A quartz crystal microbalance method for rapid detection and differentiation of shiga toxins by applying a monoalkyl globobioside as the toxin ligand

A simple globobiosyl (Gb2) ceramide mimic carrying a monoalkyl chain (C18) was applied for a monolayer Langmuir-Blodgett (L-B) technique to detect Shiga toxins (Stxs) by a quartz crystal microbalance (QCM) method. The artificial glycolipid, synthesized from penta-O-acetyl-D-galactopyranose via a conventional glycosidation pathway, was developed at the air-water surface for the formation of the monolayer film. Then, the film was transferred onto a QCM cell surface modified with alkanethiols. Upon the addition of each of Stx-1 and Stx-2, the decrease of frequency reached saturation within 45 min at a few nanogram order per quartz cell. Binding constants (Ka) estimated for each of Stx-1 and Stx-2 showed little difference between the two toxins. On the other hand, in the presence of an artificial acrylamido Gb2 copolymer as a competitive inhibitor, the two toxins showed a large difference in the binding behavior to the L-B monolayer.

Detection of verocytotoxin bound to circulating polymorphonuclear leukocytes of patients with hemolytic uremic syndrome

The epidemic form of hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children and is characterized by a prodromal phase of sometimes bloody diarrhea. The role of verocytotoxin (VT)-producing Escherichia coli has been strongly implicated. Although antibodies against VT have been detected in the serum of patients with HUS, VT itself has never been detected in circulating blood. In this study, VT-2 was detected in the systemic circulation in 9 of 10 patients with the epidemic form of HUS. In those cases, VT-2 was bound exclusively to polymorphonuclear leukocytes (PMN). The detection of VT-2 bound to PMN was associated with the presence of diarrhea at the time the blood samples were obtained. The one patient for whom VT was not detected presented with atypical HUS. For 5 of the 10 patients with HUS who were studied, the time course of VT binding was analyzed; binding decreased in four patients. The finding of VT bound to PMN in the systemic circulation of patients with HUS is important for a clearer understanding of the pathogenesis of HUS and suggests new approaches for treatment in the future.

Virulence genotypes and serotypes of verotoxigenic Escherichia coli isolated from cattle and foods in Argentina. Importance in public health

Virulence factors of Verotoxin-producing Escherichia coli (VTEC) strains isolated from hamburgers and ground beef were studied in Argentina by PCR. Their virulence profiles were correlated with those corresponding to strains isolated from calves and adult cattle. Most virulent profiles (VTs+ eae+ Mp+) were present in E. coli from healthy and diarrheic calves corresponding to O5:H-, O5:H27, O20:H?, O26:H11, O38:H?, O103:H-, O103:H2, O111:H-, O118:H16, O165:H-serotypes. The presence of the eae gene was significantly more frequent among VTEC strains isolated from calves (20/26; 76%) than from adult cattle (1/39; 2.5%) (p < 0.005). VT2+ eae- E. coli was prevalent in foods and adult cattle at slaughterhouse. The prevalence of the eae gene was similar between VTEC strains isolated from meat (0/21) and adult cattle (1/39; 2.5%) which constitutes the main population processed at slaughterhouses in Argentina. Serotyping showed that VTEC strains were distributed among 31 serotypes, some of which (O20:H19, O91:H21, O113:H21, O116:H21, O117:H7, O171:H2, OX3:H21) were shared between bovine and food strains. These O serogroups have been isolated from cases of haemorrhagic colitis (HC) and haemolyticuraemic syndrome (HUS) in humans in several continental European countries. This study confirms the role of cattle as a reservoir of many VTEC serotypes other than O157:H7 and represents a base for future diagnostic, prevention and control strategies of EHEC in this country. In addition, this study affirms the advantages of PCR-based screening of E. coli isolates given the finding of so many verotoxin-producing strains.

