scholarly journals Pertussis Toxin and Adenylate Cyclase Toxin Provide a One-Two Punch for Establishment of Bordetella pertussis Infection of the Respiratory Tract

2005 ◽  
Vol 73 (5) ◽  
pp. 2698-2703 ◽  
Author(s):  
Nicholas H. Carbonetti ◽  
Galina V. Artamonova ◽  
Charlotte Andreasen ◽  
Nicholas Bushar
Keyword(s):  
Adenylate Cyclase ◽  
Respiratory Tract ◽  
Pertussis Toxin ◽  
Bordetella Pertussis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Infection Model ◽  
Wild Type ◽  
Adenylate Cyclase Toxin ◽  
Tract Infections

ABSTRACT Previously we found that pertussis toxin (PT), an exotoxin virulence factor produced by Bordetella pertussis, plays an important early role in colonization of the respiratory tract by this pathogen, using a mouse intranasal infection model. In this study, we examined the early role played by another exotoxin produced by this pathogen, adenylate cyclase toxin (ACT). By comparing a wild-type strain to a mutant strain (ΔCYA) with an in-frame deletion of the cyaA gene encoding ACT, we found that the lack of ACT confers a significant peak (day 7) colonization defect (1 to 2 log10). In mixed-infection experiments, the ΔCYA strain was significantly outcompeted by the wild-type strain, and intranasal administration of purified ACT did not increase colonization by ΔCYA. These data suggest that ACT benefits the bacterial cells that produce it and, unlike PT, does not act as a soluble factor benefiting the entire infecting bacterial population. Comparison of lower respiratory tract infections over the first 4 days after inoculation revealed that the colonization defect of the PT deletion strain was apparent earlier than that of ΔCYA, suggesting that PT plays an earlier role than ACT in the establishment of B. pertussis infection. Examination of cells in the bronchoalveolar lavage fluid of infected mice revealed that, unlike PT, ACT does not appear to inhibit neutrophil influx to the respiratory tract early after infection but may combat neutrophil activity once influx has occurred.

scholarly journals Bordetella pertussis Virulence Factors Affect Phagocytosis by Human Neutrophils

2000 ◽  
Vol 68 (3) ◽  
pp. 1735-1739 ◽  
Author(s):  
Christine L. Weingart ◽  
Alison A. Weiss
Keyword(s):  
Adenylate Cyclase ◽  
Virulence Factors ◽  
Pertussis Toxin ◽  
Bordetella Pertussis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Human Neutrophils ◽  
Wild Type ◽  
Dermonecrotic Toxin ◽  
Adenylate Cyclase Toxin

ABSTRACT The interaction between human neutrophils and wild-typeBordetella pertussis or mutants expressing altered lipopolysaccharide or lacking virulence factors—pertussis toxin, adenylate cyclase toxin, dermonecrotic toxin, filamentous hemagglutinin (FHA), pertactin, or BrkA—was examined. In the absence of antibodies, the wild-type strain and the mutants, with the exception of mutants lacking FHA, attached efficiently to neutrophils. The addition of opsonizing antibodies caused a significant reduction (approximately 50%) in attachment of the wild-type strain and most of the mutants expressing FHA, suggesting that bacterium-mediated attachment is more efficient than Fc-mediated attachment. Phagocytosis was also examined. In the absence of antibodies, about 12% of the wild-type bacteria were phagocytosed. Opsonization caused a statistically significant reduction in phagocytosis (to 3%), possibly a consequence of reduced attachment. Phagocytosis of most of the mutants was similar to that of the wild type, with the exception of the mutants lacking adenylate cyclase toxin. About 70% of the adenylate cyclase toxin mutants were phagocytosed, but only in the presence of opsonizing antibody, suggesting that Fc receptor-mediated signaling may be needed for phagocytosis. These studies indicate that FHA mediates attachment ofB. pertussis to neutrophils, but adenylate cyclase toxin blocks phagocytosis.

scholarly journals Pertussis Toxin Plays an Early Role in Respiratory Tract Colonization by Bordetella pertussis

2003 ◽  
Vol 71 (11) ◽  
pp. 6358-6366 ◽  
Author(s):  
Nicholas H. Carbonetti ◽  
Galina V. Artamonova ◽  
R. Michael Mays ◽  
Zoe E. V. Worthington
Keyword(s):  
Respiratory Tract ◽  
Pertussis Toxin ◽  
Bordetella Pertussis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Saline Control ◽  
Control Analysis ◽  
Wild Type ◽  
Respiratory Tract Colonization ◽  
Infection Experiments

