Development of verotoxin 2- and verotoxin 2 variant (VT2v)-specific oligonucleotide probes on the basis of the nucleotide sequence of the B cistron of VT2v from Escherichia coli E32511 and B2F1

Abstract

We and others have noted that there are serological differences between verotoxin 2 (VT2) (also known as Shiga-like toxin II) produced by Escherichia coli C600(933W) and the VT2 variant (VT2v) produced by strain E32511. Recent reports have described nucleotide sequence differences between the VT2v B subunit cistron of E32511 and B2F1 and that of VT2. We have confirmed the sequence differences and have used them to design oligonucleotide probes which differentiate the B subunit cistron of VT2v from that of VT2. Isolates of VT-producing E. coli obtained from human as well as food and veterinary sources were classified according to the toxin phenotype by using a toxin neutralization assay with VT2-specific monoclonal antibody and VT2v-specific polyclonal antisera. Using the oligonucleotide probes in colony hybridization, we detected 35 of 35 VT2 producers and 16 of 16 VT2v producers. One VT2 producer was falsely identified as containing the VT2v gene. The E32511 strain in our collection hybridized only with the VT2-specific probe. Southern hybridization of radiolabeled oligonucleotide probes showed that strains carried zero to one copy of the VT2 gene and zero to two copies of the VT2v gene. We conclude that colony hybridization with the VT2-and VT2v-specific probes is highly predictive of the toxin phenotypes in the clinical isolates described in this study.

Comparison between a PCR-ELISA test and the vero cell assay for detecting Shiga toxin-producing Escherichia coli in dairy products and characterization of virulence traits of the isolated strains

“…Regarding the virulence traits obtained for 34 strains of STEC isolated from naturally-contaminated samples, the data suggest that some variants occurred, which is in agreement with the increasing number of variants recently described in the literature (Gyles et al 1988;Weinstein et al 1988 9 ; Gannon et al 1990;Ito et al 1990;Hii et al 1991;Paton et al 1992Paton et al , 1993cLin et al 1993b, b;Kim et al 1997;Pierard et al 1998 10 ). These variants were usually described as Stx2 strains of STEC, while variants derived from Stx1 strains are rarely reported (Paton et al 1993a(Paton et al , 1995a.…”

Subtyping of Shiga toxin 2 variants in human-derived Shiga toxin-producing Escherichia coli strains isolated in Japan

“…Eight of them possessed stx1 and stx2 genes, and one possessed stx2 and G1 genes. Similar differences in Stx2 variant distribution were also reported by Thomas et al [23], Tayler et al [24], and Hii et al [15]. It is interesting that the oldest strain in our collection, isolated in 1986, possessed stx2 and G1 genes, and that the G1 gene was present in most of the prefectures in Japan.…”

“…However, variable and con£icting results have been reported with regard to the prevalence of Stx2 variants. While Tyler et al reported that all seven E. coli O157:H7 isolates contained stx2vha [14], Hii et al did not ¢nd the Stx2 variant pheno^genotype in any of their 23 E. coli O157:H7 strains [15]. Ru « ssmann et al reported that 17 of 38 strains from HUS patients possessed stx2c [16], and Nishikawa et al reported that 61 of 169 E. coli O157 strains isolated in Japan possessed stx2vha [17].…”

The specific activities of Shiga-like toxin type II (SLT-II) and SLT-II-related toxins of enterohemorrhagic Escherichia coli differ when measured by Vero cell cytotoxicity but not by mouse lethality

“…These SLT-II group members include SLT-Ilvha (VT2vha), SLT-Ilvhb (VT2vhb), and SLT-IIc, all of which are nearly 97% homologous to SLT-1I at the deduced amino acid sequence level (14,45). Other SLT-II-related toxins have been described (8,12,21,30,37,44,54,59), but many of these toxins were detected by PCR analysis and only a few have been isolated and sequenced.…”