Effects of interaction between Escherichia coli verotoxin and lipopolysaccharide on cytokine induction and lethality in mice

In Escherichia coli 0157 infections, verotoxins (VT) play a critical role in causing the disease, although other factors such as lipopolysaccharide (LPS) and inflammatory cytokines may affect the progression and course of the disease. The present study examined the roles of VT and LPS in induction of serum cytokines and lethality in mice. LD50 of VT2 (13 ng) was c. 10(4)-fold smaller than that of LPS (400 microg). Although the lethal toxicity of these toxins was examined in several experimental conditions, such as VT2 (5, 10, 20, 40 ng/mouse) alone or in combination with LPS (100 microg/mouse) at various times (-2 days to +2 days), no evidence of synergy was observed. VT2 did not augment LPS-induced tumour necrosis factor-alpha (TNF-alpha) or interleukin-6 production, and conversely suppressed TNF-alpha production when it was injected 2 days before LPS challenge. The data failed to indicate either synergic or additive effects of VT and LPS on cytokine production or lethality in mice. In contrast, antagonistic interactions were clearly observed in cytokine production in certain conditions. The results suggested that these toxins may be co-operatively involvedin the pathology of VT-related diseases, but not through synergic interactions.

Disorders in the immune responses of T- and B-cells in mice administered intravenous verotoxin 2

To obtain a better insight into the pathogenesis of verotoxin-producing Escherichia coli (VTEC)-associated diseases, we explored the effect of verotoxin 2 (VT2) on the immune response in mice. The distribution of lymphocyte phenotypes and the lymphocyte immune response were examined after intravenous administration of VT2 to mice. Among the peripheral lymphocytes and splenocytes of 4-week-old C57BL/6 mice, there was first of all a decrease in T-cells, which began 24 h after intravenous administration of VT2 (50 ng/kg, lethal dose). The CD4+ cell subpopulations of the peripheral blood and spleen were significantly decreased at 24 h, while the B220+ splenocyte subpopulation was markedly decreased at 45 h after VT2 administration. In the thymus, a decrease in CD4+CD8+ cells was predominantly observed near death. Interestingly, in E. coli lipopolysaccharide (LPS)-responder mouse strains (C57BL/6 and C3H/HeN) cotreated with LPS, the susceptibility to VT2 was enhanced, and the increase in B220+ cells induced by LPS alone was suppressed. Furthermore, splenocytes from C57BL/6 mice treated with VT2 (50 ng/kg) 6-24 h earlier reduced LPS-induced proliferative responses to 50-52% of that in control cells, indicating that the effect of VT2 on the immunoresponse seen in vivo may be negatively exerted on the proliferation of the cells. In addition, the number of splenocytes that produced anti-sheep red blood cell antibody was decreased in mice treated with VT2. These results suggest that VTEC infection may eliminate CD4+ and CD8+ T-cells and B-cells by affecting their survival and proliferative responses, leading to reduced antibody production.

Application of polymer-embedded proteins to fabrication of DNA array

A plasma-polymerized film (PPF) of hexamethyldisiloxane [HMDS; (CH(3))(3)SiOSi(CH(3))(3)] was used to immobilize streptavidin on a glass substrate. Another layer of HMDS-PPF was also applied to the protein, which was first adsorbed to an underlayer of the same kind of film. As the result, the streptavidin was "embedded" between the two layers of HMDS, whereby biotinylated molecules could be efficiently captured. The second layer of approximately 30 to 45 A PPF was sufficient to allow the binding of biotinylated molecules, whereas thicknesses of >90 A significantly hindered the streptavidin-biotin interactions. Fluorescence analysis revealed that the absence of an HMDS plasma-polymer (HMDS-PP) layer on either side of the streptavidin film resulted in a decrease in biotin binding. This immobilization technique was used to bind biotinylated oligonucleotides in sequence-specific DNA-DNA interactions. The hydrophobic properties of the plasma-polymerized HMDS thin film acted to minimize nonspecific DNA binding to the glass substrate. A DNA array was fabricated using this procedure and showed greatly decreased nonspecific DNA binding compared with a poly-L-lysine coated substrate.

