Virulence factors associated with F165-positive Escherichia coli strains isolated from piglets and calves.

In this study, 91 F165-positive Escherichia coli isolated from calves and piglets with diarrhea or septicemia were characterized with respect to receptor binding specificity, presence of the aerobactin system, production of colicin V, resistance to the bactericidal effects of serum. Although most F165-positive isolates shared similar DNA sequences with pap operon sequences, less than half of these isolates demonstrated MRHA to P antigen of human red blood cells and Forssman antigen of sheep red blood cells recognized by P and F (or Prs) adhesins respectively. Certain F165-positive isolates sharing similar DNA sequences with both pap and sfa operon sequences demonstrated mannose-resistant hemagglutination of sheep erythrocytes, as observed in human uropathogenic E. coli possessing the prs operon. Most isolates caused mannose-resistant, neuraminidase-resistant hemagglutination of human, equine, feline, and bovine erythrocytes. Thus, F165-positive isolates express one or more adhesins with different receptor binding specificities. An association was observed between the various receptor binding specificities and serogroup. Most F165-positive isolates possessed the aerobactin system and were resistant to the bactericidal effects of serum, but only 38.5% isolates produced colicin V.