June 1, 2011
Texas Tech University graduate students recently went shopping in 32 cities in 28 states for the kind of non-O157 toxin-producing escherichia coli now killing people in Europe.
While they did not find the rare serotype wreaking havoc in northern Europe, what they did find should be enough to concern Americans.
TTU graduate student Jessie L. Vipham and his colleagues collected samples from ground beef and whole-muscle beef cuts to test for the prevalence of non-O157 Shiga toxin-producing E. coli (STEC), Campylobacter and Salmonella.
All totaled, the TTU shoppers collected enough beef between February and May 2011 for 2,915 samples.
Non-O157 STEC antigens, like the deadly O104:H4 pathogen associated with the outbreak in northern Europe, were found in 5.9 percent of the beef samples.
"Whole muscle cuts had a prevalence of 4.11 percent and ground beef samples prevalence was 6.99 percent," Vipham wrote for his master's thesis in Animal Science.
The non-O157 serotypes found in the beef were some of the better known ones in the United States, including O26, O145, O103, and O111. While fairly common, these E. coli strains are not defined as "adulterants" by USDA's Food Safety and Inspection Service (FSIS) and therefore are allowed in meat.
Among all E. coli strains, only O157:H7 is legally considered an adulterant -- a poison -- in meat and therefore not tolerated by FSIS inspectors.
The TTU study, which will be presented at the International Association for Food Protection's (IFP's) annual conference later this summer in Milwaukee, also found Campylobacter in 9.3 percent of the samples, with 17.24 percent in whole muscle cuts and 7.35 percent in ground beef.
Salmonella was present in 0.65 percent, with 1.02 percent found in whole cuts and 0.54 percent in ground beef.
Since October 2009, FSIS has been sitting on a petition filed on behalf of victims of non-O157 Shiga Toxin-producing E. coli to declare six more strains as adulterants. In addition to the four strains found in beef by TTU, the petition requests that 0121 and 045 be kept out of meat.
"Creating pathogen baselines in U.S. retail beef is imperative for targeting interventions for pathogen control," Vipham wrote.
Original article by Dan Flynn
Response Submitted by:
Dr. Mindy Brashears
Dr. Guy Loneragan
Dr. Mark Miller
Thank you for your interest in the research being currently studied within the Food Safety and Public Health program at Texas Tech University. We strive to conduct the best research possible that advances our knowledge and understanding among our field and can be translated and applied to enhance the safety of our food supply. Given this, we are concerned that you may have misinterpreted our research in a manner that is inaccurate and misleading and may confuse this critically important issue. We take our role in the food safety continuum very seriously and have concerns when our research is interpreted in a manner that may not be accurate and also be misleading.
Jessie Vipham was a graduate student in the Department of Animal and Food Sciences at Texas Tech University who successfully graduated in May of this year with her M.S. degree; as such, her thesis has officially been published by the university and is available for download from the Texas Tech University Library (http://dspace.lib.ttu.edu/etd/handle/2346/ETD-TTU-2011-05-1540). Additionally, Ms. Vipham has had an abstract accepted for presentation at IAFP that will summarize the findings of her study.
The article states, “Texas Tech University graduate students recently went shopping in 32 cities in 28 states for the kind of non-O157 toxin-producing Escherichia coli now killing people in Europe.” This is not an accurate statement on two accounts. First of all, the evaluation of samples was of a small subsample from this much broader nationwide study of beef where she developed a baseline for Campylobacter and Salmonella, not STECs. The small subset of samples contained 252 ground beef and 73 whole muscle cuts from the larger “nationwide baseline” sample group consisting of 2,230 ground beef and 686 whole muscle cuts. Secondly, we did not analyze the samples for the presence of E. coli O104:H4, the strain associated with the current outbreak in Europe.
The article also states that, “Non-O157 STEC antigens, like the deadly O104:H4 pathogen associated with the outbreak in northern Europe, were found in 5.9 percent of the beef samples”. In Ms. Vipham’s exploration of the small subsample, she used rtPCR to detect genetic targets that differentiate among serotypes: O145, O26, O111, O103, O121, O91, O113, and O45. In the first sentence of the results section, she states, “It is important to note that these isolates have not tested positive for pathogenicity.” The isolates have not been analyzed for the virulence markers but rather only for the genes encoding O antigens.
It is also important to note that it was not the purpose of her small subsample study to try and recover STEC but rather to provide a preliminary look to see if it warrants systematically exploring STEC analyses on remaining ground beef/whole muscle samples to determine prevalence within our study. As co-authors, we think that the preliminary study indicates that a more thorough exploration is warranted to provide the industry with hard data on which they can use. The further analyses would include screening all ground beef samples for the presence of non-O157 STECs and evaluating any presumptive positive samples for the presence of virulence genes.
One additional point of clarification is that many of the statements made in the article that are said to be “reported by Texas Tech” are in fact part of a comprehensive literature review in the thesis. The prevalence data on human food-borne disease outbreaks as well as data representing prevalence of pathogens in other countries was not collected by TTU scientists, but rather included in the thesis as a point of reference to put Ms. Vipham’s data in context.