Bcl-2 antiapoptotic protein mediates verotoxin II-induced cell death: possible association between bcl-2 and tissue failure by E. coli O157:H7

Verotoxin II (VTII: or Shiga-like toxin 2) is a key factor for Escherichia coli O157:H7-induced multiple tissue failure and contains a pentameric sequence (NWGRI) similar to the Bcl-2 homolog domain, BH1. In the current study, we demonstrate that VTII, but not VTI, interacts with Bcl-2 through each BH1 domain pentameric sequence (NWGRI) and that the VTII/Bcl-2 complex is necessary for cell-death induction in target cells. VTII translocates to mitochondria and induces cell death only when target cells are expressing Bcl-2. In addition, interruption of VTII-Bcl-2 complex formation by a pentameric BH1 synthetic peptide suppresses VTII-induced cell death. In the present article, we propose that Bcl-2 mediates VTII-induced target cell death by the interaction with each pentameric sequence of BH1 domain.

Rapid SLT gene detection on polyethylene-coacrylic acid film without molecular labels or surface-fouling agents

The commercially available copolymer of 10 mol% acrylic acid and polyethylene is easily formed into a nonfluorescing, non-polynucleotide-adsorbing film. The film has surface carboxylate functions whose concentration can be increased by heating to 80 degrees C in 30% NaOH. The carboxylate groups will react at pH approximately 7 with commercially available, oligo-DNA, 2-8 ng/microl, that has been synthesized with a C(12)-alkylamino tail on the 5'-end. The reaction is mediated with water-soluble carbodiimide reagent and is assumed to result in a primary amide bond between the polymer film and the modified oligo-DNA. The tethered oligo-DNA retains its hybridization activity, and its surface concentration is sufficient to permit qualitative, labelless detection of hybridized target by fluorescence after brief staining with ethidium bromide. The film is used to detect Shiga-like toxin gene II (SLT-II) from Escherichia coli O157:H7 after asymmetric, capillary, PCR amplification, and a 4-h hybridization. Captured target may be removed from the film using distilled water, after which the film can be used again without noticeable loss of activity. The method provides relatively rapid detection of PCR amplimers without having to use molecular labels, or surface-fouling agents.

Macrolides and clindamycin suppress the release of Shiga-like toxins from Escherichia coli O157:H7 in vitro

We investigated the effects of antimicrobial agents fosfomycin (FOS), cefdinir (CDIN), levofloxacin (LEVX), rokitamycin (ROK), roxithromycin (ROX), and clindamycin (CLI) on the release of Shiga-like toxins (SLTs) by enterohaemorrhagic Escherichia coli (EHEC). EHEC was cultured for 14 h in the presence of ROX, ROK or CLI at sub-minimum inhibitory concentrations (subMICs) of 1.56-6.25 mg/l, followed by assay of the level of SLTs in the supernatants using cytotoxicity assay and reversed passive latex agglutination method. Exposure to ROX, ROK or CLI reduced the amount of released SLTs compared with untreated control cultures (P<0.05). These agents however, did not decrease the number of viable EHEC, indicating the importance of bactericidal agents. When the bacteria was exposed to CDIN, FOS or LEVX, the level of SLTs in the culture supernatant increased with the destruction of bacterial cells in the order of CDIN, FOS, LEVX. When 0.5 mg/l of LEVX was added to cultures with or without pretreatment using ROX, ROK, or CLI, the release of SLTs was reduced by this pretreatment (P<0.05). These results may have clinical implications for the treatment of EHEC infection.

A mutant Shiga-like toxin IIe bound to its receptor Gb(3): structure of a group II Shiga-like toxin with altered binding specificity

BACKGROUND

Shiga-like toxins (SLTs) are produced by the pathogenic strains of Escherichia coli that cause hemorrhagic colitis and hemolytic uremic syndrome. These diseases in humans are generally associated with group II family members (SLT-II and SLT-IIc), whereas SLT-IIe (pig edema toxin) is central to edema disease of swine. The pentameric B-subunit component of the majority of family members binds to the cell-surface glycolipid globotriaosyl ceramide (Gb(3)), but globotetraosyl ceramide (Gb(4)) is the preferred receptor for SLT-IIe. A double-mutant of the SLT-IIe B subunit that reverses two sequence differences from SLT-II (GT3; Gln65-->Glu, Lys67-->Gln, SLT-I numbering) has been shown to bind more strongly to Gb(3) than to Gb(4).

