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  • American Society for Microbiology  (22)
  • 1
    Online Resource
    Online Resource
    Host Physiologic Changes Induced by Influenza A Virus Lead to Staphylococcus aureus Biofilm Dispersion and Transition from Asymptomatic Colonization to Invasive Disease
    American Society for Microbiology ; 2016
    In:  mBio Vol. 7, No. 4 ( 2016-09-07)
    Details
    In: mBio, American Society for Microbiology, Vol. 7, No. 4 ( 2016-09-07)
    Abstract: In this study, we have determined that host physiologic changes related to influenza A virus infection causes S. aureus to disperse from a biofilm state. Additionally, we report that these same host physiologic changes promote S. aureus dissemination from the nasal tissue to the lungs in an animal model. Furthermore, this study identifies important aspects involved in the transition of S. aureus from asymptomatic colonization to pneumonia.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.01235-16
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2016
    detail.hit.zdb_id: 2557172-2
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  • 2
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    Online Resource
    Rat Pneumonia and Soft-Tissue Infection Models for the Study of Acinetobacter baumannii Biology
    American Society for Microbiology ; 2008
    In:  Infection and Immunity Vol. 76, No. 8 ( 2008-08), p. 3577-3586
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 76, No. 8 ( 2008-08), p. 3577-3586
    Abstract: Acinetobacter baumannii is a bacterial pathogen of increasing medical importance. Little is known about its mechanisms of pathogenesis, and safe reliable agents with predictable activity against A. baumannii are presently nonexistent. The availability of relevant animal infection models will facilitate the study of Acinetobacter biology. In this report we tested the hypothesis that the rat pneumonia and soft-tissue infection models that our laboratory had previously used for studies of extraintestinal pathogenic Escherichia coli were clinically relevant for A. baumannii . Advantages of these models over previously described models were that the animals were not rendered neutropenic and they did not receive porcine mucin with bacterial challenge. Using the A. baumannii model pathogen 307-0294 as the challenge pathogen, the pneumonia model demonstrated all of the features of infection that are critical for a clinically relevant model: namely, bacterial growth/clearance, an ensuing host inflammatory response, acute lung injury, and, following progressive bacterial proliferation, death due to respiratory failure. We were also able to demonstrate growth of 307-0294 in the soft-tissue infection model. Next we tested the hypothesis that the soft-tissue infection model could be used to discriminate between the inherent differences in virulence of various A. baumannii clinical isolates. The ability of A. baumannii to grow and/or be cleared in this model was dependent on the challenge strain. We also hypothesized that complement is an important host factor in protecting against A. baumannii infection in vivo. In support of this hypothesis was the observation that the serum sensitivity of various A. baumannii clinical isolates in vitro roughly paralleled their growth/clearance in the soft-tissue infection model in vivo. Lastly we hypothesized that the soft-tissue infection model would serve as an efficient screening mechanism for identifying gene essentiality for drug discovery. Random mutants of 307-0294 were initially screened for lack of growth in human ascites in vitro. Selected mutants were subsequently used for challenge in the soft-tissue infection model to determine if the disrupted gene was essential for growth in vivo. Using this approach, we have been able to successfully identify a number of genes essential for the growth of 307-0294 in vivo. In summary, these models are clinically relevant and can be used to study the innate virulence of various Acinetobacter clinical isolates and to assess potential virulence factors, vaccine candidates, and drug targets in vivo and can be used for pharmacokinetic and chemotherapeutic investigations.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00269-08
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2008
    detail.hit.zdb_id: 1483247-1
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  • 3
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    Online Resource
    Identification and Characterization of a Glycosyltransferase Involved in Acinetobacter baumannii Lipopolysaccharide Core Biosynthesis
    American Society for Microbiology ; 2010
    In:  Infection and Immunity Vol. 78, No. 5 ( 2010-05), p. 2017-2023
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 78, No. 5 ( 2010-05), p. 2017-2023
