ISOLATION AND CHARACTERIZATION OF VEROCYTOTOXIN-PRODUCING ESCHERICHIA-COLI O157 STRAINS FROM DUTCH CATTLE AND SHEEP

In the periods from July to November 1995 and 1996, fecal samples from Dutch cattle and sheep were collected at the main slaughterhouses of The Netherlands, located at different geographic sites, The samples we re examined for the presence of verocytotoxin (VT)-producing Escherich ia coil (VTEC) of serogroup O157., E., coli O157 strains could be isol ated from 57 (10.6%) of 540 adult cattle, 2 (0.5%) of 397 veal calves, 2 (3.8%) of 52 ewes, and 2 (4.1%) of 49 lambs, Immunomagnetic separat ion with O157-specific-antibody-coated beads appeared to be significan tly more sensitive than conventional plating for detection of the orga nism in feces, With the exception of two isolates from adult cattle wh ich appeared to be negative for VT genes, all animal isolates were pos itive for both VT (VT1 and/or Vn) and E., coli attaching-and-effacing gene sequences, and therefore, they were regarded as potential human p athogens, Although genomic typing by pulsed-field gel electrophoresis revealed a wide variety of distinct restriction patterns, comparison o f tile 63 animal isolates with 33 fecal O157 VTEC strains previously i solated from humans with the diarrhea-associated form of the hemolytic -uremic syndrome by their phage types and VT genotypes showed a marked similarity between animal and human isolates: 30 (90.9%) of the 33 hu man isolates appeared to be of E., coil O157 strain types also isolate d from cattle and sheep, It was concluded that Dutch cattle and sheep are an important reservoir of E. coli O157 strains that are potentiall y pathogenic for humans.