An official website of the United States government.
1. To determine the prevalences and quantitative levels of RAJ colonization among individual
cattle and assess the respective degrees of pen to pen variation. <P>
2. To determine if the E. coli O157:H7 status of cattle within a pen is related to the presence of
individual high-level RAJ-colonized cattle within that pen.<P>
3. To determine if RAJ swabbing represents a more sensitive means of identifying E. coli
O157:H7 positive cattle prior to slaughter.
Findings: The recto-anal junction (RAJ) may represent an important site for bovine E. coli O157:H7 colonization. Some feedlot cattle, termed super-shedders, were found to be significantly colonized at the RAJ, as determined by E. coli O157:H7 prevalence, count and persistence. E. coli O157:H7 RAJ colonization correlated to fecal excretion, and genetic fingerprinting indicated that RAJ and fecal strains were linked. Significant pen-pen variation in RAJ and fecal prevalence was observed, and genetic fingerprinting indicated that E. coli O157:H7 within feedlot pens are more similar than isolates from different pens, suggesting that pens act as independent units with respect to E. coli O157:H7 epidemiology. Levels of E. coli O157:H7 colonization and excretion among cattle were significantly higher if there was a super-shedder in their pen, and isolates from super-shedders and their pen-mates were closely related. Super-shedders appear to play an important role in influencing the excretion of E. coli O157:H7 by feedlot cattle. RAJ swabbing was a more sensitive means of determining an animal's or pen's E. coli O157:H7 status than fecal sampling. Identification of super-shedders may be the basis for management strategies and specific interventions aimed at minimizing carcass contamination at slaughter and bovine transmission of E. coli O157:H7 pre-slaughter.