[The study for the immuno-protection of E. coli O157:H7 outer membrane protein]

OBJECTIVE

To evaluate the protective efficacy against a lethal dose of E. coli O157:H7 after intranasal, oral and subcutaneous immunization with the outer membrane protein (OMP) extracted from the whole cell of E. coli O157:H7.

METHODS

Female BALB/C mice were immunized three times (on days 0, 7 and 14) with OMP and CT or Complete Frund adjuvant. On the 21st day after the last immunization, serum, fecal extracts and vaginal washes were collected for the detection of antigen-specific antibody responses by ELISA before the oral challenge with E. coli O157:H7 933. And the antigens that induced the specific antibody responses were analysed by Western-blotting. Then, the mice were orally challenged with 0.3 ml 4.25 x 10(10)/ml live E. coli O157:H7, and the mortality was recorded. On the 7th day after the challenge, the mice were sacrificed and the heart, liver, lung, kidney, small intestine and colon were collected. Then the histology lesions were observed by light microscopy.

RESULTS

In ELISA, both intranasal and oral immunization, with CT as a mucosal adjuvant, induced strong anti-OMP IgA responses in serum, fecal extract and vaginal washes, and anti-OMP IgG responses in serum. However, the intranasal immunization was much more effective to induce specific IgA and IgG responses than the oral immunization. In contrast to mucosal immunization, subcutaneous immunization only induced high levels of specific IgG antibodies in serum, and did not effectively promote IgA immune response. The results of the protective efficacy after challenge showed that both intranasal and oral immunizations with OMP provided significant protection (86.7% to 40%, P < 0.01 and 73.3% to 40%, P < 0.05) against a lethal dose of E. coli O157:H7 challenge, and intranasal immunization possessed a better protective ability (86.7% to 73.3%, P < 0.05). In contrast, the mice immunized subcutaneously were not protected. They were died more early after oral challenge. Furthermore, the histopathological features of the kidney, colon and other organs also appeared to be well correlated with immunization route. In comparison with the mice immunized subcutaneously and those in control group, the severity of the histopathological lesions in the tissues of the mice immunized intranasally was minimal.

CONCLUSION

These results suggested that the intranasal immunization should be the best choice of vaccine development against E. coli O157:H7.

Development of procedures for rapid detection of E. coli O157:H7 from source and finished water samples

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7, the causative agent for haemolytic uraemic syndrome, has become a significant health concern, due to an increasing number of cases. The focus of this project was rapid (<8 h) detection of E. coli O157:H7 from source and finished waters samples, either directly or indirectly, by dovetailing the procedures with existing total coliform procedures. Evaluation of four immunological lateral diffusion assays determined a detection range between 1 x 10(4) and 1 x 10(6) CFU, with the Reveal E. coli O157:H7 Test System (Neogen) being the most sensitive for detecting E. coli O157:H7. Evaluation of the BAX System for molecular detection determined that as few as 10 CFU could be reproducibly detected. Coupling either of these detection procedures with organism propagation using Tryptic Soy Broth (TSB) enabled sufficient quantities of E. coli O157:H7, such that the Reveal and BAX detection methods could be used with the 8 h time frame. Examination of matrix effects on the overall procedure indicated little impact on method performance.

Passive Transfer on Antibodies to Shiga Toxin-Producing Escherichia coli O26, O111 and O157 Antigens in Neonatal Calves by Feeding Colostrum

To study whether or not passive immunity of neonatal calves against Shiga toxin-producing Escherichia coli (STEC) O26, O111, and O157 was obtained by colostrum administration, serum antibodies in calves after the feeding were determined by enzyme-linked immunosorbent assay (ELISA) in comparison with antibodies in colostrum and sera from donor dams. The highest antibody titers to STEC in colostrum from dams were detected soon after parturition. The antibody titers were found to be elevated in sera of neonatal calves (4-9 hr after birth) orally administered with colostrum with high antibody titers, suggesting that passive immunity of neonatal calves to STEC infection may be obtained by feeding colostrum. These results suggest that colostrum administration to neonatal calves may play an important role in elevating serum antibodies against STEC in neonatal calves.

