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Campylobacter fetusis recognized as a human and animal pathogen. The isolation and differentiation of C. fetusin diagnostic laboratories is hindered by its relatively slow growth and lack of distinguishing biochemical characteristics. We cloned and sequenced a 1581-bp DNA fragment, IG02, isolated from a C. fetusgenomic library. This fragment was used as a probe on DNAs extracted from C. fetusstrains and otherCampylobacterspecies: IG02 hybridized only with DNAs from C. fetusstrains. A PCR-based test was developed for the detection of C. fetus. A pair of oligonucleotide primers was designed to amplify a 141-bp fragment of IG02. The amplified product was analysed by a non-radioactive sandwich hybridization in microtiter plate using a capture oligonucleotide and a biotin-labelled oligonucleotide for the detection. The combination of PCR and non-radioactive microplate hybridization is a convenient method for the rapid detection of C. fetus.

PCR targeting the IS 6110has been considered specific for identification of Mycobacterium tuberculosisand is frequently applied to confirm the presence of this organism directly in biological specimens. However, several authors found that some M. tuberculosisstrains failed to hybridize with the IS 6110probe and other authors found that false-positive results may be obtained for clinical samples when some methods based on IS 6110are used. In the present study, the p27gene isolated from a cosmid library was found to be highly specific for M. tuberculosiscomplex strains and allowed us to develop a PCR-based assay for rapid detection and identification of this mycobacterium. One pair of primers and two oligonucleotide probes were successfully used to amplify and to detect the DNA of strains belonging to the M. tuberculosiscomplex. These primers and probes did not hybridize with DNA from any of the 21 other mycobacterial species tested. It is worth noting that the chosen primers and probes hybridize with DNA from the M. tuberculosisstrain with no IS 6110, furthermore no strain without p27was found among the 410 strains tested in the present study.

Setting: Northern and Southern areas of Vietnam. Objective: To study the correlation between DNA fingerprinting of 168 Mycobacterium tuberculosisstrains isolated from patients with a particular historical past (political separation of Vietnam for 20 years) and data about geographical origin, drug susceptibility, HIV infection and BCG vaccination status.

A Listeria monocytogenesUNA fragment, identified as part of the 23S rRNA gene and called B17, was used to type 266 L. monocytogenesstrains and 43 strains of other Listeriaspecies. Results were compared with those obtained: i) with pBA2 (which consists of a 2.3 kb Bacillus subtilisDNA fragment encoding 16S rRNA, inserted into the HinIIIsite of pBR322), a probe previously used for Listeriaand L. monocytogenesribotyping, and ii) with DNA macrorestriction profiles analysis. Twenty profiles were identified for L. monocytogenesusing pB17, three of which accounted for 87% of strains. This new rDNA probe had greater discriminatory power for serogroups 1/2 or 3 strains than for serogroup 4 strains. The number of varieties and the discrimination index were higher with this new probe than with pBA2, but DNA macrorestriction patterns analysis gave better discrimination between strains.

Two erythrocyte immunoassay techniques to detect the presence of Escherichia coli heat-labile enterotoxin (LTh) in stool supernatants and cell-free culture supernatants were compared. In the competitive assay, GM1 ganglioside was coated onto V-shaped-well microdilution plates and enterotoxin was coupled to sheep erythrocytes. As little as 0.8 ng of LTh per ml was detected by this method, which was based on the competition between the LTh of the test sample and the sensitized erythrocytes. The second assay made use of chimera antibody prepared by coupling polyclonal anti-LTh antibody to a monoclonal antibody specific for sheep erythrocytes. In this case, LTh, which was specifically bound to a GM1 ganglioside-coated plate, was detected by successively adding the chimera antibody and sheep erythrocytes. The limit of detection of the chimera antibody erythrocyte immunoassay was 0.2 ng/ml. Stool samples were collected from 167 infants hospitalized for diarrhea in the hospital of Noumea, New Caledonia. False-negative reactions due to proteases present in the stool samples were avoided by the addition of phenylmethylsulfonyl fluoride.