RESULTS

To understand the molecular basis of receptor binding and specificity, we have determined the structure of the GT3 mutant B pentamer, both in complex with a Gb(3) analogue (2.0 A resolution; R = 0.155, R(free) = 0.194) and in its native form (2.35 A resolution; R = 0.187, R(free) = 0.232).

CONCLUSIONS

These are the first structures of a member of the medically important group II Shiga-like toxins to be reported. The structures confirm the previous observation of multiple binding sites on each SLT monomer, although binding site 3 is not occupied in the GT3 structure. Analysis of the binding properties of mutants suggests that site 3 is a secondary Gb(4)-binding site. The two mutated residues are located appropriately to interact with the extra betaGalNAc residue on Gb(4). Differences in the binding sites provide a molecular basis for understanding the tissue specificities and pathogenic mechanisms of members of the SLT family.

Development and evaluation of a PCR-microplate capture hybridization method for direct detection of verotoxigenic Escherichia coli strains in artificially contaminated food samples

For the purpose of detecting, directly in food, verotoxigenic Escherichia coli, a microplate hybridization method for the detection of PCR products from the SLT I and SLT II genes, was developed and evaluated. Two pairs of primers and two probes, specific for the SLT I gene and for the SLT II gene, were designed and tested. For the strains containing both genes, two PCR products of different molecular weights were obtained, whereas when only one gene was present only one fragment resulted from PCR. The use of the biotin-labeled probes allowed the immobilization of the PCR products in the microtiter plate wells and by this means their detection was possible using an ELISA-based technique. Forty artificially contaminated and fifty naturally contaminated food samples were analyzed by using the PCR-microplate hybridization technique developed in this study. All the artificially contaminated food samples were positive, independently of the number of cells inoculated before the enrichment step, whereas the naturally contaminated food samples were all negative.

Detection of Escherichia coli O157:H7 in heifers' faecal samples using an automated immunoconcentration system

Pre-treatment of a 5-h enrichment culture with an automated immunoconcentration (ICE) system greatly improved the isolation of Escherichia coli O157:H7 from spiked heifer faecal samples. Enrichment samples plated directly onto sorbitol MacConkey agar (SMAC) and SMAC agar supplemented with cefixime and potassium tellurite (CT-SMAC) showed recovery rates of 8% and 56%, respectively. However, after ICE treatment, E. coli O157:H7 was recovered from 92% of the samples on SMAC and 100% on CT-SMAC. Immunoconcentration analysis of heifers' faecal samples collected from a slaughter-house in France, during March to June 1998, showed that 1% (three of 300) was positive for E. coli O157:H7. Phenotypic and genotypic analysis showed that all three isolates carried both the O157 and H7 antigens, did not ferment sorbitol or had beta-glucuronidase activity and carried trait virulence factors for E. coli O157:H7 (uidA allele, eaeA and pO157 plasmid). However, only one strain was toxigenic and this strain produced a single toxin, namely verotoxin 2.

Chromosome of the enterohemorrhagic Escherichia coli O157:H7; comparative analysis with K-12 MG1655 revealed the acquisition of a large amount of foreign DNAs

A complete Xba I and Bln I cleavage map was constructed for the chromosome of an enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain isolated from an outbreak in Sakai City, Japan, in 1996. A comparative chromosome analysis with E. coli K-12 strain MG1655 was made. The EHEC chromosome was approximately 5600 kb in length, 1 Mb larger than that of MG1655. Despite the marked difference in chromosome length, the location and direction of seven rRNA operons of the EHEC strain were similar to those for MG1655. Overall organization of genes common in both strains is also highly conserved. Chromosome expansion was observed throughout the EHEC chromosome, albeit in an uneven manner. A large portion of the chromosome enlargement was observed in the region surrounding the replication terminus, particularly in a segment containing the terA locus. Sample sequencing of 3627 random shotgun clones suggested the presence of approximately 1550 kb strain-specific DNAs on the EHEC chromosome, most of which are likely to be of foreign origin.