A self-assembled monolayer-based piezoelectric immunosensor for rapid detection of Escherichia coli O157:H7

A piezoelectric immunosensor was developed for rapid detection of Escherichia coli O157:H7. It was based on the immobilization of affinity-purified antibodies onto a monolayer of 16-mercaptohexadecanoic acid (MHDA), a long-chain carboxylic acid-terminating alkanethiol, self-assembled on an AT-cut quartz crystal's Au electrode surface with N-hydroxysuccinimide (NHS) ester as a reactive intermediate. The binding of target bacteria onto the immobilized antibodies decreased the sensor's resonant frequency, and the frequency shift was correlated to the bacterial concentration. The stepwise assembly of the immunosensor was characterized by means of both quartz crystal microbalance (QCM) and cyclic voltammetry techniques. Three analytical procedures, namely immersion, dip-and-dry and flow-through methods, were investigated. The immunosensor could detect the target bacteria in a range of 10(3)-10(8)CFU/ml within 30-50 min, and the sensor-to-sensor reproducibility obtained at 10(3) and 10(5) colony-forming units (CFU)/ml was 18 and 11% R.S.D., respectively. The proposed sensor was comparable to Protein A-based piezoelectric immunosensor in terms of the amount of immobilized antibodies and detection sensitivity.

Plant cell-based intimin vaccine given orally to mice primed with intimin reduces time of Escherichia coli O157:H7 shedding in feces

Intimin is the primary adhesin of Escherichia coli O157:H7, the most common infectious cause of bloody diarrhea in the United States and the leading cause of acute kidney failure in children who develop hemolytic uremic syndrome. Cattle are the primary reservoir of E. coli O157:H7. Indeed, most cases of E. coli O157:H7 infection in the United States occur after ingestion of contaminated undercooked hamburger or produce that had contact with bovine manure. Because intimin is required for persistent colonization of neonatal calves and adult cattle, we hypothesized that an intimin-based vaccination strategy in calves would reduce colonization of cattle with E. coli O157:H7. To test this concept in a small-animal model, we developed transgenic tobacco plant cells that express the carboxy-terminal host cell-binding domain of E. coli O157:H7 intimin. Mice were either immunized intraperitoneally with intimin expressed from the plant cells, fed transgenic plant cells, or both. Here we show that these mice generated an intimin-specific mucosal immune response when primed parenterally and then boosted orally and also exhibited a reduced duration of E. coli O157:H7 fecal shedding after challenge.

Critical roles for stx2, eae, and tir in enterohemorrhagic Escherichia coli-induced diarrhea and intestinal inflammation in infant rabbits

Enterohemorrhagic Escherichia coli (EHEC) is a group of food-borne pathogens that can cause diarrhea, colitis, and the hemolytic uremic syndrome (HUS). The importance of several of the proposed EHEC virulence factors lacks experimental verification in animal models. The limitations of current animal models led us to reexamine the infant rabbit model for the study of EHEC pathogenicity. Here, we report that intragastric inoculation of a Shiga toxin 2 (Stx2)-producing E. coli O157:H7 clinical isolate into infant rabbits led to severe diarrhea and intestinal inflammation but no signs of HUS. We constructed a set of isogenic derivatives of this isolate with deletions in several putative virulence genes, including stx(2), eae, tir, and ehxA, to investigate the contribution of individual virulence factors to EHEC pathogenicity. stx(2) increased the severity and duration of EHEC-induced diarrhea. Furthermore, although stx(2) had no role in EHEC intestinal colonization nor was it required for EHEC-induced inflammation, stx(2) altered how the host responded to EHEC infection by promoting heterophilic infiltration of the colonic epithelium and lamina propria. Intragastric inoculation of purified Stx2 also induced inflammation and diarrhea in this model. Diarrhea and intestinal inflammation were also dependent on EHEC colonization, as EHEC derivatives with deletions in eae and tir did not colonize, form attaching and effacing lesions, or develop clinical signs of disease. Our studies indicate that infant rabbits are a useful model for investigation of the intestinal stage of EHEC pathogenesis and suggest that Shiga toxin may play a critical role in causing diarrhea and inflammation in patients infected with EHEC.