    Abstract: Although Acinetobacter baumannii has emerged as a significant cause of nosocomial infections worldwide, there have been few investigations describing the factors important for A. baumannii persistence and pathogenesis. This paper describes the first reported identification of a glycosyltransferase, LpsB, involved in lipopolysaccharide (LPS) biosynthesis in A. baumannii . Mutational, structural, and complementation analyses indicated that LpsB is a core oligosaccharide glycosyl transferase. Using a genetic approach, lpsB was compared with the lpsB homologues of several A. baumannii strains. These analyses indicated that LpsB is highly conserved among A. baumannii isolates. Furthermore, we developed a monoclonal antibody, monoclonal antibody 13C11, which reacts to an LPS core epitope expressed by approximately one-third of the A. baumannii clinical isolates evaluated to date. Previous studies describing the heterogeneity of A. baumannii LPS were limited primarily to structural analyses; therefore, studies evaluating the correlation between these surface glycolipids and pathogenesis were warranted. Our data from an evaluation of LpsB mutant 307::TN17, which expresses a deeply truncated LPS glycoform consisting of only two 3-deoxy- d -manno-octulosonic acid residues and lipid A, suggest that A. baumannii LPS is important for resistance to normal human serum and confers a competitive advantage for survival in vivo . These results have important implications for the role of LPS in A. baumannii infections.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00016-10
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2010
    detail.hit.zdb_id: 1483247-1
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  • 4
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    Online Resource
    Contribution of Moraxella catarrhalis Type IV Pili to Nasopharyngeal Colonization and Biofilm Formation
    American Society for Microbiology ; 2007
    In:  Infection and Immunity Vol. 75, No. 12 ( 2007-12), p. 5559-5564
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 75, No. 12 ( 2007-12), p. 5559-5564
    Abstract: Moraxella catarrhalis is a gram-negative mucosal pathogen of the human respiratory tract. Although little information is available regarding the initial steps of M. catarrhalis pathogenesis, this organism must be able to colonize the human mucosal surface in order to initiate an infection. Type IV pili (TFP), filamentous surface appendages primarily comprised of a single protein subunit termed pilin, play a crucial role in the initiation of disease by a wide range of bacteria. We previously identified the genes that encode the major proteins involved in the biosynthesis of M. catarrhalis TFP and determined that the TFP expressed by this organism are highly conserved and essential for natural transformation. We extended this initial study by investigating the contribution of TFP to the early stages of M. catarrhalis colonization. TFP-deficient M. catarrhalis bacteria exhibit diminished adherence to eukaryotic cells in vitro. Additionally, our studies demonstrate that M. catarrhalis cells form a mature biofilm in continuous-flow chambers and that biofilm formation is enhanced by TFP expression. The potential role of TFP in colonization by M. catarrhalis was further investigated using in vivo studies comparing the abilities of wild-type M. catarrhalis and an isogenic TFP mutant to colonize the nasopharynx of the chinchilla. These results suggest that the expression of TFP contributes to mucosal airway colonization. Furthermore, these data indicate that the chinchilla model of nasopharyngeal colonization provides an effective animal system for studying the early steps of M. catarrhalis pathogenesis.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00946-07
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2007
    detail.hit.zdb_id: 1483247-1
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  • 5
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    Construction and Characterization of Moraxella catarrhalis Mutants Defective in Expression of Transferrin Receptors
    American Society for Microbiology ; 1999
    In:  Infection and Immunity Vol. 67, No. 11 ( 1999-11), p. 5815-5819
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 67, No. 11 ( 1999-11), p. 5815-5819
    Abstract: We have previously reported the construction of an isogenic mutant defective in expression of OmpB1, the TbpB homologue, in Moraxella catarrhalis 7169. In this report, we have extended these studies by constructing and characterizing two new isogenic mutants in this clinical isolate. One mutant is defective in expression of TbpA, and the other mutant is defective in expression of both TbpA and TbpB. These isogenic mutants were confirmed by using PCR analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and sequencing. In vitro growth studies, comparing all three mutants, demonstrated that the tbpA mutant and the tbpAB mutant were severely limited in their ability to grow with human holotransferrin as the sole source of iron. In contrast, the ompB1 ( tbpB ) mutant was capable of utilizing iron from human transferrin, although not to the extent of the parental strain. While affinity chromatography with human holotransferrin showed that each Tbp was capable of binding independently to transferrin, solid-phase transferrin binding studies using whole cells demonstrated that the tbpA mutant exhibited binding characteristics similar to those seen with the wild-type bacteria. However, the ompB1 ( tbpB ) mutant exhibited a diminished capacity for binding transferrin, and no binding was detected with the double mutant. These data suggest that the M. catarrhalis TbpA is necessary for the acquisition of iron from transferrin. In contrast, TbpB is not essential but may serve as a facilitory protein that functions to optimize this process. Together these mutants are essential to provide a more thorough understanding of iron acquisition mechanisms utilized by M. catarrhalis .
