Evaluation of oligonucleotide probes for identification of shiga-like-toxin-producing Escherichia coli

Abstract

Four synthetic oligonucleotide probes representing different regions of the Shiga-like toxin I (SLT-I) structural genes and one oligonucleotide derived from the SLT-II gene of Escherichia coli serotype 0157:H7 strain 933 were examined for the identification of E. coli strains that produce cytotoxins for Vero or HeLa cells. E. coli strains that synthesize SLT-I alone or 0157:H7 isolates that coexpress SLT-I and SLT-II hybridized with ail four probes that were complementary to the SLT-I genes, suggesting that they have toxin genes with great homology in ail the regions examined. In colony hybridization tests, these oligonucleotide probes did not react with E. coli strains that were nontoxigenic for Vero ceils or that produced cytotoxins belonging to the SLT-II family. The probe derived from the sIt-JIA gene distinguished E. coli strains that produced SLT-II alone from SLT-I-producing strains and hybridized to ail E. coli 0157:H7 strains that produced both SLT-I and SLT-II. Using two of these oligonucleotide probes that were complementary to sIt-IA or sIt-JIA sequences, we identified 50 of 52 cytotoxin-producing strains, whereas none of 416 nontoxigenic E. coli strains was reactive. The colony blot hybridization with the oligonucleotide probes described here can serve as a specific and sensitive test with potential diagnostic value.

Evaluation of Enzyme‐Labeled Oligonucleotide Probes to Identify Enterohaemorrhagic Escherichia coli

“…The use of probes consisting of fragments from structural genes encoding VT1 and VT2 labeled with an isotope (3,14) are usually time-consuming, require specialized facilities and are hazardous. Oligonucleotide probes for VT genes have also been developed (2,8) and shown to have higher specificity for VT genes; the use of these probes is also time-consuming and hazardous due to the isotope labeling. In the place of radio isotopes, digoxigenin has been used to label probes for VT genes (1).…”

Highly conserved B-subunit genes of Shiga-like toxin II variants found in Escherichia coli O157 strains

“…The E. coli O157 strains used in this study, their origin and the diseases they caused are listed in Table 1. The strains were identified either by colony blot hybridization using oligonucleotide probes 772 and 849 as described [15] or by PCR with primers MK1/MK2 [16]. Probe 772 identifies slt-I and probe 849 slt-H and its variant forms [15].…”

“…The strains were identified either by colony blot hybridization using oligonucleotide probes 772 and 849 as described [15] or by PCR with primers MK1/MK2 [16]. Probe 772 identifies slt-I and probe 849 slt-H and its variant forms [15]. Biochemical characterization revealed that all E. coli O157 strains gave a negative sorbitol and /3-glucuronidase reaction.…”

Applications of nucleic acid probes in veterinary infectious diseases

“…Moseley et al (1982) used probes for the first time to identify organisms carrying genes for enterotoxins. Such probes are now routinely being used to determine potential pathogenicity of Escherichia coli by screening for genes of enterotoxins (Moseley et al, 1982;Maddox and Wilson, 1986;Karch and Meyer, 1989).…”