[Studies on the polyclonal antibody and the double-antibody enzyme-linked immunosorbent assay against E. coli O157 in food]

The polyclonal antibody (PcAb) for E. coli O157:H7 was available by intravenous injection with New Zealand rabbit with E. coli O157:H7 ATCC43895 strain. Together with the monoclonal antibody (McAb) 3A5 specific against E. coli O157 and O113:H21, a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed with the as the capture antibody and the McAb 3A5 as the detection antibody. The detection limits are 10(3)-10(4) cfu/ml in pure culture of E. coli O157 and without any cross reaction with the non-O157 strains. With 10 h enrichment procedure, E. coli O157:H7 recovered well from inoculated ground poultry meat and pasteurized milk at levels of 0.1 cfu/g(cfu/ml). The results demonstrated that the double-antibody sandwich ELISA is a sensitive and specific method for detecting E. coli O157 in food samples.

Antibody responses to Escherichia coli O157 and other lipopolysaccharides in healthy children and adults

In Mexico, diarrheal disease due to different serotypes of Escherichia coli is highly prevalent, with only sporadic isolation of O157 non-H7 strains. This could be due to exposure to the O157 or related E. coli lipopolysaccharide (LPS), such as O7 or O116, at an early age. By using enzyme-linked immunosorbent assay (ELISA) and Western blotting, the present study analyzed 605 serum samples from Mexican adults and infants without clinical symptoms of disease for the presence of antibodies to these three E. coli LPSs. The bactericidal activities of homologous and heterologous rabbit and human serum samples against O7, O116, and O157 E. coli LPSs were also determined. By using a cutoff point of 0.7, it was found by the ELISAs that 28 of 562 (5%) of the serum samples from adolescents and adults and 2 of 43 (5%) of the serum samples from infants less than 1 year of age reacted with the O157 LPS. By using cutoff points between 0.4 and 0.699, the proportion of serum samples from both age groups that reacted with the O157 LPS increased to 20%. Western blotting analysis of selected serum samples that showed an intermediate response against the O157 LPS by the ELISAs showed that 61 of 88 (69%) reacted with the same LPS. A similar result was observed for maternal milk samples. The bactericidal activities of rabbit serum samples against the O7, O116, and O157 LPSs showed that they were positive for both homologous and heterologous antigens. Similar results were observed with the human serum samples. O157 non-H7 strains were identified in only 10% of the E. coli strains isolated from 263 Mexican children with and without diarrhea over the past 15 years. This absence of O157:H7 strains in Mexico may be associated with the presence of antibodies against O157 or related E. coli LPSs.

Procedures for PreparingEscherichiacoliO157:H7 Immunoliposome and Its Application in Liposome Immunoassay

Although Escherichia coli serotype O157:H7 was identified as a human pathogen in the ninth decade of the twentieth century, it has become recognized as a major foodborne pathogen. In the United States, the severity of E. coli O157:H7 infection in the young and the elderly has had a tremendous impact on human health, the food industry, and federal regulations regarding food safety. In laboratory diagnosis, most microbiologic assays rely on a single phenotype to selectively isolate this pathogen. However, the process is labor- and time-consuming. It is important eventually to develop new assay procedures to detect them. Immunoliposomes, anti-E. coli O157:H7 antibody-tagged liposomes, encapsulating a visible dye, sulforhodamine B, were used in the present study for the development of a field-portable colorimetric immunoassay to detect E. coli O157:H7. The N-succinimidyl-S-acetylthioacetate derivative of the antibodies (anti-E. coli O157: H7) was first conjugated through the reactive N-(kappa-maleimidoundecanoyloxy) sulfosuccinimide ester derivative of dipalmitoylphosphatidylethanolamine and subsequently incorported into liposomes to form the immunoliposomes. A plastic-backed nitrocellulose strip with two immobilized zones is the basis for a sandwich assay to detect E. coli O157:H7. The first zone is the antigen capture zone (AC zone), which is used in a sandwich (noncompetitive) assay format; the other is the biotin capture zone (BC zone), which is used as a positive control for the strip. During the capillary migration of the wicking reagent containing 50 microL of immunoliposomes and 90 microL of the test sample, E. coli O157:H7 with surface-bound immunoliposomes is captured at the AC zone, while the unbound immunoliposomes migrate and bind to the antibiotin antibodies coated on BC zone. The color density of the AC zone were directly proportional to the amount of E. coli O157:H7 in the test sample. The detection limit of the current assay with heat-killed E. coli O157:H7 was approximately 2500 cells. The selectivity of the newly developed biosensor system was investigated, and pathogens, including Salmonella typhimurium and Listeria genus specific, were proven to have no interference with the detection of E. coli O157:H7.

