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Prevalence of EHEC in Retail Ground Beef: Baseline Study Phase 3

This study analyzes 5000 ground beef samples to determine the prevalence of non-O157 EHEC. Challenges in defining EHEC/pSTEC are discussed, and the study highlights the need for improved process control in ground beef production.

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Prevalence of EHEC in Retail Ground Beef: Baseline Study Phase 3

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  1. Prevalence of Enterohemorrhagic E. coli (EHEC) in Marler and Clark Retail Ground Beef Baseline Study: Phase 3Mansour Samadpour

  2. Introduction • IEH has been commissioned by Marler and Clark to conduct a baseline study to determine the prevalence of non-O157 EHEC in ground beef. • The project involves analysis of 5000 ground beef samples purchased at retail markets throughout the country. • IEH accepted the project with the condition that the names of the manufacturing establishments would not be released.

  3. Enterohemorrhagic (EHEC): Pathogenic Shiga Toxin Producing E. coli (pSTEC) • Several other serotypes of EHEC have been associated with HC, and HUS • These serotypes are difficult to test for, mainly due to lack of convenient markers to allow for their detection • Another impediment is lack of regulatory definition for the target organisms

  4. Challenges in Defining EHEC/pSTEC • Up to 20% of ground beef samples at retail can contain E. coli that produce Stx, great majority of these STEC strains lack the ability to cause illness in humans: • Stx is phage borne, generic E. coli can get infected with the phage • Stx alone is not sufficient to produce illness other factors such as eae, or subtilase are needed • All major serotypes of EHEC also contain EPEC members

  5. The IEH Definition • An E. coli strain is deemed to be EHEC/pSTEC if it: • Carries/produces at least one form of Stx • The strain should also be eae or Subtilase positive • All isolates will be serotyped to determine if they belong to one of the common serotypes in the USA (O26, O45, O111, O121, O145) • Other serotypes will also be considered to be EHEC/pSTEC if they possess the appropriate virulence factors

  6. Retail Ground Beef baseline StudyPhase III

  7. Human isolates of non-O157 STEC, by serogroup, 1983-2002 % of isolates N = 940 isolates 55 O groups, each <1% 70% Brooks, JID 2005;192:1422

  8. Conclusions regarding Phase III • Substantial number of positives have the Subtilase/Stx genotypes • We have found some of the more pathogenic serotypes which are not included in the CDC-6 • From a public health point of view the CDC-6 approach is flawed • The results of the current study are based on N=1 sampling plan, as such, the data is an underestimation of the burden of the target organisms

  9. Effective use of the pSTEC group • Process control • Process control • Process control • Our failure to control pathogens in ground beef is due to: • Lack of understanding the microbiological aspects of the process • Insufficient verification • Lack of process control

  10. Frequency of Positive Signals in Carcasses, Ground Beef, Trim, and Variety Meats

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