pagP is required for resistance to antibody-mediated complement lysis during Bordetella bronchiseptica respiratory infection.
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To efficiently colonize and persist in the lower respiratory tract, bacteria must survive multiple host immune mechanisms. Bordetella bronchiseptica is a gram-negative respiratory pathogen that naturally infects mice and persists in the lower respiratory tract for up to 49 days postinoculation. In this work, we examined the effect of mutation of the pagP gene on the persistence of B. bronchiseptica in the lower respiratory tract of mice. The pagP gene encodes a palmitoyl transferase that is responsible for the addition of a palmitoyl group to the lipid A region of B. bronchiseptica lipopolysaccharide. Data presented here confirm that a B. bronchiseptica deltapagP mutant demonstrates defective persistence in the lower respiratory tract of wild-type mice. We hypothesized that the defective persistence of the B. bronchiseptica deltapagP mutant was due to an increased susceptibility of this mutant to a host immune response. In vivo data indicate that both B cells and the complement component C3 are required for the reduced bacterial numbers of the deltapagP mutant on day 14 postinoculation. In addition, an in vitro complement killing assay demonstrated that B. bronchiseptica exhibits pagP-dependent resistance to antibody-mediated complement killing at low concentrations of immune serum. Taken together, these results suggest that pagP is required for B. bronchiseptica to resist antibody-mediated complement lysis during respiratory infection. (+info)
Chronic cholangitis caused by Bordetella hinzii in a liver transplant recipient.
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Bordetella hinzii was isolated in four biliary specimens collected over 6 months from a liver transplant recipient with cholangitis. The isolates were resistant to most beta-lactam antibiotics and fluoroquinolones. Molecular typing was performed by pulsed-field gel electrophoresis. These data add cholangitis to the spectrum of disease manifestations caused by B. hinzii. (+info)
Bordetella type III secretion and adenylate cyclase toxin synergize to drive dendritic cells into a semimature state.
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Bordetella bronchiseptica establishes persistent infection of the murine respiratory tract. We hypothesize that long-term colonization is mediated in part by bacteria-driven modulation of dendritic cells (DCs) leading to altered adaptive immune responses. Bone marrow-derived DCs (BMDCs) from C57BL/6 mice infected with live B. bronchiseptica exhibited high surface expression of MHCII, CD86, and CD80. However, B. bronchiseptica-infected BMDCs did not exhibit significant increases in CD40 surface expression and IL-12 secretion compared with BMDCs treated with heat-killed B. bronchiseptica. The B. bronchiseptica type III secretion system (TTSS) mediated the increase in MHCII, CD86, and CD80 surface expression, while the inhibition of CD40 and IL-12 expression was mediated by adenylate cyclase toxin (ACT). IL-6 secretion was independent of the TTSS and ACT. These phenotypic changes may result from differential regulation of MAPK signaling in DCs. Wild-type B. bronchiseptica activated the ERK 1/2 signaling pathway in a TTSS-dependent manner. Additionally, ACT was found to inhibit p38 signaling. These data suggest that B. bronchiseptica drive DC into a semimature phenotype by altering MAPK signaling. These semimature DCs may induce tolerogenic immune responses that allow the persistent colonization of B. bronchiseptica in the host respiratory tract. (+info)
Comparison of culture and PCR for detection of Bordetella pertussis and Bordetella parapertussis under routine laboratory conditions.
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A PCR assay for the detection of Bordetella pertussis and Bordetella parapertussis was compared with the conventional culture method under routine laboratory conditions. Detection of B. pertussis was based on the amplification of a section of the IS481 insertion sequence and confirmation of positive results was based on a sequence of the pertussis toxin promoter region. Detection of B. parapertussis was based on the amplification of a section of the IS1001 insertion sequence. An internal control was included. Data were available for the period 28 November 2000 to 9 July 2003. In this period, 3096 patients were examined for infection with B. pertussis and B. parapertussis by culture and PCR on the same day. B. pertussis was found in 496 (16 %) patients; 208 (42 %) were diagnosed by PCR alone whereas 17 (3 %) were diagnosed by culture alone. B. parapertussis was found in 64 (2 %) patients. The sensitivity of the PCR was 97 % and of culture 58 %. The specificity of PCR was 93 % when regarding culture as 100 % sensitive. There was a significant relationship between laboratory method and age, as the superiority of PCR was most marked in the age group 0.5-3 years. The PCR assay proved highly sensitive for the diagnosis of pertussis. The specificity estimate of the PCR assay suffers from the influence of a gold-standard method with a low sensitivity. The PCR assay is considered highly specific due to the amplification of two different sequences in two separate assays. (+info)
Strain-dependent role of BrkA during Bordetella pertussis infection of the murine respiratory tract.
