An official website of the United States government.
Outbreaks of food-borne illness linked to consumption of hamburger contaminated with E. coli
O157:H7 have had a devastating effect on profitability of the beef industry. Although we have
established that the prevalence of E. coli O157:H7 on the hides of fed cattle entering Midwestern
packing plants is high, little is known about the prevalence of E. coli O157:H7 across other
regions of the country. Circumstantial evidence from the incidence of meat recalls suggests that
the prevalence of E. coli O157:H7 is greater in some regions of the country than others. Thus,
the proposed experiment is designed to establish the prevalence of E. coli O157:H7 on the hides
and carcasses of feedlot-finished cattle in seven cattle feeding regions.
<P> The objectives of this study were as follows: <br/>
1. Determine if there are regional differences in the prevalence of E. coli O157:H7 on the
hides and pre-evisceration carcasses of feedlot-finished cattle. <br/>
2. Determine if there are unique E. coli O157:H7 pulsed-field gel electrophoresis patterns
for isolates obtained from the hides of cattle originating from individual feedlots or
geographical regions.
Findings:
2591 samples of both hides and pre-evisceration carcasses were collected from nine packing plants located in major cattle-producing regions of the U.S. Prevalence for E. coli O157:H7 in samples of the animal hides ranged from 9% at one plant to 85% at another. While the differences in prevalence between some plants were statistically significant, we do not believe that these differences are due to regional effects. The reason for this belief comes, in part, from the day-to-day variation observed in sampling. Large fluctuations (79% to 27%) in E. coli O157:H7 prevalence in hide samples occurred from one day to the next. Every plant except one had at least one sampling day where the hide prevalence of E. coli O157:H7 was over 60%. The one plant being the exceptional was sampled for a previous study and found to have hide prevalence for E. coli O157:H7 over 80%.<P>
Another point of interest were the transfer rates of E. coli O157:H7 from hide to the carcass surface. The pre-evisceration carcass prevalence for E. coli O157:H7 ranged from 8% to 55% but did not mirror the hide prevalence fluctuations. Some plants did better at not transferring the pathogen from the hide to the carcass surface. This is likely to be a reflection of the carcass dressing practices employed at the individual plants. <P>
Over 3000 E. coli O157:H7 isolates were collected from hide samples for use in PFGE analysis. The PFGE patterns for over 450 of these isolates have been processed and recorded. This report will be updated upon completion of analysis of the remaining isolates.