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.67.11.5815-5819.1999
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1999
    detail.hit.zdb_id: 1483247-1
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  • 6
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    Online Resource
    Identification and Characterization of an Acinetobacter baumannii Biofilm-Associated Protein
    American Society for Microbiology ; 2008
    In:  Journal of Bacteriology Vol. 190, No. 3 ( 2008-02), p. 1036-1044
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 190, No. 3 ( 2008-02), p. 1036-1044
    Abstract: We have identified a homologue to the staphylococcal biofilm-associated protein (Bap) in a bloodstream isolate of Acinetobacter baumannii . The fully sequenced open reading frame is 25,863 bp and encodes a protein with a predicted molecular mass of 854 kDa. Analysis of the nucleotide sequence reveals a repetitive structure consistent with bacterial cell surface adhesins. Bap-specific monoclonal antibody (MAb) 6E3 was generated to an epitope conserved among 41% of A. baumannii strains isolated during a recent outbreak in the U.S. military health care system. Flow cytometry confirms that the MAb 6E3 epitope is surface exposed. Random transposon mutagenesis was used to generate A. baumannii bap1302 ::EZ-Tn 5 , a mutant negative for surface reactivity to MAb 6E3 in which the transposon disrupts the coding sequence of bap . Time course confocal laser scanning microscopy and three-dimensional image analysis of actively growing biofilms demonstrates that this mutant is unable to sustain biofilm thickness and volume, suggesting a role for Bap in supporting the development of the mature biofilm structure. This is the first identification of a specific cell surface protein directly involved in biofilm formation by A. baumannii and suggests that Bap is involved in intercellular adhesion within the mature biofilm.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.01416-07
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2008
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 7
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    Online Resource
    Inactivation of the Moraxella catarrhalis Superoxide Dismutase SodA Induces Constitutive Expression of Iron-Repressible Outer Membrane Proteins
    American Society for Microbiology ; 2002
    In:  Infection and Immunity Vol. 70, No. 4 ( 2002-04), p. 1889-1895
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 70, No. 4 ( 2002-04), p. 1889-1895
    Abstract: Many pathogens produce one or more superoxide dismutases (SODs), enzymes involved in the detoxification of endogenous and exogenous reactive oxygen species that are encountered during the infection process. One detectable cytoplasmic SOD was identified in the human mucosal pathogen Moraxella catarrhalis , and the gene responsible for the SOD activity, sodA , was isolated from a recent pediatric clinical isolate (strain 7169). Sequence analysis of the cloned M. catarrhalis 7169 DNA fragment revealed an open reading frame of 618 bp encoding a polypeptide of 205 amino acids with 48 to 67% identity to known bacterial manganese-cofactored SODs. An isogenic M. catarrhalis sodA mutant was constructed in strain 7169 by allelic exchange. In contrast to the wild-type 7169, the 7169::sodK20 mutant was severely attenuated for aerobic growth, even in rich medium containing supplemental amino acids, and exhibited extreme sensitivity to the redox-active agent methyl viologen. The ability of recombinant SodA to rescue the aerobic growth defects of E. coli QC774, a sodA sodB -deficient mutant, demonstrated the functional expression of SOD activity by cloned M. catarrhalis sodA . Indirect SOD detection assays were used to visualize both native and recombinant SodA activity in bacterial lysates. This study demonstrates that M. catarrhalis SodA plays a critical role in the detoxification of endogenous, metabolically produced oxygen radicals. In addition, the outer membrane protein (OMP) profile of 7169::sodK20 was consistent with iron starvation in spite of growth under iron-replete conditions. This novel observation indicates that M. catarrhalis strains lacking SodA constitutively express immunogenic OMPs previously described as iron repressible, and this potentially attenuated mutant strain may be an attractive vaccine candidate.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.70.4.1889-1895.2002
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2002
    detail.hit.zdb_id: 1483247-1
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  • 8
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    Expression of Type IV Pili by Moraxella catarrhalis Is Essential for Natural Competence and Is Affected by Iron Limitation
    American Society for Microbiology ; 2004
    In:  Infection and Immunity Vol. 72, No. 11 ( 2004-11), p. 6262-6270
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 72, No. 11 ( 2004-11), p. 6262-6270