A B cell-based sensor for rapid identification of pathogens

We report the use of genetically engineered cells in a pathogen identification sensor. This sensor uses B lymphocytes that have been engineered to emit light within seconds of exposure to specific bacteria and viruses. We demonstrated rapid screening of relevant samples and identification of a variety of pathogens at very low levels. Because of its speed, sensitivity, and specificity, this pathogen identification technology could prove useful for medical diagnostics, biowarfare defense, food- and water-quality monitoring, and other applications.

Analysis of saliva for antibodies to the LPS of Escherichia coli O157 in patients with serum antibodies to E. coli O157 LPS

The salivary antibody response to the Escherichia coli O157 LPS antigen was assessed in 44 patients with serum antibodies binding to the LPS of E. coli O157. Saliva from 477 controls was also examined to assess the specificity of the immunoassay used. Twenty of the 44 patients had salivary antibodies to E. coli O157 LPS, giving the salivary antibody test a sensitivity of 0.45 and a predictive positive value for seropositivity of 1.00. The presence of these antibodies appeared not to relate to the time interval between serum sampling and saliva sampling. None of the 477 volunteers had salivary antibodies binding to the LPS of E. coli O157 alone; however, 15 had antibodies which bound non-specifically to both O157 LPS and BSA.

Protection against Shiga toxin 1 challenge by immunization of mice with purified mutant Shiga toxin 1

Shiga toxin 1 (Stx1) of enterohemorrhagic Escherichia coli O157:H7 was cloned, and four mutant Stx1s were constructed by site-directed mutagenesis with PCR. The wild-type and mutant Stx1s with amino acid replacements at positions 167 and 170 of the A subunit were purified by one-step affinity chromatography with commercially available Globotriose Fractogel, and the mutant Stxs were used for the immunization of mice. The mutant toxins were nontoxic to Vero cells in vitro and to mice in vivo and induced the immunoglobulin G antibody against the wild-type Stx1, which neutralized the cytotoxicity of Stx1. The induced antibody titers depended on the mutation at position 170 of the A subunit. The mice immunized with the mutant Stx1s were protected against a challenge of approximately 100 times the 50% lethal dose of the wild-type Stx1, suggesting that the mutant toxins are good candidates for toxoid vaccines for infection by Stx1-producing E. coli.

Diarrhea incidence and farm-related risk factors for Escherichia coli O157:H7 and Campylobacter jejuni antibodies among rural children

Serum samples were obtained from 215 farm-resident children and 396 non-farm-resident children living in a defined rural Wisconsin population. Antibodies to Campylobacter jejuni and Escherichia coli O157:H7 lipopolysaccharide (O157 LPS) immunoglobulin G were measured, and the incidence of clinic visits for diarrheal illness was determined. Risk factors were assessed in a telephone interview. There were 363 children (59%) with C. jejuni antibodies (seropositive for >or=2 immunoglobulin classes) and 86 (14%) with O157 LPS antibodies. Increasing age and farm residence were independently associated with C. jejuni seropositivity by multivariate analysis. O157 LPS antibodies were independently associated with increasing age, female sex, manure contact, and sheep contact. The incidence of clinically recognized diarrhea was similar among children with and without antibodies to C. jejuni and O157 LPS, but the clinic visit rate for diarrhea was 46% lower among farm-resident children. These results are consistent with reduced occurrence of clinical illness from repeated antigenic stimulation in a farm environment.

