T9-06 The Use of Novel Prevalence Calculation Methods To Estimate Pathogen Prevalence in Raw Ground Beef and Beef Manufacturing Trimmings Regulated by the Food Safety and Inspection Service

Tuesday, August 2, 2016: 2:45 PM
241 (America's Center - St. Louis)
Stephen W. Mamber, U.S. Department of Agriculture-FSIS, ODIFP, Washington, DC
Michael Williams, U.S. Department of Agriculture-FSIS, Risk Assessment Division, Fort Collins, CO
Patrick Smith, U.S. Department of Agriculture-FSIS, ODIFP, Washington, DC
Jeremy Reed, U.S. Department of Agriculture-FSIS, ODIFP, Washington, DC
Christopher Aston, U.S. Department of Agriculture-FSIS, ODIFP, Washington, DC
Jennifer Highland, U.S. Department of Agriculture-FSIS, ODIFP, Washington, DC
Marina Drozdovitch, Data and Analytic Solutions, Inc. (DAS), Fairfax, VA
Sarah Hay, U.S. Department of Agriculture-FSIS, ODIFP, Washington, DC
Nelson Clinch, U.S. Department of Agriculture-FSIS, ODIFP, Washington, DC
Introduction: FSIS developed a novel method that incorporates its verification testing results and improved volume data to estimate the prevalence of Escherichia coli O157:H7, non-O157 Shiga toxin-producing E. coli (STEC) and Salmonella sp. in raw beef products. FSIS has defined prevalence as the proportion of 325-gram beef sample units that would test positive for a bacterial pathogen if the entire United States production were sampled and analyzed during a specified time period.

Purpose:  To estimate pathogen prevalence in raw ground beef and beef manufacturing trimmings (MT43 and MT60 sampling projects, respectively) from raw beef producing establishments using fiscal year 2015 sampling data.

Methods: FSIS collected and analyzed ground beef (MT43) and beef trim (MT60) samples for each pathogen. To estimate pathogen prevalence, the annual production data (average daily volume x production days per month x 12) generated for each establishment by FSIS inspection personnel were used. This avoided stratifying samples into volume groups. Calculations took collected sample weights into account. Prevalence was then calculated as (sum(contaminated volume))/(sum(total volume)).

Results: FSIS analyzed 11,682 MT43 samples collected from 1,180 establishments and 3,277 MT60 samples collected from 426 establishments.  Prevalence of E. coli O157:H7 and Salmonella sp. in MT43 samples was 0.05% (95% confidence intervals [CI],  0.01-0.20%) and 2.85% (95% CI, 1.79-4.52%), respectively.  Prevalence of E. coli O157:H7, non-O157 STEC and Salmonella sp. in MT60 samples was 0.13% (95% CI, 0.02-0.81%), 0.47% (95% CI, 0.21-1.04%) and 1.66% (95% CI, 0.95-2.90%), respectively. 

Significance: FSIS successfully developed and used novel prevalence calculation methods to estimate pathogen prevalence in regulated products. These estimates inform policies relevant to the prevention of pathogen contamination of raw beef products in FSIS-regulated facilities, and to monitor changes over time. This approach has been adapted for use in estimating pathogen prevalence and volume-weighted percent positive results in other regulated commodities (e.g., poultry products).