ABSTRACT In this study, we sought to determine whether pertussis toxin (PT), an exotoxin virulence factor produced exclusively by Bordetella pertussis, is important for colonization of the respiratory tract by this pathogen by using a mouse intranasal infection model. By comparing a wild-type Tohama I strain to a mutant strain with an in-frame deletion of the ptx genes encoding PT (ΔPT), we found that the lack of PT confers a significant peak (day 7) colonization defect (1 to 2 log10 units) over a range of bacterial inoculum doses and that this defect was apparent within 1 to 2 days postinoculation. In mixed-strain infection experiments, the ΔPT strain showed no competitive disadvantage versus the wild-type strain and colonized at higher levels than in the single-strain infection experiments. To test the hypothesis that soluble PT produced by the wild-type strain in mixed infections enhanced respiratory tract colonization by ΔPT, we coadministered purified PT with the ΔPT inoculum and found that colonization was increased to wild-type levels. This effect was not observed when PT was coadministered via a systemic route. Intranasal administration of purified PT up to 14 days prior to inoculation with ΔPT significantly increased bacterial colonization, but PT administration 1 day after bacterial inoculation did not enhance colonization versus a phosphate-buffered saline control. Analysis of bronchoalveolar lavage fluid samples from mice infected with either wild-type or ΔPT strains at early times after infection revealed that neutrophil influx to the lungs 48 h postinfection was significantly greater in response to ΔPT infection, implicating neutrophil chemotaxis as a possible target of PT activity promoting B. pertussis colonization of the respiratory tract.

scholarly journals Neutralizing Antibodies to Adenylate Cyclase Toxin Promote Phagocytosis of Bordetella pertussis by Human Neutrophils

2000 ◽  
Vol 68 (12) ◽  
pp. 7152-7155 ◽  
Author(s):  
Christine L. Weingart ◽  
Paula S. Mobberley-Schuman ◽  
Erik L. Hewlett ◽  
Mary C. Gray ◽  
Alison A. Weiss
Keyword(s):  
Monoclonal Antibodies ◽  
Adenylate Cyclase ◽  
Bordetella Pertussis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Immune Serum ◽  
Human Neutrophils ◽  
Wild Type ◽  
Human Immune ◽  
Adenylate Cyclase Toxin

ABSTRACT A previous study showed that opsonization with human immune serum could either promote or antagonize phagocytosis of Bordetella pertussis by human neutrophils depending on whether the bacteria expressed adenylate cyclase toxin. Opsonization of the wild-type strain inhibited phagocytosis relative to unopsonized controls. In contrast, mutants lacking adenylate cyclase toxin were efficiently phagocytosed when opsonized with human immune serum. In this study, we examined opsonization in the presence or absence of monoclonal antibodies to adenylate cyclase toxin. Addition of neutralizing monoclonal antibodies to adenylate cyclase toxin converted a serum that previously inhibited both attachment and phagocytosis of the wild-type strain to one that increased both attachment and phagocytosis compared to the no-serum control. Monoclonal antibodies that recognize the adenylate cyclase toxin but fail to neutralize activity were without effect. These results suggest that adenylate cyclase toxin inhibits both Fc receptor-mediated attachment and phagocytosis of B. pertussis by neutrophils.

scholarly journals Probing the Function of Bordetella bronchiseptica Adenylate Cyclase Toxin by Manipulating Host Immunity

1999 ◽  
Vol 67 (3) ◽  
pp. 1493-1500 ◽  
Author(s):  
Eric T. Harvill ◽  
Peggy A. Cotter ◽  
Ming Huam Yuk ◽  
Jeff F. Miller
Keyword(s):  
Adenylate Cyclase ◽  
Type Strain ◽  
Low Dose ◽  
Wild Type Strain ◽  
Bordetella Bronchiseptica ◽  
Polymorphonuclear Neutrophil ◽  
Wild Type ◽  
Phagocytic Cells ◽  
Adenylate Cyclase Toxin ◽  
Rag 1

ABSTRACT We have examined the role of adenylate cyclase-hemolysin (CyaA) by constructing an in-frame deletion in the Bordetella bronchiseptica cyaA structural gene and comparing wild-type andcyaA deletion strains in natural host infection models. Both the wild-type strain RB50 and its adenylate cyclase toxin deletion (ΔcyaA) derivative efficiently establish persistent infections in rabbits, rats, and mice following low-dose inoculation. In contrast, an inoculation protocol that seeds the lower respiratory tract revealed significant differences in bacterial numbers and in polymorphonuclear neutrophil recruitment in the lungs from days 5 to 12 postinoculation. We next explored the effects of disarming specific aspects of the immune system on the relative phenotypes of wild-type and ΔcyaA bacteria. SCID, SCID-beige, or RAG-1−/− mice succumbed to lethal systemic infection following high- or low-dose intranasal inoculation with the wild-type strain but not the ΔcyaA mutant. Mice rendered neutropenic by treatment with cyclophosphamide or by knockout mutation in the granulocyte colony-stimulating factor locus were highly susceptible to lethal infection by either wild-type or ΔcyaA strains. These results reveal the significant role played by neutrophils early in B. bronchiseptica infection and by acquired immunity at later time points and suggest that phagocytic cells are a primary in vivo target of theBordetella adenylate cyclase toxin.