Environmental isolates of Citrobacter braakii that agglutinate with Escherichia coli O157 antiserum but do not possess the genes responsible for the biosynthesis of O157 somatic antigen

While searching for Escherichia coli O157 in the aquatic environment of Calcutta using an immunodetection procedure, we fortuitously detected five strains of Citrobacter braakii, which cross-reacted with the commercially available O157 polyvalent antiserum. The five C. braakii isolates gave positive results when a sensitive dot-ELISA was performed with E. coli O157 monoclonal antibody. Further, the O157 monoclonal antibody recognized the bands of proteinase K treated whole cells of lipopolysaccharide of all the C. braakii isolates. Apart from weak reactions with two or three of the DNA probes, all the C. braakii strains did not hybridize with the other probes spanning the minimum region required for O157 O-antigen biosynthesis. These strains did not possess any of the virulence genes that are commonly found in the Shiga toxin-producing E. coli (STEC) specially the serotype O157: H7. Therefore, it appears that the serological cross-reaction between C. braakii and E. coli O157 antiserum is based on structural mimicry between the O-polysaccharide of C. braakii and E. coli O157.

An adapted ImmunoMagnetic cell separation method for use in quantification of Escherichia coli O157:H7 from bovine faeces

Detection of Escherichia coli O157:H7 organisms in food, clinical or environmental samples is necessary for diagnosis of infection and epidemiological investigations. However, this pathogen may be present in low numbers and difficult to identify among high numbers of other background bacteria. In order to increase the sensitivity of culture- and PCR detection, pre-enrichment of E. coli O157:H7 in broth culture combined with ImmunoMagnetic cell Separation (IMS) is routinely employed. These methods, although able to detect levels as low as 2 cfu/g (from 10 to 25 g samples), are qualitative detection strategies only. If the actual numbers of E. coli O157:H7 are to be quantified, growth enrichment must be excluded and the organisms isolated directly from the sample of interest. Such quantification is necessary, for example, to determinate contamination levels on beef carcasses and for determination of bacterial numbers in in vivo gene expression studies. In the present study, it was not possible to recover organisms from bovine faecal suspensions using the customary IMS system and so a range of alternative buffers and other paramagnetic beads was tested. Combination of a 6.2-microm diameter bead with a detergent-based buffer gave optimal recovery of E. coli O157:H7 organisms from faecal suspensions. This system was validated for recovery of E. coli O157:H7 by comparing it with that obtained with the standard Dynabeads IMS protocol, using both the traditional broth enrichment method and a quantitative detection approach. We conclude that a 6.2-microm diameter Aureon bead can be used for quantitative isolation of E. coli O157:H7 directly from bovine faeces and, for this purpose, is preferred to the 2.8-microm diameter Dynal bead.

Serum antibody levels against select bacterial pathogens in Atlantic bottlenose dolphins, Tursiops truncatus, from Beaufort NC USA and Charleston Harbor, Charleston, SC, USA

Concern over the emergence of zoonotic diseases in marine organisms is growing. In response to this concern, this study set out to measure antibody activities against bacterial pathogens in Atlantic bottlenose dolphins, Tursiops truncatus, from the coastal estuaries of NC and SC, USA. Individuals from Charleston SC harbor, a heavily industrialized shipping harbor estuary, and from Beaufort NC, a non-shipping estuary, were examined. Purified IgG was obtained from pooled sera using ammonium sulfate precipitation steps and protein-G procedures, which was then used to generate a panel of IgG-specific monoclonal antibodies. Two of these antibodies, mAbs BB-10-2 (IgG1) and BB-32-2 (IgG2b), were then used to determine total serum IgG concentrations using a sandwich capture ELISA. Circulating IgG levels were variable between individuals and between the two pods. MAb BB-10-2 was then used in an indirect ELISA to determine serum antibody activities against several common marine bacteria as well as the human pathogens E. coli and E. coli strain 0157:H7, Vibrio parahemolyticus, V. vulnificus, V. cholerae, Mycobacteria marinum, M. fortuitum, and M. chelonae. The highest antibody activities were against mycobacteria, two of which are zoonotic pathogens. Males had the highest antibody activities, thus suggesting low cell-mediated immunity against intracellular pathogens in these individuals. T-cell proliferation in response to Con-A, an indicator of cell-mediated immune function, was then measured in the Beaufort population. Males had the lowest proliferation responses, however a negative correlation between antibody activities and T-cell proliferation in individuals could not be established for either of the Mycobacteria species. Overall, antibody activities against all bacteria, including innocuous species such as V. anguillarum, V. natrigens, and M. xenopi were highly variable between individual dolphins and the two pods, with some animals exhibiting very high activities. These studies suggests that dolphin populations should be monitored by following the health and seroprevalence of pathogens of interest in select individual animals over time.

