Detection of entero- and verocyto-toxin genes in Escherichia coli from diarrhoeal disease in animals using the polymerase chain reaction.

Oligonucleotide primers were designed for the specific polymerase chain reaction (PCR) amplification of the enterotoxins STIa and LTI and of the verocytotoxins VT1 and VT2. All of 184 E. coli isolates from cases of diarrhoea from pigs, cattle and sheep gave identical toxin profiles by PCR and gene probe. Differentiation between VT2 and VT2v was achieved using two oligonucleotide primers pairs in PCR and showed that all of 34 VT2+ porcine isolates, of which 23 were 0138:K1, harboured VT2v whereas 20 VT2+ bovine and ovine isolates harboured VT2. No isolate harboured both VT2 polymorphs. Simplified methods for sample preparation for PCR were examined and showed that PCR was not inhibited by direct addition of broth culture to the reaction mixture.