Biotin was covalently attached to antibodies, antigens and enzymes, and the effects of this labeling on the antigen and antibody binding capacity and on enzymatic activity were tested. Based on avidin-biotin interaction, the labeled proteins were used in quantitative enzyme-immunoassay and enzyme-immunohistochemical staining procedures. Two procedures were developed. In the first procedure, named the Bridged Avidin-Biotin (BRAB) technique four steps were used sequentially in order to quantify or detect an immobilized antigen: 1) incubation with biotin-labeled antibody; 2) incubation with avidin; 3) incubation with biotin-labeled enzyme; 4) measurement or histochemical staining of the enzyme. The technique is based on the observation that avidin possesses four active sites. In the second procedure, named the Labeled Avidin-Biotin (LAB) technique, biotin-labeled antibody and enzyme-labeled avidin are used sequentially. Enzyme-associated antigen is then quantified or revealed immunohistochemically. The optimal conditions for enzyme-immunoassay and enzyme-immunohistochemical staining using BRAB and LAB procedures were established.

A magnetic solid phase enzyme-linked immunosorbent assay (MELISA) for quantification of IgG antibodies to somatic and metabolic antigens of Paracoccidioides brasiliensis was developed. Activation of magnetic polyacrylamide agarose beads with concanavalin A was superior to glutaraldehyde activation, and test sensitivity was higher for somatic than for metabolic antigens. Comparative MELISA, counterimmunoelectrophoresis and erythroimmunoassay tests with sera from 33 proven cases of paracoccidioidomycosis, 14 cases of histoplasmosis and 20 normal human sera showed the MELISA could distinguish antibody levels in paracoccidioidomycosis from those in normal sera; however two sera from histoplasmosis cases cross-reacted in the MELISA. MELISA is a rapid test (5-6 h) and the results suggest it has considerable potential value for assay of anti-P. brasiliensis antibodies.

The erythro-immunoassay, a new serological procedure in which a hybrid antibody conjugate is able to bind erythrocytes, was used for the titration of antibodies against P. brasiliensis in sera from patients with paracoccidioidomycosis. A peptide-polysaccharide and a lyophilized yeast culture filtrate of P. brasiliensis were used as antigens. Absorption with dead Candida albicans whole cells was necessary to decrease cross reactions observed with heterologous sera. Erythroimmunoassay provides a sensitive system for titration of antibodies in paracoccidioidomycosis with serum dilutions up to 1:102000.

Visceral leishmaniasis, a chronic and often fatal disease, is caused by the protozoan parasite Leishmania donovani. Both specific and nonspecific antibodies are produced in the course of the disease, and autoantibodies may be involved in pathogenesis. Tubulin and actin have been found to be associated with L. donovani. To learn whether antiactin and antitubulin antibodies are present in visceral leishmaniasis, we tested sera from 263 infected dogs by enzyme-linked immunosorbent assay for antibodies to the antigens L. donovani, actin, and tubulin. All samples reacted positively with L. donovani, and a high percentage reacted positively with all three antigens. Sera from 202 uninfected dogs were also tested, none reacted with L. donovani antigen, although positive reactions were observed for 8 of the samples with actin or tubulin. It was found that the antibody-antigen reaction occurred at the Fab portion of the immunoglobulin molecule. Competitive enzyme immunoassays showed that the reaction was inhibited if the positive serum was first incubated with L. donovani antigen, actin, or tubulin and then tested by enzyme-linked immunosorbent assay. These results suggest that antiactin and antitubulin antibodies are present in the sera of dogs infected with visceral leishmaniasis.

An enzyme-linked immunosorbent assay (ELISA) for detection and quantification of antibodies antiParacoccidioides brasiliensis is described. Polystyrene plates have been used as solid phase to absorb P. brasiliensis metabolic yeast phase antigen. Twenty sera of proven paracoccidioidomycosis, 11 of histoplasmosis due Histoplasma capsulatum, 20 of aspergillosis and 20 human normal sera were tested. Ninety-five percent of the paracoccidioidomycosis sera had O.D. superior to 0.150 (from 0.163 to 2.650) at 1/400 serum dilution. ELISA assay was compared with counterimmunoelectrophoresis and erythro-immunoassay tests; a correlation was observed only with erythro-immunoassay. ELISA test should give new perspectives for the serodiagnosis of paracoccidioidomycosis.