    Abstract: Type IV pili, filamentous surface appendages primarily composed of a single protein subunit termed pilin, play a crucial role in the initiation of disease by a wide range of pathogenic bacteria. Although previous electron microscopic studies suggested that pili might be present on the surface of Moraxella catarrhalis isolates, detailed molecular and phenotypic analyses of these structures have not been reported to date. We identified and cloned the M. catarrhalis genes encoding PilA, the major pilin subunit, PilQ, the outer membrane secretin through which the pilus filament is extruded, and PilT, the NTPase that mediates pilin disassembly and retraction. To initiate investigation of the role of this surface organelle in pathogenesis, isogenic pilA , pilT , and pilQ mutants were constructed in M. catarrhalis strain 7169. Comparative analyses of the wild-type 7169 strain and three isogenic pil mutants demonstrated that M. catarrhalis expresses type IV pili that are essential for natural genetic transformation. Our studies suggest type IV pilus production by M. catarrhalis is constitutive and ubiquitous, although pilin expression was demonstrated to be iron responsive and Fur regulated. These data indicate that additional studies aimed at elucidating the prevalence and role of type IV pili in the pathogenesis and host response to M. catarrhalis infections are warranted.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.72.11.6262-6270.2004
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2004
    detail.hit.zdb_id: 1483247-1
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  • 9
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    Identification of a 3-Deoxy- d - manno -Octulosonic Acid Biosynthetic Operon in Moraxella catarrhalis and Analysis of a KdsA-Deficient Isogenic Mutant
    American Society for Microbiology ; 2003
    In:  Infection and Immunity Vol. 71, No. 11 ( 2003-11), p. 6426-6434
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 71, No. 11 ( 2003-11), p. 6426-6434
    Abstract: Lipooligosaccharide (LOS), a predominant surface-exposed component of the outer membrane, has been implicated as a virulence factor in the pathogenesis of Moraxella catarrhalis infections. However, the critical steps involved in the biosynthesis and assembly of M. catarrhalis LOS currently remain undefined. In this study, we used random transposon mutagenesis to identify a 3-deoxy- d - manno -octulosonic acid (KDO) biosynthetic operon in M. catarrhalis with the gene order pyrG - kdsA - eno . The lipid A-KDO molecule serves as the acceptor onto which a variety of glycosyl transferases sequentially add the core and branch oligosaccharide extensions for the LOS molecule. KdsA, the KDO-8-phosphate synthase, catalyzes the first step of KDO biosynthesis and is an essential enzyme in gram-negative enteric bacteria for maintenance of bacterial viability. We report the construction of an isogenic M. catarrhalis kdsA mutant in strain 7169 by allelic exchange. Our data indicate that an LOS molecule consisting only of lipid A and lacking KDO glycosylation is sufficient to sustain M. catarrhalis survival in vitro. In addition, comparative growth and susceptibility assays were performed to assess the sensitivity of 7169kdsA11 compared to that of the parental strain. The results of these studies demonstrate that the native LOS molecule is an important factor in maintaining the integrity of the outer membrane and suggest that LOS is a critical component involved in the ability of M. catarrhalis to resist the bactericidal activity of human sera.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.71.11.6426-6434.2003
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2003
    detail.hit.zdb_id: 1483247-1
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  • 10
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    The K1 Capsular Polysaccharide from Acinetobacter baumannii Is a Potential Therapeutic Target via Passive Immunization
    American Society for Microbiology ; 2013
    In:  Infection and Immunity Vol. 81, No. 3 ( 2013-03), p. 915-922
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 81, No. 3 ( 2013-03), p. 915-922
    Abstract: The emergence of extremely resistant and panresistant Gram-negative bacilli, such as Acinetobacter baumannii , requires consideration of nonantimicrobial therapeutic approaches. The goal of this report was to evaluate the K1 capsular polysaccharide from A. baumannii as a passive immunization target. Its structure was determined by a combination of mass spectrometric and nuclear magnetic resonance (NMR) techniques. Molecular mimics that might raise the concern for autoimmune disease were not identified. Immunization of CD1 mice demonstrated that the K1 capsule is immunogenic. The monoclonal antibody (MAb) 13D6, which is directed against the K1 capsule from A. baumannii , was used to determine the seroprevalence of the K1 capsule in a collection of 100 A. baumannii strains. Thirteen percent of the A. baumannii isolates from this collection were seroreactive to MAb 13D6. Opsonization of K1-positive strains, but not K1-negative strains, with MAb 13D6 significantly increased neutrophil-mediated bactericidal activity in vitro ( P 〈 0.05). Lastly, treatment with MAb 13D6 3 and 24 h after bacterial challenge in a rat soft tissue infection model resulted in a significant decrease in the growth/survival of a K1-positive strain compared to that of a K1-negative strain or to treatment with a vehicle control ( P 〈 0.0001). These data support the proof of principle that the K1 capsule is a potential therapeutic target via passive immunization. Other serotypes require assessment, and pragmatic challenges exist, such as the need to serotype infecting strains and utilize serotype-specific therapy. Nonetheless, this approach may become an important therapeutic option with increasing antimicrobial resistance and a diminishing number of active antimicrobials.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.01184-12
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2013
    detail.hit.zdb_id: 1483247-1
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