Inhibition of neutrophil apoptosis by verotoxin 2 derived from Escherichia coli O157:H7

In order to evaluate the pathological role of verotoxin 2 (VT2), we investigated the effects of VT2 on neutrophil apoptosis in vitro. The results showed that VT2 caused a significant delay in spontaneous neutrophil apoptosis and that the effect was abrogated by a protein kinase C inhibitor. These data indicate that longer survival of neutrophils may aggravate neutrophil-mediated tissue damage in VT2-associated diseases.

Chemotherapy for enterohemorrhagic Escherichia coli O157:H infection in a mouse model

The aim of this study is to evaluate the therapeutic effect of the antimicrobial agents, fosfomycin (FOM), minocycline (MINO), kanamycin (KM) and norfloxacin (NFLX) in the enterohemorrhagic Escherichia coli (EHEC) infected mouse model which we established previously (Infect. Immun. 62 (1994) 3447-3453). Each of the antimicrobial agents, 1/16 LD(50), was given to the mice per os (p.o. ) or intraperitoneally (i.p.) for 3 days after bacterial inoculation and then we observed their mortality rate for 2 weeks. The mortality rates of mice administered with MINO (p.o./i.p.), KM (p.o.), NFLX (p. o./i.p.) were significantly lower than those of the control group. Both the bacterial number and VT2c level in the feces of the FOM group were lower than those of the NFLX group on day 1, but reversed on day 3. In an in vitro experiment, each of the four drugs in combination with mitomycin C (MMC) caused a more significant decrease in the bacterial number than sole MMC, and they consequently indicated the suppressive effect on the release of VT2c.

Complete nucleotide sequence of the prophage VT2-Sakai carrying the verotoxin 2 genes of the enterohemorrhagic Escherichia coli O157:H7 derived from the Sakai outbreak

The enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain RIMD 0509952, derived from an outbreak in Sakai city, Japan, in 1996, produces two kinds of verotoxins, VT1 and VT2, encoded by the stx1 and stx2 genes. In the EHEC strains, as well as in other VT-producing E. coli strains, the toxins are encoded by lysogenic bacteriophages. The EHEC O157:H7 strain RIMD 0509952 did not produce plaque-forming phage particles upon inducing treatments. We have determined the complete nucleotide sequence of a prophage, VT2-Sakai, carrying the stx2A and stx2B genes on the chromosome, and presumed the putative functions of the encoded proteins and the cis-acting DNA elements based on sequence homology data. To our surprise, the sequences in the regions of VT2-Sakai corresponding to the early gene regulators and replication proteins, and the DNA sequences recognized by the regulators share very limited homology to those of the VT2-encoding 933W phage carried by the EHEC O157:H7 strain EDL933 reported by Plunkett et al. (J. Bacteriol., p1767-1778, 181, 1999), although the sequences corresponding to the structural components are almost identical. These data suggest that these two phages were derived from a common ancestral phage and that either or both of them underwent multiple genetic rearrangements. An IS629 insertion was found downstream of the stx2B gene and upstream of the lysis gene S, and this might be responsible for the absence of plaque-forming activity in the lysate obtained after inducing treatments.

[Colibacillosis in swine: proof of vaccine efficacy]

