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<OL> <LI> To determine the prevalence of Escherichia coli O157:H7 in downer and control (non-culled) dairy cattle from the Upper Midwest; <LI> To ascertain the genomic variability (PFGE) and the antibiotic-resistance proiles of the serotype O157:H7 isolates from downer and control cattle; <LI> To clone and seuence the antibiotic resistance determinant(s) and segments adjacent to the resistance elements to assess relatedness and origin.
During the initial 12-18 months, 400 colon and fecal samples will be collected from approximately 200 downer diary cattle and 200 healthy dairy cattle, at slaughter. The latter group will be used as a control group. The samples will be tested for E. coli O157:H7 using enrichment, immunomagnetic separation, and selective plating following standad procedures. Confirmed isolates of E. coli O157:H7 will be genomically subtyped using pulsed field gel electrophoresis (PFGE) and screened for resistance to antibiotics. The PFGE profiles will be used to determine the genomic relatedness of the O157:H7 isolates from downer and control cattle. The antibiotic-resistance determinants from different PFGE subtypes (clades) will be cloned and sequenced. The DNA sequence data will be compared by both local and global alignments to address their origin(s). Results from the proposed study will generate data useful in risk assessment determinations for ground beef and E. coli O157:H7.