Performance of competitive and indirect enzyme-linked immunosorbent assays, gel immunoprecipitation with native hapten polysaccharide, and standard serological tests in diagnosis of sheep brucellosis.
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Competitive and standard enzyme-linked immunosorbent assays (ELISAs), rose bengal (RB), complement fixation, and agar gel immunoprecipitation with native hapten (AGID-NH) were compared by using sera from Brucella-free, Brucella melitensis-infected, and B. melitensis Rev1-vaccinated sheep. The most sensitive tests were indirect ELISA and RB, and the most specific tests were AGID-NH and competitive ELISA. We show that RB followed by AGID-NH is a simple and effective system for diagnosing sheep brucellosis. (+info)
Modulation of endocytosis in nuclear factor IL-6(-/-) macrophages is responsible for a high susceptibility to intracellular bacterial infection.
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Activated macrophages kill bacteria, a function known to depend on the expression of NF-IL-6. Here, it is demonstrated that the attenuated Brucella abortus vaccine strain 19 replicates much better in NF-IL-6-/- than in NF-IL-6(+/+) and NF-IL-6(+/+)-activated murine macrophages and at levels comparable to those observed in normal macrophages infected with the pathogenic strain 2308. The role of NF-IL-6 in the inhibition of intracellular bacterial replication is related to its control of endocytosis and membrane fusion between endosomes and Brucella-containing phagosomes. Addition of the granulocyte-CSF (G-CSF), whose induction is impaired in NF-IL-6(-/-) macrophages, restores both endocytosis and the morphology of endosomes, together with bactericidal activity. Regulation of membrane traffic in endocytosis by G-CSF whose expression is controlled by NF-IL-6 may explain how a host cell can control intracellular bacterial replication. (+info)
Genomic fingerprinting and development of a dendrogram for Brucella spp. isolated from seals, porpoises, and dolphins.
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Genomic DNA from reference strains and biovars of the genus Brucella was analyzed using pulsed-field gel electrophoresis (PFGE). Fingerprints were compared to estimate genetic relatedness among the strains and to obtain information on evolutionary relationships. Electrophoresis of DNA digested with the restriction endonuclease XbaI produced fragment profiles for the reference type strains that distinguished these strains to the level of species. Included in this study were strains isolated from marine mammals. The PFGE profiles from these strains were compared with those obtained from the reference strains and biovars. Isolates from dolphins had similar profiles that were distinct from profiles of Brucella isolates from seals and porpoises. Distance matrix analyses were used to produce a dendrogram. Biovars of B. abortus were clustered together in the dendrogram; similar clusters were shown for biovars of B. melitensis and for biovars of B. suis. Brucella ovis, B. canis, and B. neotomae differed from each other and from B. abortus, B. melitensis, and B. suis. The relationship between B. abortus strain RB51 and other Brucella biovars was compared because this strain has replaced B. abortus strain 19 for use as a live vaccine in cattle and possibly in bison and elk. These results support the current taxonomy of Brucella species and the designation of an additional genomic group(s) of Brucella. The PFGE analysis in conjunction with distance matrix analysis was a useful tool for calculating genetic relatedness among the Brucella species. (+info)
Immunity to Brucella in mice vaccinated with a fraction (F8) or a killed vaccine (H38) with or without adjuvant. Level and duration of immunity in relation to dose of vaccine, recall injection and age of mice.
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Immunity to Brucella in the mouse, assessed by bacterial spleen counts 15 days after intraperitoneal inoculation of a standard challenge of B. abortus 544, has been studied with two vaccines, one experimental, composed of a fraction of the bacterial cell-wall (F8) extracted from B. abortus 99, the other of killed whole bacteria, B. melitensis 53 H38, taken as reference (H38). The level of primary immunity depended on the dose of vaccine, the presence of oil adjuvant and the age of the mouse. The presence of adjuvant enabled the immunization to F8 to continue beyond the first month, to reach its maximum around the fourth month, and to remain stable for at least 7 months. A booster injection 3 or 6 months after the primary vaccination reinforced existing immunity but did not increase it beyond a certain level. The effect of the recall injection was clearly demonstrated with low doses which gave a lower level of primary immunity. (+info)
Plaque-forming cells in mice after experimental infection with Brucella abortus.
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Cells producing antibody to brucella lipopolysaccharide were detected in spleens of mice infected with Brucella abortus 19 by a hemolytic plaque assay. The appearance of immunoglobulin M-producing cells preceded humoral antibodies. The primary plaques were observed 5 days after inoculation, and they were still present by day 70. (+info)
Effect of early antibiotic treatment on the antibody response to cytoplasmic proteins of Brucella melitensis in mice.
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To test whether antibiotic therapy hampers the antibody response to Brucella antigens, 30 BALB/c mice were infected with Brucella melitensis H38 and randomized for treatment with doxycycline administered intraperitoneally for 42 days starting at 7 or 28 days postinfection (p.i.) (groups DOX7 and DOX28, respectively) or for no treatment (control group). Antibodies to smooth lipopolysaccharide (LPS) reached peak levels (mean optical density [OD] = 2.618) between days 56 and 70 p.i. in the control group, and similar peak levels (mean OD = 2.486) were observed in the DOX28 group, but significantly lower peak levels (mean OD = 0.821) were observed at 28 days p.i. in the DOX7 group. The antibody response against cytoplasmic proteins depleted of LPS (CPs) reached maximal levels (mean OD = 2.402) between days 56 and 70 p.i. in the control group, but no response was detected in the DOX7 group. Anti-CP antibodies were detected in only three animals from the DOX28 group, at levels significantly lower than those in the control group (mean maximal OD = 0.791). The pattern of antibody response to an 18-kDa cytoplasmic protein of Brucella spp. was similar to that against the CP antigen. This study shows that early antibiotic treatment affects the antibody response of mice to cytoplasmic proteins of Brucella and, to a lesser extent, to LPS. (+info)
The siderophore 2,3-dihydroxybenzoic acid is not required for virulence of Brucella abortus in BALB/c mice.
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2,3-Dihydroxybenzoic acid (DHBA) is the only siderophore described for Brucella, and previous studies suggested that DHBA might contribute to the capacity of these organisms to persist in host macrophages. Employing an isogenic siderophore mutant (DeltaentC) constructed from virulent Brucella abortus 2308, however, we found that production of DHBA is not required for replication in cultured murine macrophages or for the establishment and maintenance of chronic infection in the BALB/c mouse model. (+info)
Destructive aortic valve endocarditis from Brucella abortus: survival with emergency aortic valve replacement.
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Brucella abortus infection of the aortic valve caused acute aortic regurgitation leading to severe left ventricular failure in a 62-year-old man. He made an excellent recovery after emergency aortic valve replacement. This is the third reported case of successful heart valve replacement for Brucella endocarditis and the second such case involving the aortic valve. (+info)