Indirect hemagglutination employing enterobacterial common antigen and Yersinia somatic antigen: a technique to differentiate brucellosis from infections involving cross-reacting Yersinia enterocolitica

Efficacy of several serological tests and antigens for diagnosis of bovine brucellosis in the presence of false-positive serological results due to Yersinia enterocolitica O:9

Yersinia enterocolitica O:9 bears a smooth lipopolysaccharide (S-LPS) of Brucella sp. O-chain A+C/Y epitopic structure and is a cause of false-positive serological reactions (FPSR) in standard tests for cattle brucellosis. Brucella S-LPS, cross-reacting S-LPSs representing several O-chain epitope combinations, Brucella core lipid A epitopes (rough LPS), Brucella abortus S-LPS-derived polysaccharide, native hapten polysaccharide, rough LPS group 3 outer membrane protein complexes, recombinant BP26, and cytosolic proteins were tested in enzyme-linked immunosorbent assays (ELISA) and precipitation tests to detect cattle brucellosis (sensitivity) and to differentiate it from FPSR (specificity). No single serological test and antigen combination showed 100% sensitivity and specificity simultaneously. Immunoprecipitation tests with native hapten polysaccharide, counterimmunoelectrophoresis with cytosolic proteins, and a chaotropic ELISA with Brucella S-LPS were 100% specific but less sensitive than the Rose Bengal test, complement fixation, and indirect ELISA with Brucella S-LPSs and native hapten or S-LPS-derived polysaccharides. A competitive ELISA with Brucella S-LPS and M84 C/Y-specific monoclonal antibody was not 100% specific and was less sensitive than other tests. ELISA with Brucella suis bv. 2 S-LPS (deficient in C epitopes), Escherichia hermannii S-LPSs [lacking the contiguous alpha-(1-2)-linked perosamine residues characteristic of Y. enterocolitica S-LPS], BP26 recombinant protein, and Brucella cytosolic fractions did not provide adequate sensitivity/specificity ratios. Although no serological test and antigen combination fully resolved the diagnosis of bovine brucellosis in the presence of FPSR, some are simple and practical alternatives to the brucellin skin test currently recommended for differential diagnosis.

Characterization of a monoclonal antibody specific for Brucella smooth lipopolysaccharide and development of a competitive enzyme-linked immunosorbent assay to improve the serological diagnosis of brucellosis

The reactivity of monoclonal antibody (MAb) 12G12 was analyzed in regard to the main biovars of Brucella species and some members of the families Enterobacteriaceae and Vibrionaceae which present serological cross-reactions with the smooth lipopolysaccharide (S-LPS) of Brucella species. This MAb was strictly directed against the common specific epitope of the Brucella S-LPS. It recognized all of the smooth Brucella strains and biovars except B. suis biovar 2. In order to improve the specificity of the serological diagnosis of brucellosis, a competitive enzyme-linked immunosorbent assay (cELISA) was developed with the horseradish peroxidase-conjugated MAbs 12G12 and S-LPS of B. melitensis Rev1. The specificity of the cELISA was analyzed with 936 serum samples from healthy cattle. The assay was evaluated with sera from heifers (n = 18) experimentally infected with B. abortus 544. After infection, the performance of the cELISA was in agreement with those of the complement fixation test and the rose Bengal plate test. Finally, the specificity of the assay was also evaluated in regard to false-positive serological reactions by using sera from heifers experimentally infected with Yersinia enterocolitica 0:9 (n = 4) and with field sera presenting false-positive reactions (n = 74). The specificity of the cELISA was greater than the specificities of the complement fixation test and the rose Bengal plate test. Indeed, the new assay detected only 31 of the 101 false-positive serum samples detected by at least one serological test.

Infection of cattle with Yersinia enterocolitica O:9 a cause of the false positive serological reactions in bovine brucellosis diagnostic tests

During the last four years, an increasing number of cattle herds were classified positive by brucellosis screening tests in areas of Belgium and France free of the disease. No clinical symptom of brucellosis was reported in these animals and no Brucella abortus strains were isolated. After two years, no brucellosis outbreak was registered in all of the herds concerned. On this basis, all the serological reactions observed were classified as false positive. An ELISA using Yersinia Outer membrane Proteins (YOPs) as antigens was developed in order to discriminate between a Yersinia enterocolitica O:9 infection and a Brucella abortus infection. Antibodies against YOPs were detected in sera from Y. enterocolitica O:9 experimentally infected cattle (n = 4) but not in sera from B. abortus experimentally infected cattle (n = 4). In a field study, 66.7% of the 174 serum samples from cattle presenting false positive serological reactions showed anti-YOPs antibodies whereas only 10% of 454 sera, classified negative by the brucellosis screening tests, showed anti-YOPs antibodies. Our results suggest that infections with Y. enterocolitica O:9 may cause false positive reactions in brucellosis testing.

