Development and evaluation of oligonucleotide DNA probes for detection and genotyping of Shiga-like toxin producing Escherichia coli

Use of antisense oligonucleotide probes (OP) for detection and genotyping of Shiga-like toxin producing Escherichia coli (SLTEC) was evaluated. Based on published deoxyribonucleic acid (DNA) sequences of the A subunits of Shiga-like toxin (SLT) I and II genes, three synthetic antisense OP were constructed (OP- and 1, -2 and -3). Their use for detection and genotyping of SLTEC was evaluated and the results were compared to those obtained using cloned toxin-gene probe fragments. Both the OP-1 and OP-2 hybridized with all 69 SLT-I and II producing strains. Furthermore, the OP-1 hybridized only with all 18 SLT-I-only producing strains, and the OP-2 hybridized only with all 48 SLT-II-only producing strains. OP-3, a pool of four OP, detected all SLTEC strains regardless of toxin genotype. None of the OP hybridized to any of the 91 SLT-negative strains. These results demonstrate the three OP to be unique reagents for SLTEC epidemiological studies