The American Meat Institute (AMI) reported a few days ago that new federal data show that E. coli O157:H7 is found in less than one quarter of one percent of ground beef samples, a 72 percent decline since 2000 in ground beef samples testing positive for the pathogen.
The data are from Food Safety and Inspection Service’s (FSIS) 2010-year end results of microbiological samples of raw ground beef products analyzed for E. coli O157:H7. In 2010, there were 29 positive samples out of 11,616 taken in federal plants, no positives of 905 samples taken in retail stores and one positive out of 29 imported samples. The overall prevalence rate was 0.24 percent. The year-end data is available here.
According to the FSIS, criteria for sampling and analytical methodology for E. coli O157:H7 testing can be drawn from Agency guidance published in August 2008 Draft Compliance Guideline for Sampling Beef Trimmings for E. coli O157:H7 and Draft Guidance for Small and Very Small Establishments on Sampling Beef Products for E. coli O157:H7, and the Federal Register notice on FSIS testing methodology.
The sampling and testing comparison standards for ground beef product and beef manufacturing trimmings are N60 sampling for trim, testing most of the sample (or at least 325 grams) in the lab, and applying a screening or culture method designed and validated for detecting the lowest possible levels of sub-lethally injured E. coli O157:H7 cells.
The real question is whether taking more samples (greater than N60) and testing more often would continue to show this positive development. Despite AMI’s hopeful trend, there are strong voices suggesting that the sampling is in fact inadequate.
Dr. Richard Raymond, former Undersecretary of Agriculture for Food Safety, recently e-mailed me the following:
“Testing methodologies used in 2000 are far different than methods for sampling used in 2010. This is comparing apples and oranges, and it fails to mention that industry began testing its own products at its own costs (a very good thing) and those positives are diverted to cooking or rendering. Those positives are not included in the 0.24% AMI is so proud of. And, FSIS for years did not test that lot if industry had already found a positive, producing a falsely low number for prevalence.
“AMI, what is the incidence of O157 if all positives are counted, not just FSIS positives after product has been diverted? That is the true incidence. And, AMI, if you are so proud of 0.24% positive for O157, how can you continue to ignore pleas to make non-O157 STECs an adulterant in ground beef when they test positive in ground beef samples 2.0% of the time?”
I got another email from Barbara Kowalcyk, CEO & Director of Research and Public Policy at the Center for Foodborne Illness Research & Prevention:
“Every year when FSIS releases its microbiological testing data, the meat industry tries to use that data to say that the prevalence of pathogens in meat and poultry products has gone down. I have criticized this inappropriate use of statistics every time for many of the reasons that Dr. Raymond pointed out. These programs were not statistically designed to estimate prevalence and making year-to-year comparisons are like comparing apples and oranges.
“Considering the relatively insignificant number of samples collected (compared to the millions and millions of product produced) and the uneven distribution of pathogens in meat and poultry products, getting a positive is like finding the needle in the haystack or hitting the lottery. Either you were very lucky to find the hotspot or, more likely, there were so many hotspots that it was easy to find one.
“Basically, the lower the prevalence rate, the more you have to look to confidently say it isn’t there. Remember, absence of evidence is not evidence of absence. At the current number of samples, the testing program lacks any real power to estimate the prevalence – even assuming it is 1% or 2%. So, either FSIS is consistently very, very lucky or the testing program is biased to underestimate the prevalence. Odds are it is the latter.”
So, AMI and FSIS, what is your position?