scholarly journals In VivoEfficacy of Human Simulated Regimens of Carbapenems and Comparator Agents against NDM-1-Producing Enterobacteriaceae

2013 ◽  
Vol 58 (3) ◽  
pp. 1671-1677 ◽  
Author(s):  
Dora E. Wiskirchen ◽  
Patrice Nordmann ◽  
Jared L. Crandon ◽  
David P. Nicolau
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Similar Efficacy ◽  
Infection Model ◽  
High Dose ◽  
Wild Type ◽  
Prolonged Infusion ◽  
Content Type

ABSTRACTDoripenem and ertapenem have demonstrated efficacy against several NDM-1-producing isolatesin vivo, despite having high MICs. In this study, we sought to further characterize the efficacy profiles of humanized regimens of standard (500 mg given every 8 h) and high-dose, prolonged infusion of doripenem (2 g given every 8 h, 4-h infusion) and 1 g of ertapenem given intravenously every 24 h and the comparator regimens of ceftazidime at 2 g given every 8 h (2-h infusion), levofloxacin at 500 mg every 24 h, and aztreonam at 2 g every 6 h (1-h infusion) against a wider range of isolates in a murine thigh infection model. An isogenic wild-type strain and NDM-1-producingKlebsiella pneumoniaeand eight clinical NDM-1-producing members of the familyEnterobacteriaceaewere tested in immunocompetent- and neutropenic-mouse models. The wild-type strain was susceptible to all of the agents, while the isogenic NDM-1-producing strain was resistant to ceftazidime, doripenem, and ertapenem. Clinical NDM-1-producing strains were resistant to nearly all five of the agents (two were susceptible to levofloxacin). In immunocompetent mice, all of the agents produced ≥1-log10CFU reductions of the isogenic wild-type and NDM-1-producing strains after 24 h. Minimal efficacy of ceftazidime, aztreonam, and levofloxacin against the clinical NDM-1-producing strains was observed. However, despitein vitroresistance, ≥1-log10CFU reductions of six of eight clinical strains were achieved with high-dose, prolonged infusion of doripenem and ertapenem. Slight enhancements of doripenem activity over the standard doses were obtained with high-dose, prolonged infusion for three of the four isolates tested. Similar efficacy observations were noted in neutropenic mice. These data suggest that carbapenems are a viable treatment option for infections caused by NDM-1-producingEnterobacteriaceae.

scholarly journals Evaluation of the Role of the Bvg Intermediate Phase in Bordetella pertussis during Experimental Respiratory Infection

2005 ◽  
Vol 73 (2) ◽  
pp. 748-760 ◽  
Author(s):  
Nuria Vergara-Irigaray ◽  
Alberto Chávarri-Martínez ◽  
Juan Rodríguez-Cuesta ◽  
Jeff F. Miller ◽  
Peggy A. Cotter ◽  
...  
Keyword(s):  
Respiratory Tract ◽  
Bordetella Pertussis ◽  
Wild Type Strain ◽  
Intermediate Phase ◽  
Transcriptional Level ◽  
Wild Type ◽  
Environmental Signals ◽  
Time Point

ABSTRACT The BvgAS system of Bordetella pertussis was traditionally considered to mediate a transition between two phenotypic phases (Bvg+ and Bvg−) in response to environmental signals. We characterized a third state, the intermediate (Bvgi) phase, which can be induced by introducing a 1-bp substitution into bvgS (the bvgS-I1 mutation) or by growing B. pertussis under conditions intermediate between those leading to the Bvg+ and Bvg− phases. Like B. bronchiseptica, B. pertussis displays in its Bvgi phase a characteristic colony morphology and hemolytic activity and expresses a Bvgi-phase-specific polypeptide called BipA, whose synthesis is regulated by bvgAS at the transcriptional level. Based on our results, we hypothesize that the Bvgi phase of B. pertussis may be involved in facilitating transmission between hosts. Thus, a B. pertussis mutant carrying the bvgS-I1 mutation (GMT1i) persisted at wild-type levels only in the upper murine respiratory tract. Interestingly, a bipA deletion derivative of GMT1i displayed a reduced ability to colonize the nasal cavity of mice compared with GMT1i. However, in experimental mixed infections GMT1i expressing the Bvgi phase could establish an initial colonization in the nose and trachea of mice as efficiently as GMT1, but the wild-type strain outcompeted GMT1i at a later time point at all sites of the respiratory tract, suggesting that the Bvgi phase does not serve as a phenotypic phase specialized in colonization. Finally, even though B. pertussis expresses in vitro the Bvgi phase at the human nasal temperature, anti-BipA antibodies were undetectable in a large collection of sera from pertussis patients.

