Project Summary

Detection of Escherichia coli O157:H7 in Frozen Retained Product Using a Greatly Increased Sample Size

Principle Investigator(s):
W. P. Pruett and R. Flowers
Silliker Laboratories Group, Inc.
Completion Date:
September 1999


Layman’s Summary 

A study was conducted to determine if existing on-line sampling methods were sufficient to detect E. coli O157:H7 in ground beef and if a more aggressive sampling (larger sampling units) would increase the chance of detecting the pathogen in frozen patties. The study also determined whether genetic screening technologies were better for detecting the pathogen than standard testing procedures and if non-pathogenic indicator organisms could be used to predict pathogen contamination. 

A large batch of naturally contaminated frozen ground beef patties, that were detected using a routine on-line sampling plan was further sampled for the pathogens using a larger sample size. A total of 710 samples were tested using a larger sample size and three new testing methods. A total of 47 samples were found through confirmed culture techniques to contain the pathogen. The genetic screening test detected 29 of these, which was higher than the other two testing procedures.    

The routine, on-line sampling plan was sufficient for detecting the pathogen in ground beef batches where there was a higher incidence of E. coli O157:H7 in the sample lot. However, a more aggressive sampling procedure was required to detect the pathogen where the incidence rate was lower. It also suggests that genetic based testing procedures are necessary, along with larger sample sizes, to detect lower levels of the pathogen and to detect them more consistently.