A murine model of enterohemorrhagic Escherichia coli O157:H7 infection to assess immunopotentiating activity of drugs on mucosal immunity: effect of drugs

An enterohemorrhagic Escherichia coli (EHEC) O157 oral infection murine model was established to examine the potentiating activity of drugs on mucosal immune responses. Groups of ICR mice inoculated intragastrically with 10(11) CFU/kg EHEC O157 showed chronic intestinal infection with the pathogen that persisted over 3 weeks and resulted in the synthesis of relatively high levels of antigen specific fecal IgA antibody. Intraperitoneal administration of 80 NU/kg Neurotropin, an immunopotentiator, augmented the antigen specific mucosal immune responses to EHEC O157. On the other hand, FK506 clearly suppressed the response. To further document the augmenting effect of Neurotropin on mucosal immune responses, mice were immunized intranasally with a mixture of ovalbumin and cholera toxin. Co-administration of 80 NU/kg Neurotropin significantly potentiated the synthesis of fecal IgA and serum IgG antibodies. These results suggest that Neurotropin has potential as a mucosal adjuvant to promote secretory IgA antibody production and that the mice model of oral infection with EHEC O157 is useful for immunopharmacological studies of bacterial infection-defensive mucosal immune responses.

Serology and genetics of the flagellar antigen of Escherichia coli O157:H7a,7c

Among Escherichia coli strains of the O55:H7 serovar, which is considered the ancestor of Shiga toxin-producing E. coli (STEC) O157:H7, two subtypes, H7a,7b and H7a,7c (briefly, H7a,b and H7a,c, respectively), of the H7 flagellar antigen have been described previously [J. Wright and R. Villanueva, J. Hyg. (Camb.) 51:39-48, 1953; Y. A. Ratiner and V. A. Sinelnikova, Zh. Microbiol. Epidemiol. Immunobiol. 3:111-116, 1969). We have now studied 13 STEC O157:H7 strains and 1 O55:H7 strain that were epidemiologically unrelated, that originated from six countries on two continents, and that had different profiles when analyzed by multilocus enzyme electrophoresis, pulsed-field gel electrophoresis, and PCR for stx and eae. They were all found to possess the H7a,c flagellar antigen. Serum cross-absorption assays confirmed that their H antigens were indistinguishable from each other and from that of E. coli O55:H7a,c but differed from the standard H7a,b antigen of E. coli H test strain U5/41. It was shown by phage-mediated transduction that the flagellin genes for these two H-antigen subserotypes were alleles of the E. coli fliC locus. On the basis of the serological data obtained in this study and the molecular characteristics of E. coli fliC(H7) alleles recently published, it is inferred that H7a,c and H7a,b are the main serological subtypes of the group of E. coli H7 flagellins.

Antibody repertoire development in fetal and neonatal piglets. VIII. Colonization is required for newborn piglets to make serum antibodies to T-dependent and type 2 T-independent antigens

