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Due to its significance to public health, its potential impact to beef trade and production security,
as well as negative public perception issues, E. coli O157:H7 is a critical problem for the beef
industry. Pathogen reduction through a series of interventions at various stages of the beef
production process is currently considered the most effective means to reduce the risk of final
product contamination. Control of E. coli O157:H7 at the pre-slaughter/harvest level is an
important component in such a risk reduction strategy.
<P> A previous checkoff-funded study examined the phenomenon of recto-anal junction (RAJ)
colonization of cattle by E. coli O157:H7. This study concluded that the RAJ does indeed appear
to be a significant site for E. coli O157:H7 colonization, and that this colonization is associated
with fecal excretion patterns. Tied to the phenomenon of RAJ colonization is the concept that
certain cattle within feedlots are colonized by E. coli O157:H7 more frequently, persistently and
in greater numbers than other cattle. These �super-shedders� appear to influence the degree of E.
coli O157:H7 colonization of other cattle in their pens, as well as environmental contamination
levels. While the previous study showed increased levels of E. coli O157:H7 colonization of copenned cattle, it could not confirm that the presence of super-shedders were the cause.
Furthermore, increases in environmental concentrations of E. coli O157:H7 could not be tied
directly to the presence of a super-shedder. <P>
The objectives of this study were as follows: <br/>
1. Demonstrate that the addition/removal of a super-shedder results in an increase/decrease
in the prevalence, mean count and duration of E. coli O157:H7 by other cattle in that pen; <br/>
2. Use genetic similarity profiling to confirm the transmission of E. coli O157:H7 from
super-shedder cattle to other cattle in that pen; <br/>
3. Demonstrate an association between the presence of a super-shedder in a pen and the
prevalence and identity of E. coli O157:H7 in the pen environment.
Findings: Overall, �super-shedders� appear to influence the degree of E. coli O157:H7 colonization of
other cattle in their pens. When super-shedders are introduced to pens with low levels of E. coli
O157:H7 activity, the prevalence and persistence of E. coli O157:H7 colonization increases
among other cattle in that pen. Similarly, levels of environmental contamination appear to
increase as well.