DNA probes for the detection of toxin genes in Escherichia coli isolated from diarrhoeal disease in cattle and pigs.

DNA gene probes specific for genes coding for heat labile toxin (LT), heat stable toxins (STpa, STpb) and Vero-cell toxins (VT1, VT2) were used to examine 1031 diarrhoeal disease isolates of E. coli (345 from cattle and 686 from pigs). Of the bovine strains, 60 hybridized with the STpa probe and most possessed the K99 (F5) or F41 adhesin. Five bovine strains possessed STpb genes and five either VT1 or VT2 genes. Of the porcine strains, 245 hybridized with one or more gene probes. Of 160 K88 (F4) positive strains, 133 possessed both LT and STpb genes, whilst 17 possessed LT or STpb or STpa alone or in combination. Ten K88 strains did not possess toxin genes. Isolates bearing the K99 (F5) adhesion possessed either STpa, STpb and VT2 genes alone or in combination; in one isolate only the LT gene was detected. Isolates belonging to serogroup 0138:K81 were more heterogeneous as to their toxin genes; of the 60 strains, fourteen carried only VT2 genes, thirty-two carried VT2, STpa and STpb genes, one carried LT, VT2, STpa and STpb genes, two carried STpb gene, four carried STpa and STpb genes, one carried LT and VT2 genes, two carried LT and STpa genes, whilst four carried none. Twenty-four percent of all toxigenic strains apparently did not possess adhesins.