The damage caused in the economy and animal sanity by the porcine colibacilosis are significant and they deserve the investigation of preventive measures that give answers to the producers. Existing at the present time approximately 21,000 pigs in Corrientes and 110,000 in Chaco provinces of Argentine, the losses for diarrhea that exterminate whole litters, acquire relevance, specially if they can be prevented or cured. For that reason, having 21 strains of enteropathogenic and verocitotoxigenic E. coli (ETEC/VTEC) isolated from pigs of the North East of Argentine, that were recognized by PCR, two were selected, containing the genes for STIa, STIb, LTI, VT2e (SLT-IIv) and F4 (K88). They were spread on nutrient agar and Minca medium, to obtain the suspension in PBS, which was inactivated with formol. After the sterility and innocuity controls, it was diluted to a 12 x 10(8) concentration to make the mouse protection test in 20 mice, of 18-20 g, inoculating the vaccine the days 1, 4, 7 and 10, by the intraperitoneal route, doses of 0.25 ml each one. The day 21 after beginning the test the animals were challenged with 50 LD50, and a protection of 85% was obtained. To determine the LD50, we prepared a suspension in physiologic solution, corresponding to Mac Farland's tube No 10, making dilutions from 10(-1) to 10(-5) and applying the statistical method of Reed and Muench. These first results encourage us to continue working after a prophylactic measure that were effective, potent and elaborated with strains of this area.

Molecular characterisation of verocytotoxin-producing Escherichia coli of serogroup O111 from different countries

A collection of epidemiologically unrelated verocytotoxin (VT)-producing Escherichia coli (VTEC) strains of serogroup O111 isolated from human patients and cattle with diarrhoeal disease in five different countries were characterised by determination of their VT genotypes, the presence of other virulence factors such as the intimin-coding eae gene and the enterohaemorrhagic E. coli (EHEC) plasmid, and their antibiotic susceptibility patterns. The genetic relatedness among isolates was evaluated by genomic DNA fingerprinting techniques such as restriction fragment length polymorphism analysis of ribosomal RNA genes (ribotyping) and pulsed-field gel electrophoresis. The results indicated that the VTEC O111 examined belong to two distinct clonal lineages. The first group was constituted mainly of non-motile, eae-positive, EHEC plasmid-positive isolates from both man and cattle. The second lineage was represented by an O111:H2 epidemic strain, isolated during an outbreak of haemolytic uraemic syndrome in France and exhibiting an unusual combination of virulence factors: VT production and aggregative adhesion to HEp-2 cells associated with an enteroaggregative E. coli (EAEC) plasmid.

A reverse-sandwich enzyme-linked immunosorbent assay for verocytotoxin 1 and 2 antibodies in human and bovine sera

A reverse-sandwich enzyme-linked immunosorbent assay (ELISA), in which an antibody is sandwiched by antigens, was established for the titration of antibodies to verocytotoxins (VT) in human and animal sera. This assay has two advantages over a conventional indirect ELISA: (i) higher specificity and sensitivity and (ii) the ability to comparably titrate antibodies from different species. The VT1 (Shiga-like toxin 1) antibody-positive rates were 5% in 202 normal adult humans and 99% in 93 normal cattle at a dairy farm. This ELISA is most suitable for seroepidemiologic studies of infections with VT-producing Escherichia coli in humans and various animal species.

Synthesis of an artificial glycoconjugate polymer carrying Pk-antigenic trisaccharide and its potent neutralization activity against Shiga-like toxin

Fluorescence-labeled glycoconjugate polymers carrying carbohydrate segments of a globotriaosyl ceramide (Gb3) were synthesized and subjected to biological assays using Escherichia coli O-157 strains and Shiga-like toxins (Stx-I and Stx-II). For the fluorescence labeling, a new polymerizable fluorescent monomer with a TBMB carbonyl chromophore (Ex. 325 nm, Em. 410 nm) was designed. A glycosyl monomer of the trisaccharide segment of Gb3 was prepared from p-nitrophenyl beta-lactoside and copolymerized with acrylamide and the fluorescent monomer to prepare a fluorescence-labeled glycoconjugate copolymer carrying [alpha-D-galactopyranosyl-(1-->4)-beta-D-galactopyranosyl]-(1-->4)-beta- D-glucopyranoside. The polymer showed potent neutralization activity against Stx-I and also binding activity onto E. coli O-157 strains.

