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 respec t to receptor binding specificity, presence of the aerobactin system, production of colicin V, resistance to the bactericidal effects of ser um. Although most F165-positive isolates shared similar DNA sequences with pap operon sequences, less than half of these isolates demonstrat ed 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 respecti vely. Certain F165-positive isolates sharing similar DNA sequences wit h both pap and sfa operon sequences demonstrated mannose-resistant hem agglutination of sheep erythrocytes, as observed in human uropathogeni c E. coli possessing the prs operon. Most isolates caused mannose-resi stant, neuraminidase-resistant hemagglutination of human, equine, feli ne, and bovine erythrocytes. Thus, F165-positive isolates express one or more adhesins with different receptor binding specificities. An ass ociation was observed between the various receptor binding specificiti es and serogroup. Most F165-positive isolates possessed the aerobactin system and were resistant to the bactericidal effects of serum, but o nly 38.5% isolates produced colicin V.