scholarly journals Colonization of the Respiratory Tract by a Virulent Strain of Avian Escherichia coli Requires Carriage of a Conjugative Plasmid

2000 ◽  
Vol 68 (3) ◽  
pp. 1535-1541 ◽  
Author(s):  
C. A. Ginns ◽  
M. L. Benham ◽  
L. M. Adams ◽  
K. G. Whithear ◽  
K. A. Bettelheim ◽  
...  
Keyword(s):  
Respiratory Tract ◽  
Type Strain ◽  
Broiler Chickens ◽  
Wild Type Strain ◽  
Virulent Strain ◽  
Conjugative Plasmid ◽  
Virulence Plasmid ◽  
Wild Type ◽  
E Coli ◽  
Aerosol Exposure

ABSTRACT The E3 strain of E. coli was isolated in an outbreak of respiratory disease in broiler chickens, and experimental aerosol exposure of chickens to this strain induced disease similar to that seen in the field. In order to establish whether the virulent phenotype of this strain was associated with carriage of particular plasmids, four plasmid-cured derivatives, each lacking two or more of the plasmids carried by the wild-type strain, were assessed for virulence. Virulence was found to be associated with one large plasmid, pVM01. Plasmid pVM01 was marked by introduction of the transposon TnphoA, carrying kanamycin resistance, and was then cloned by transformation of E. coli strain DH5α. The cloned plasmid was then reintroduced by conjugation into an avirulent plasmid-cured derivative of strain E3 which lacked pVM01. The conjugant was shown to be as virulent as the wild-type strain E3, establishing that this plasmid is required for virulence following aerosol exposure. This virulence plasmid conferred expression of a hydroxamate siderophore, but not colicins, on both strain E3 and strain DH5α. Carriage of this plasmid was required for strain E3 to colonize the respiratory tracts of chickens but was not necessary for colonization of the gastrointestinal tract. However, the virulence plasmid did not confer virulence, or the capacity to colonize the respiratory tract, on strain DH5α. Thus, these studies have established that infection of chickens with E. coli strain E3 by the respiratory route is dependent on carriage of a conjugative virulence plasmid, which confers the capacity to colonize specifically the respiratory tract and which also carries genes for expression of a hydroxymate siderophore. These findings will facilitate identification of the specific genes required for virulence in these pathogens.

scholarly journals Leptospira interrogans lpxDHomologue Is Required for Thermal Acclimatization and Virulence

2015 ◽  
Vol 83 (11) ◽  
pp. 4314-4321 ◽  
Author(s):  
Azad Eshghi ◽  
Jeremy Henderson ◽  
M. Stephen Trent ◽  
Mathieu Picardeau
Keyword(s):  
Outer Membrane ◽  
Type Strain ◽  
Lipid A ◽  
Wild Type Strain ◽  
Infection Model ◽  
Leptospira Interrogans ◽  
Wild Type ◽  
Content Type ◽  
Physiological Temperature ◽  
Animal Infection

ABSTRACTLeptospirosis is an emerging disease with an annual occurrence of over 1 million human cases worldwide. PathogenicLeptospirabacteria are maintained in zoonotic cycles involving a diverse array of mammals, with the capacity to survive outside the host in aquatic environments. Survival in the diverse environments encountered byLeptospiralikely requires various adaptive mechanisms. Little is known aboutLeptospiraouter membrane modification systems, which may contribute to the capacity of these bacteria to successfully inhabit and colonize diverse environments and animal hosts.Leptospirabacteria carry two genes annotated as UDP-3-O-[3-hydroxymyristoyl] glucosamineN-acyltransferase genes (la0512 and la4326 [lpxD1andlpxD2]) that in other bacteria are involved in the early steps of biosynthesis of lipid A, the membrane lipid anchor of lipopolysaccharide. Inactivation of only one of these genes, la0512/lpxD1, imparted sensitivity to the host physiological temperature (37°C) and rendered the bacteria avirulent in an animal infection model. Polymyxin B sensitivity assays revealed compromised outer membrane integrity in thelpxD1mutant at host physiological temperature, but structural analysis of lipid A in the mutant revealed only minor changes in the lipid A moiety compared to that found in the wild-type strain. In accordance with this, anin transcomplementation restored the phenotypes to a level comparable to that of the wild-type strain. These results suggest that the gene annotated aslpxD1inLeptospira interrogansplays an important role in temperature adaptation and virulence in the animal infection model.

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