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Bordetella pertussis, the causative agent of whooping cough, expresses many virulence factors believed to be involved in infection and disease progression. While these factors as a group are required for infection, deletion of individual virulence factor genes generally has limited effects on the ability of B. pertussis to efficiently infect the respiratory tract of mice, suggesting they may perform noncritical or redundant functions. We have recently observed that a B. pertussis strain, putatively with a mutation of a single gene, brkA, results in a severe defect in vivo. Although BrkA has been shown to be required for B. pertussis to resist complement-mediated killing in vitro, the relevance of these findings to the in vivo role of BrkA during infection has not been examined. Transducing this mutation into multiple wild-type B. pertussis strains allowed us to confirm the in vitro phenotype of reduced resistance to serum complement. All DeltabrkA mutants were increased in their sensitivity to complement in vitro, both in the presence and absence of antibodies. However, these strains differed substantially in their phenotypes in vivo. DeltabrkA mutants of recent clinical isolates were indistinguishable from wild-type strains in their efficient infection of respiratory organs, suggesting that the function of BrkA in these strains is noncritical or redundant. In contrast, multiple DeltabrkA strains derived from Tohama I were severely defective during the first week postinoculation compared to their wild-type parent. This defect was present even in complement-deficient mice, revealing a complement-independent phenotype for the DeltabrkA mutant in respiratory tract infection. (+info)
Toll-like receptor 4-dependent early elicited tumor necrosis factor alpha expression is critical for innate host defense against Bordetella bronchiseptica.
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Toll-like receptor 4 (TLR4) mediates the response to lipopolysaccharide, and its activation induces the expression of a large number of inflammatory genes, many of which are also induced by other pathogen-associated molecular patterns. Interestingly, the subset of genes that are dependent on TLR4 for optimal expression during gram-negative bacterial infection has not been determined. We have previously shown that TLR4-deficient mice rapidly develop acute pneumonia after inoculation with Bordetella bronchiseptica, suggesting that TLR4 is required for expression of early elicited gene products in this model. Microarray analysis with macrophages derived from wild-type and TLR4-deficient mice was used to identify genes whose expression, within 1 h of bacterial exposure, is dependent on TLR4. The results of this investigation suggest that TLR4 is not required for the majority of the transcriptional response to B. bronchiseptica. However, early tumor necrosis factor alpha (TNF-alpha) mRNA expression is primarily dependent on TLR4 and in vitro and in vivo protein levels substantiate this finding. TLR4-deficient mice and TNF-alpha-/- mice are similarly susceptible to infection with relatively low doses of B. bronchiseptica and in vivo neutralization studies indicate that it is the TLR4-dependent early elicited TNF-alpha response that is critical for preventing severe pneumonia and limiting bacterial growth. These results suggest that one critical role for TLR4 is the generation of a robust but transient TNF-alpha response that is critical to innate host defense during acute gram-negative respiratory infection. (+info)
Antimicrobial susceptibility of Bordetella bronchiseptica isolates from porcine respiratory tract infections.
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MICs for 349 Bordetella bronchiseptica isolates from respiratory tract infections of swine were determined by broth microdilution. The lowest MIC at which 90% of isolates tested are inhibited (MIC90) was that of tetracycline and enrofloxacin (0.5 microg/ml), whereas the highest MIC90s were those of tilmicosin and cephalothin (32 microg/ml) as well as streptomycin (256 microg/ml). (+info)
Role of Bordetella bronchiseptica adenylate cyclase in nasal colonization and in development of local and systemic immune responses in piglets.
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Two Bordetella bronchiseptica mutants, lacking the adenylate cyclase (Cya) or both Cya and pertactin (Prn), were compared with their parental strain NL1013 in their abilities to colonize the nose of neonate piglets and to induce local and systemic antibody responses against filamentous hemagglutinin (FHA) after intranasal (i.n.) inoculation. The number of bacteria recovered and the duration of infection in the nasal secretions were greater for the wild-type parent strain than for the Cya-deficient mutant, indicating that Cya plays an important role during B. bronchiseptica colonization of the nasal cavity. The double mutant did not colonize the nasal cavity and was less able to adhere to epithelial cells in vitro than the other two strains, supporting the hypothesis that Prn plays a major role in cell adhesion. In piglets inoculated with the wild type strain, anti-FHA IgM was found in the nasal secretions one week after inoculation, followed two weeks later by anti-FHA IgA; their presence was concomitant with decreases in bacterial counts. Anti-FHA IgG appeared at six weeks after infection in the serum. In contrast, i.n. inoculation with either mutant failed to induce a nasal secretory antibody response but did induce an earlier and higher IgM response in the serum than inoculation with the wild type strain. However, only the Cya-deficient mutant was able to prime the piglets for the development of a secondary nasal IgM and serum IgG response to FHA after intranasal inoculation with the wild type B. bronchiseptica. (+info)