Purpose: To estimate the prevalence of E. coli O104 in feedlot cattle feces and characterize the isolated strains.
Methods: A total of 757 cattle rectal content samples, representing 29 different feedyards, were collected at a slaughter plant. Fecal samples were enriched in E. coli broth for 6 hrs at 40°C. DNA extracted from pre and post enriched fecal samples were tested by a multiplex PCR to detect serogroup O104 and associated virulence genes of the hybrid strain. Post-enriched fecal samples were also subjected to culture-based method of detection, which involved immunomagnetic separation with O104 beads, plating on selective chromogenic medium, followed by serogroup confirmation by PCR of pooled and individual colonies. Pure cultures of O104 were characterized by multiplex PCR assays to determine virulence genes and flagellar types.
Results: Of the 757 samples, 38 (5%) were positive before enrichment and 349 were positive (46%) after enrichment of fecal samples for O104 serogroup specific gene. We obtained 143 O104 isolates by culture-based method of detection, of which 65 of them were positive for terD, 16 were positive for hlyA and 16 for stx1genes. O104 isolates harbored diverse flagellar (H) antigens, 45 isolates were positive for H21, 38 for H11, 37 for H7 and 5 for H2 antigens. Ninety-two of the isolates were also found positive for O8/O9 antigen genes.
Significance: Cattle harbor and shed E. coli O104 in feces, but only a few strains (11.18 %) carried stx1 gene. None of the isolated strains carried genes characteristic of enteroaggregative type.