Cesarean-derived piglets were reared for 5 wk under germfree conditions or monoassociated with a benign Escherichia coli (G58-1) or a enterohemorrhagic strain (933D) derived from O157:H7, and immunized i.p. with the T-dependent (TD) Ags fluorescein-labeled (FL) keyhole limpet hemocyanin or trinitrophenylated (TNP) keyhole limpet hemocyanin and the type 2 T-independent Ags TNP-Ficoll or FL-Ficoll. Only colonized piglets showed an increase in serum IgG, IgA, and IgM and had serum Abs to FL, TNP, and colonizing bacteria. While serum Abs to FL or TNP appeared following colonization alone, secondary responses were restricted to piglets immunized using TD carriers. While animals colonized with 933D had significantly higher total serum IgG and IgM levels and specific IgG Abs than those colonized with G58-1, no differences were seen in serum IgA levels, B cell diversification in the ileal Peyer's patches, and specific activity (ELISA activity per micrograms of Ig) of pre-boost serum IgG and IgM anti-TNP and anti-FL Abs. Serum IgA Abs to TNP, FL, or bacteria were not detected. Ag-driven responses, as measured by an increase in specific Ab activity, were only observed in secondary responses to TD Ags and to colonizing, pathogenic E. coli. We propose that germline-encoded, isotype-switched B cells in newborn piglets differentiate to Ab-secreting cells 1) after stimulation by bacteria-activated APCs or 2) through direct stimulation by bacterial products. We further propose that Ag-driven systemic responses require both bacterial colonization and TD Ags translocated to the peritoneum.

Production of serum antibodies that recognise epitopes located on the R3 region of Escherichia coli core lipopolysaccharides by patients infected with strains of enterohaemorrhagic E. coli

Antibody-antigen cross-reactions were examined with sera from patients with Escherichia coli O157 infection and lipopolysaccharide (LPS) purified from a range of enterohaemorrhagic E. coli (EHEC) including those belonging to serogroups O26, O103, O111, O145 and O157. Six of 10 patients infected with an O157 EHEC produced serum antibodies that cross-reacted with common LPS-core epitopes, which were expressed by 23 of 33 strains of EHEC examined. These common LPS-core epitopes were also present on strains of E. coli O26 which did not produce verocytotoxin. These cross-reacting antibodies did not influence the basic immunoblotting procedures used for the routine serodiagnosis of infections with E. coli O157.

Novel single-tube agar-based test system for motility enhancement and immunocapture of Escherichia coli O157:H7 by H7 flagellar antigen-specific antibodies

This paper describes a novel single-tube agar-based technique for motility enhancement and immunoimmobilization of Escherichia coli O157:H7. Motility indole ornithine medium and agar (0.4%, wt/vol) media containing either nutrient broth, tryptone broth, or tryptic soy broth (TSBA) were evaluated for their abilities to enhance bacterial motility. Twenty-six E. coli strains, including 19 O157:H7 strains, 1 O157:H(-) strain, and 6 generic E. coli strains, were evaluated. Test bacteria were stab inoculated in the center of the agar column, and tubes were incubated at 37 degrees C for 18 to 96 h. Nineteen to 24 of the 26 test strains (73.1 to 92.3%) were motile in the different media. TSBA medium performed best and was employed in subsequent studies of motility enhancement and H7 flagellar immunocapture. H7 flagellar antiserum (30 and 60 micro l) mixed with TSBA was placed as a band (1 ml) in the middle of an agar column separating the top (3-ml) and bottom (3-ml) agar layers. The top agar layer was inoculated with the test bacterial strains. The tubes were incubated at 37 degrees C for 12 to 18 h and for 18 to 96 h. The specificity and sensitivity of the H7 flagellar immunocapture tests were 75 and 100%, respectively. The procedure described is simple and sensitive and could be adapted easily for routine use in laboratories that do not have sophisticated equipment and resources for confirming the presence of H7 flagellar antigens. Accurate and rapid identification of H7 flagellar antigen is critical for the complete characterization of E. coli O157:H7, owing to the immense clinical, public health, and economic significance of this food-borne pathogen.

Current progress in enteropathogenic and enterohemorrhagic Escherichia coli vaccines

Enteropathogenic and enterohemorrhagic Escherichia coli are important causal agents of infectious diarrhea, particularly amongst pediatric populations. While enteropathogenic E. coli is a significant health threat in developing countries, enterohemorrhagic E. coli causes sporadic, sometimes deadly outbreaks of hemorrhagic colitis, with a serious complication, hemolytic uremic syndrome, ocurring in a proportion of cases. This review discusses the pathogenesis of enterohemorrhagic and enteropathogenic E. coli, the host immune response and the current application of this knowledge towards efficacious vaccine strategies. Several lines of investigation indicate the feasibility of such strategies and justify further development of a vaccine targeting these significant intestinal pathogens.