Protective efficacy of a genetic subunit bacterin against edema disease of swine in mice.

The exotoxin SLT-IIeB from the Escherichia coli Ee strain was expressed in E. coli, and the recombinant protein was purified, mixed with the Ee strain, then emulsified with oil-emulsion adjuvants to obtain a mixed subunit bacterin. Groups of Kunming mice were immunized at weeks 0 and 2, and challenged intraperitoneally with the Ee strain at week 4. Antibodies were detected by ELISA and an agglutination test. After the second immunization, the antibody level increased and the rate of immune protection against the Ee strain was 70 and 91.7% in the subunit bacterin and bacterin groups, respectively. Therefore, the mixed subunit bacterin provided good protection against the homologous Ee strain, which provides a basis for further research, into high-efficacy vaccines against porcine edema disease.

Polymorphism of M307 of the FUT1 gene and its relationship with some immune indexes in Sutai pigs (Duroc x Meishan).

The alpha (1,2)fucosyltransferase (FUT1) gene has been identified as a candidate gene for controlling the expression of the enterotoxigenic Escherichia coli (ETEC) F18 receptor. Polymorphisms were detected at the M307 position in FUT1 of a breeding base population of Sutai pigs and their correlations to immune parameters analyzed. After digestion by Hin6I, three genotypes were identified at M307, AA (frequency 0.235), AG (0.609), and GG (0.156), with significant deviation from Hardy-Weinberg equilibrium (P < 0.01). The hemoglobin and white blood cell count of the AA genotype pigs were significantly higher than those of AG and GG pigs (P < 0.05). The results indicated that AA pigs not only are resistant to edema disease and post-weaning diarrhea in piglets but also have relatively strong resistance to disease in general.

Ultrastructure and DNA fragmentation analysis of arterioles in swine infected with Shiga toxin-producing Escherichia coli.

Shiga toxins (Stx) produced by E. coli are potent cytotoxins that affect the vascular system. In humans, systemic toxemia causes renal glomerular damage manifested as hemolytic uremic syndrome. In swine, Stx-producing E. coli (STEC) cause edema disease that is characterized microscopically by segmental arteriolar smooth muscle cell (SMC) lesions. Our objectives were to characterize ultrastructurally and by TUNEL the type of death (apoptosis or necrosis) that occurs in SMCs during edema disease. Increased DNA fragmentation consistent with apoptosis was detected by TUNEL in arterioles of challenged pigs 14-15 days post inoculation. Ultrastructurally 3 grades of SMC lesions were distinguished: 1) Partial loss of SMCs, intercellular space filled with granular cellular debris admixed with membrane bound vacuoles; 2) Complete loss of SMCs; only granular cellular debris and clear vacuoles remained within basement membrane; 3) Inflammation of media; SMCs replaced by a rim of cellular debris located in the periphery of vessel wall. The most common lesion detected was grade 1 (9 ilea and 4 brains). We did not find apoptotic nuclear changes in SMCs or apoptotic inclusion bodies within resident cells. Our study indicates, that (1) Stx produced during edema disease does not cause SMC apoptosis 14-15 dpi; (2) SMCs undergo an array of changes from degeneration to necrosis.

Genotypic prevalence of the fimbrial adhesins (F4, F5, F6, F41 and F18) and toxins (LT, STa, STb and STx2e) in Escherichia coli isolated from postweaning pigs with diarrhoea or oedema disease in Korea.

A PCR was used to determine the genotypic prevalence of five fimbrial adhesins (F4, F5, F6, F41 and F18), two heat-stable enterotoxins (STa and STb), the heat-labile enterotoxin (LT), and the shiga toxin 2e (Stx2e) in 230 isolates of Escherichia coli from postweaning pigs with diarrhoea or oedema disease. Ninety-four (40.9 per cent) of the isolates carried genes for at least one of the fimbrial adhesins or toxins. Genes for the F18 fimbrial adhesin were detected in 18.3 per cent, and genes for F4, F6, F5 and F41 were detected in 10.0 per cent, 4.3 per cent, 1.7 per cent and 0.8 per cent of the isolates, respectively. Genes for STa, STb and LT were detected in 25.7 per cent, 15.2 per cent and 8.7 per cent of the isolates, respectively. Genes for Stx2e were detected in 36 (15.6 per cent) of the isolates, and among them 24 also contained the gene for F18ab and four also contained the gene for F18ac.

[A molecular test for the detection of E. coli F18 receptors: a breakthrough in the struggle against edema disease and post-weaning diarrhea in swine]. / Ein molekularer Test für den Nachweis des E.-coli-F18-Rezeptors: ein Durchbruch im Kampf gegen Oedemkrankheit und Absetzdurchfall beim Schwein.

Oedema disease and post-weaning diarrhoea in swine are associated with the colonization of the intestine with toxigenic Escherichia (E.) coli bacteria of various serotypes. Colonization depends on specific binding between adhesive fimbriae and receptors on the enterocytes. The demonstration of these receptors allows the identification of susceptible and resistant pigs. Direct sequencing of the alpha (1,2) fucosyltransferase gene (FUT1) in swine being either susceptible or resistant to adhesion by F18 fimbriated E.coli revealed a mutation at basepair 307 (M307). Analysis of the mutation in Swiss Landrace and Large White families showed close linkage with the locus controlling resistance and susceptibility to E.coli F18 adhesion (ECF18R). The FUT1 (M307) mutation is a good marker for selection of E.coli of F18 adhesion resistant animals. The mutation is found with variable frequencies in Duroc, Hampshire and Pietrain pigs as well.

Real-time PCR for differentiation of F18 variants among enterotoxigenic and Shiga toxin-producing Escherichia coli from piglets with diarrhoea and oedema disease.

One-step real-time PCR using one set of primers and four probes was developed for differentiation of F18 variants (F18 common, F18ab, F18ac, F18new variant) of enterotoxigenic (ETEC) and Shiga toxin-producing (STEC) Escherichia coli from piglets with diarrhoea and oedema disease. The limits of detection for F18common, F18ab, F18ac, and F18new variant were 10(7), 10(7), 10(5) and 10(7)colony forming units/g faeces, respectively. Of 94 Korean isolates of E. coli encoding F18, 70 were F18ac (43 STEC/ETEC, 4 STEC and 23 ETEC), 15 were F18ab (all STEC) and nine were F18new variant (1 STEC/ETEC, 7 STEC, 1 ETEC).