Characteristics of Vero cytotoxin producing Escherichia coli associated with intestinal colonization and diarrhea in calves.

Isolates of Escherichia coli which produce Vero cytotoxin (VTEC) were obtained during 1983-1989 from calves raised in 5 north-central states of the USA. All of the calves experienced intestinal epithelial colonization by VTEC, diarrhea or both; twelve of the calves had bloody diarrhea. Twenty one isolates were serogroup O111 and the others were O103, O69, O45, 026, O5, or non-typable (4 isolates). All but one of the isolates hybridized with the CVD419 probe which identifies most VTEC strains. Thirty two isolates hybridized with the VT1 probe, 3 with both the VT1 and VT2 probes, and one with neither probe. The culture filtrate of the VT probe negative isolate was partially neutralized by SLT I monoclonal antibody. For the other isolates, the results of toxin neutralization by anti-SLT I and anti-SLT II monoclonal antibodies corresponded exactly with the VT1 and VT2 probe hybridization results. Three of the strains adhered in a localized manner to HEp-2 cells and Intestine 407 cells.

Immunocompromise in gnotobiotic pigs induced by verotoxin-producing Escherichia coli (O111:NM).

A verotoxin-producing Escherichia coli serotype O111:NM strain (strain 10049; verotoxin 1 positive) persistently infected experimentally inoculated gnotobiotic pigs, causing attaching-effecting intestinal lesions and chronic diarrhea. Experiments were performed to determine whether persistent infection might be associated with immunocompromise of the host of this organism. Pigs inoculated with this strain had a significant reduction in peripheral blood lymphocytes and lower antibody titers to sheep erythrocytes compared with control pigs. Compared with pigs given a verotoxin-negative pathogenic strain of the same serotype (O111:NM, strain 2430), pigs inoculated with the verotoxin-positive strain had lower peripheral lymphocyte counts and proliferative responses to concanavalin A, phytohemagglutinin, and pokeweed mitogens. The results of this study suggest that strain 10049 has an immunocompromising effect on gnotobiotic pigs.

Identification of two porcine brush border glycoproteins that bind the K88ac adhesin of Escherichia coli and correlation of these glycoproteins with the adhesive phenotype.

In this study, we identified two brush border glycoproteins (210 and 240 kDa) that bind both K88ac+ Escherichia coli and purified K88ac adhesin. The specificity of these binding glycoproteins for the K88ac adhesin was demonstrated in studies in which the binding of 35S-labeled K88ac+ E. coli and biotinylated K88ac adhesin to these glycoproteins was blocked in the presence of a 100-fold molar excess of unlabeled K88ac adhesin but not in the presence of the K99 adhesin. Pretreatment of adhesive brush borders with sodium metaperiodate destroyed both binding activities, indicating that the interaction between the K88ac adhesin and the binding glycoproteins requires the glycoprotein carbohydrate moiety. It was demonstrated previously that K88ac+ E. coli binds to adhesive brush borders but not to nonadhesive brush borders (R. Sellwood, R. A. Gibbons, G. W. Jones, and J. M. Rutter, J. Med. Microbiol. 8:405-411, 1975). In the present study, brush borders isolated from 10 different pigs were tested first for brush border adhesiveness and then for the presence of the binding glycoproteins. In all cases, the binding glycoproteins were detected only in the adhesive brush border preparations. These two binding glycoproteins may be the receptors used by K88ac+ ETEC to adhere to intestinal brush border cells. Their presence on adhesive brush borders and absence on nonadhesive brush borders may be the basis for resistance and susceptibility of pigs to K88ac+ ETEC infections.

Evaluation of a live avirulent Escherichia coli vaccine for K88+, LT+ enterotoxigenic colibacillosis in weaned pigs.

Live, avirulent Escherichia coli vaccine strains were constructed and tested for efficacy in preventing colibacillosis in 4-week-old pigs. Either or both of 2 plasmids were inserted into avirulent E coli strain G58-1 (0101:NM). These plasmids were pPMC4, which encodes for LTb subunits of heat-labile enterotoxin, and pDHF1, which encodes for K88ac fimbriae. Litter- and weight-matched pigs were removed from sows when they were 10 days old and vaccinated orally with the constructed strains or with G58-1 (negative control vaccine) when they were 2 weeks old and 5 days later. All pigs were challenge-inoculated with virulent E coli strain 3030-2 (O157:K88, LT+, STb+) 2 weeks after the first vaccination. Only 1 pig vaccinated with G58-1/pPMC4/pDHF1 developed diarrhea and none died following challenge inoculation. Seventeen of 31 control pigs developed diarrhea and 11 died. Of 18 pigs vaccinated with G58-1/pDHF1 then challenge-inoculated with the virulent strain, 5 developed diarrhea and 2 died. Fifteen of 18 litter- and weight-matched controls developed diarrhea and 8 died. When compared with G58-1 (negative control), G58-1/pPMC4 afforded no protection to pigs challenge-inoculated with 3030-2.

Comparison of seroagglutination, ELISA, and indirect fluorescent antibody staining for the detection of K99, K88, and 987P pilus antigens of Escherichia coli.

Seroagglutination (SAT), enzyme-linked immunosorbent assay (ELISA), and indirect fluorescent antibody staining tests (IFAT) were compared for reliability in the detection of pilus antigens K99, K88, and 987P of Escherichia coli. Test sensitivities were compared using mixtures of piliated bacteria of several strains diluted to a constant optical density with a nonpiliated strain. Relative sensitivities and specificities of the 3 tests were also compared using 55 E. coli strains that had previously been serotyped and characterized for pilus genes by DNA probe. Although specificity was not a serious problem with any of the tests, the SAT was relatively nonsensitive. The IFAT showed the greatest sensitivity of the 3 tests in detecting K88, K99, and 987P E. coli.