Differentiation of serological responses to Yersinia enterocolitica serotype O9 and Brucella species by immunoblot or enzyme-linked immunosorbent assay using whole bacteria and Yersinia outer membrane proteins

Serum samples from 134 patients showing by the microagglutination test serological cross-reactivity between Yersinia enterocolitica serotype O9 and Brucella spp. were analyzed by immunoblot and enzyme-linked immunosorbent assay techniques for the presence of antibodies directed against plasmid-encoded, yersinia-associated outer membrane proteins (OMPs). Since these OMPs are exclusively expressed in pathogenic strains of Yersinia spp., this characteristic was chosen for serological differentiation of infections caused by these bacteria. The presence of antibodies against plasmid-encoded OMPs of pathogenic Yersinia spp. in patient sera appeared to be a suitable means to identify acute or recent infection with Y. enterocolitica serotype O9, whereas the failure to detect such antibodies indicated an acute or recent infection with Brucella spp.

ECA, the enterobacterial common antigen

Enterobacterial common antigen (ECA) is a family-specific surface antigen shared by all members of the Enterobacteriaceae and is restricted to this family. It is found in freshly isolated wild-type strains as well as in laboratory strains like Escherichia coli K-12. The family specificity of ECA can be used for taxonomic and diagnostic purposes. ECA is located in the outer leaflet of the outer membrane. It is a glycophospholipid built up by an aminosugar heteropolymer linked to an L-glycerophosphatidyl residue. In a few rough mutants, in addition, the sugar chain can be bound to the complete lipopolysaccharide (LPS) core. Recently, for Shigella sonnei a lipid-free cyclic form of ECA was reported. The genetical determination of ECA is closely related to that of lipopolysaccharide. For biosynthesis of ECA and LPS partly the same sugar precursors and the same carrier lipid is used.

A review of enzyme immunoassay for detection of antibody to Brucella abortus in cattle

Enzyme immunoassay has gained wide acceptance for serological diagnosis of bovine brucellosis because of its ability to detect antibody of all isotypes unlike the conventional tests. The indirect enzyme immunoassay, however, presents several parameters that require careful analysis. These parameters include the choice of antigen and antiglobulin-enzyme conjugate reagents for use in the assay, dealing with the large amount of data the semi-automatic or automatic assay can generate and the inter- and intralaboratory standardization and quality control. This review considers the various methods described in the literature and, briefly, how some of the problems have been overcome or how they might be dealt with.

Yersinia enterocolitica associated with third trimester abortion in buffaloes

A group of buffaloes aborted at the third trimester of their gestational period. Yersinia enterocolitica was isolated from all cases. All aborted animal sera had high antibody titres against Y. enterocolitica antigen which crossreacted significantly with Brucella abortus antigen. All animals were culturally negative after intrauterine infusion of gentamycin sulphate (160 mg/day) for three consecutive days.

Enzyme immunoassay of the antibody response to Brucella and Yersinia enterocolitica 09 infections in humans

An enzyme immunoassay, with phenol-water extracted lipopolysaccharide (LPS) from Brucella abortus as antigen, was used to detect the class-specific antibody response in sera from 173 patients with B. abortus, B. melitensis or B. suis infection. Sera from 30 patients with salmonellosis, yersiniosis or tularaemia and from 25 healthy individuals served as controls. The B. abortus LPS antigen permitted a safe diagnosis of acute and chronic brucellosis with high IgM and rising IgG titres in sera collected in the acute stage of the disease, and with elevated IgG titres only in the chronic stage. The B. abortus LPS antigen also permitted a specific diagnosis with the exception of the high titres estimated in sera from patients with Yersinia enterocolitica 09 infection. The problem with that well-known reciprocal cross-reactivity was overcome by using two additional antigens: Y. enterocolitica 09 native and periodate oxidized and borohydride reduced LPS preparations. In sera from patients with brucellosis high titres were estimated against all three antigens, whereas in sera from patients with yersiniosis caused by serotype 09 high titres were measurable only with the B. abortus and the Y. enterocolitica native LPS antigens. These data suggest that the B. abortus and Y. enterocolitica 09 LPS share one antigenic determinant resistant to periodate oxidation and borohydride reduction, and that in addition the Y. enterocolitica 09 LPS has a determinant which is sensitive to periodate oxidation and borohydride reduction.

Measurement of immunoglobulin M, immunoglobulin G, and immunoglobulin A antibodies against Yersinia enterocolitica by enzyme-linked immunosorbent assay: comparison of lipopolysaccharide and whole bacterium as antigen

An enzyme-linked immunosorbent assay (ELISA) for the detection and quantitation of human immunoglobulin M (IgM), IgG, and IgA antibodies against Yersinia enterocolitica by using lipopolysaccharides as antigens is described. The results obtained with the lipopolysaccharide ELISA were compared with the results of the whole bacterium ELISA. The correlations observed were good for each immunoglobulin class. Cross-reactions between Y. enterocolitica serotypes O:3 and O:9, Yersinia pseudotuberculosis IA, and Brucella abortus were studied by human and rabbit antisera in the whole bacterium and lipopolysaccharide ELISAs and by rabbit antisera using ELISA inhibition. The greatest cross-reactivity observed was that of the anti-Brucella serum with Y. enterocolitica O:9 in the whole bacterium ELISA. In the lipopolysaccharide ELISA this cross-reaction was not demonstrable with the rabbit antiserum, but it was strong with the human antiserum. However, differential diagnosis was possible with ELISA inhibition. On the basis of our experience, we are now routinely using whole bacterium ELISA for the determination of class-specific Yersinia antibodies, and potential cross-reactions are controlled by the ELISA inhibition.