEC presence was determined using PCR.

Results: Run 1 (high inoculation level) samples were STEC positive at all sampling points.  For run 2 (low level), 16 of the first 17 samples from first grind were positive and only one of the remaining 15 samples was positive.  Run 2 chub samples were mostly negative (30/34). 

Significance: Initial level of STEC contamination of isolated portions of beef trim entering a grinder greatly impacts the distribution levels and our ability to detect contamination in final chub packages. When a portion of trim is heavily contaminated and ground/blended/packaged, as in run 1, the entire system becomes contaminated and all samples are positive by PCR.  At a lower contamination level, contamination in the grinder appears to dilute STEC to below detection after approximately one combo being ground; however, the blending and packaging process results in further dilution and yields only sporadic positives in finished chubs.