Prevalence of virulence factors of Escherichia coli strains isolated from diarrheic and healthy piglets after weaning

This study determined the prevalence of F4, F5, F6, F17 and F41 fimbriae and the genes for FedA (F18 fimbriae), LT and ST enterotoxins, and Shiga toxins Stx1, Stx2 and Stx2e among E. coli isolated from 372 weaned pigs with diarrhea and 46 healthy pigs of the same age. Agglutination tests showed that most isolates were negative for all five fimbrial antigens. The F4 antigen was found in 71 (19.1%) and the F5, F6, or F41 antigen was detected in 6.4% of isolates from diseased pigs. Genes for the F18 fimbriae were detected in 10 (2.7%) strains from diarrheic pigs and in 1 of 46 isolates from healthy pigs. Most isolates (213, 57.3%) from pigs with diarrhea were positive for LTI only or for LTI and STI or Stx2e toxin genes. Fifteen strains (13.7%) possessed only the STI or STII toxin genes. All F4-positive bacteria had genes for LTI or LTI and STI, whereas F18-positive isolates had genes for LTI, LTI/STI, or LTI/Stx2e. Of the strains isolated from diseased pigs, 264 (71.0%) were negative for the fimbrial antigens (genes) examined in this study. The fimbria-negative isolates frequently possessed genetic determinants for LTI (118, 31.7%) or for STII (16, 4.3%) enterotoxins.

Haemolytic-uraemic syndrome caused by vero toxin-producing Escherichia coli serotype Rough: K-: H49

The first case of haemolytic-uraemic syndrome (HUS) caused by Vero toxin-producing Escherichia coli (VTEC) which belonged to a novel serotype, Rough: K-: H49, is reported. The case was initially diagnosed as nephropathia epidemica caused by Puumala virus, but the subsequent diagnosis of HUS caused by VTEC was made after bacteriological investigation. The strain isolated fermented sorbitol produced VT2 toxin but not enterohaemolysin, nor did it carry the eaeA gene. In VTEC strains, the O antigen, the eaeA gene and enterohaemolysin production have been characterized as virulence-associated factors and believed to have an effect on pathogenesis of these strains to cause haemorrhagic colitis or HUS. The findings of this study demonstrate that there is a need for further studies to evaluate the pathogenetic mechanism of VTEC and need for easy diagnostic methods exploiting other properties than O157 antigen and non-fermentation of sorbitol to find all VTEC in human infections.

In vitro assessment of a chemically synthesized Shiga toxin receptor analog attached to chromosorb P (Synsorb Pk) as a specific absorbing agent of Shiga toxin 1 and 2

A synthetic analog of Shiga toxin (Stx) receptor (Synsorb Pk) was quantitatively assessed to determine whether it can protect human renal adenocarcinoma cells (ACHN cells) from the cytotoxicity of Stx1 and Stx2 by coincubation experiments. Coincubation of 100 and 20 ng of Stxl and Stx2 with 50 mg of Synsorb Pk for 1 hr at 37 C in 1 ml of Eagle's Minimum Essential Medium supplemented with 1% (v/v) non-essential amino acid and 10% (v/v) fetal calf serum protected 50% of the cells from the cytotoxic effect. Chromosorb P, an inert matrix control, did not absorb the Stxs at all. Heat-treatment (boiled for 10 min) to Synsorb Pk caused a 50% decrease in Stx2-binding activity, but did not effect the Stx1 binding. Further, Stxs bound to Synsorb Pk could be demonstrated. When 20 mg of Synsorb Pk was coincubated for 30 min at 37 C in 1 ml of phosphate-buffered saline with 1 and 10 ng or more of Stx1 or Stx2, respectively, the toxins could be detected on the surface when the bound toxins on Synsorb Pk were used as the solid phase in enzyme immunoassay. The amount of 100 ng/ml of both Stxl and Stx2 appeared to saturate 20 mg/ml of Synsorb Pk after coincubating for 30 min at 37 C. While assessing the Stxs' binding activity to Synsorb Pk, it was demonstrated that Stxl had a higher affinity to Pk trisaccharide than Stx2. These observations provide useful information on the effectiveness of Synsorb Pk to trap and eliminate free Stxs produced in the gut of patients infected by Stx-producing Escherichia coli, and to prevent the progression of hemorrhagic colitis to hemolytic uremic syndrome.