Real-time PCR for differentiation of F4 (K88) variants (F4ab, F4ac, F4ad) of enterotoxigenic Escherichia coli from diarrhoeic piglets

A one-step real-time PCR using one set of oligonucleotide primers and three probes was developed for differentiation of F4 (K88) variants (F4ab, F4ac, F4ad) of enterotoxigenic Escherichia coli (ETEC) from diarrhoeic pigs. The limits of detection of F4ab, F4ac and F4ad in broth dilution were 106, 105 and 104 colony forming units (CFU)/mL, respectively. In faecal samples spiked with E. coli, the limits of detection of F4ab, F4ac and F4ad were 106, 106 and 104 CFU/g faeces, respectively, without enrichment and 103, 102 and 102 CFU/g faeces following enrichment. In 42 ETEC field isolates from pigs in Korea encoding the F4 gene, all were identified as the F4ac variant.