Table 3.

Isolation and characterization of O157 VTEC strains from additional samples collected at the four Dutch dairy farms investigated in the follow-up study

FarmDate of samplingNo. of samples O157 VTEC positive/no. of samples tested
CattleaPigsHorsesPoniesSheepStable fliesMilk filterSilageAnimal drinking water
IISept 19961b/2c 0/1
Dec 19961d/1
Mar 19970/10/40/10/10/1
Jun 19970/10/20/1
Sept 19970/13e/3c 1e/11e/11e/10/1
Nov 19970/20/30/10/10/20/2
VOct 1996f 0/101g/11g/10/20/1
Jan 1997h 0/2i 0/64g/50/10/3
Apr 19970/3j 0/30/50/1
Jun 19971k,l/50/51l/40/1
Sept 19970/5m 0/40/10/1
Nov 19971n/70/50/20/90/10/2
VIIINov 19960/150/10/10/1
Jan 19970/10/1
Apr 19970/10/50/10/1
Jul 19970/50/10/1
Sept 19970/10/30/10/10/1
Nov 19970/50/10/10/1
XNov 19960/70/10/10/1
Feb 19970/40/10/10/1
Apr 19970/30/10/1
Sept 199714o/180/40/10/2
Nov 19970/10/10/1
  • a Fecal samples from cattle which could not be identified individually since either the cattle wore no ear tag numbers or the samples were taken from fresh droppings in farm building (adult steers) or in pastures (heifers).

  • b The isolate was characterized as being phage type 8, Vero cell assay positive, VT1 positive, VT2 positive,eae positive, and PFGE pattern D.

  • c Including one fowl.

  • d The isolate was characterized as being phage type 32, Vero cell assay positive, VT1 positive, VT2 positive,eae positive, and PFGE pattern S.

  • e The isolates were characterized as being phage type 21, Vero cell assay positive, VT1 negative, VT2 positive,eae positive, and PFGE pattern K.

  • f Additionally, fecal samples from a dog, a rabbit, and the pig’s dung were collected. All tested negative.

  • g The isolates were characterized as being phage type 14, Vero cell assay positive, VT1 negative, VT2 positive,eae positive, and PFGE pattern G.

  • h Additionally, fecal samples from a dog and the pig’s dung were collected. Both tested negative.

  • i Including one adult steer.

  • j All adult steers.

  • k An adult steer.

  • l The isolate was characterized as being phage type 14, Vero cell assay positive, VT1 negative, VT2 positive,eae positive, and PFGE pattern N.

  • m Including three steers.

  • n Sample taken from a fresh dropping in the pasture. The isolate was characterized as being phage type 14, Vero cell assay positive, VT1 negative, VT2 positive, eaepositive, and PFGE pattern N.

  • o Samples taken from fresh droppings in the pasture. Twelve of the isolates were characterized as being phage 34, Vero cell assay positive, VT1 negative, VT2 positive, eaepositive, and PFGE pattern Q, and the remaining two were characterized as being phage type 2, Vero cell assay positive, VT1 negative, VT2 positive, eae positive, and PFGE pattern T.