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Articles 151 - 180 of 182

Full-Text Articles in Medicine and Health Sciences

Rhamnolipids Modulate Swarming Motility Patterns Of Pseudomonas Aeruginosa, Nicky C. Caiazza, Robert M. Q. Shanks, G. A. O'Toole Nov 2005

Rhamnolipids Modulate Swarming Motility Patterns Of Pseudomonas Aeruginosa, Nicky C. Caiazza, Robert M. Q. Shanks, G. A. O'Toole

Dartmouth Scholarship

Pseudomonas aeruginosa is capable of twitching, swimming, and swarming motility. The latter form of translocation occurs on semisolid surfaces, requires functional flagella and biosurfactant production, and results in complex motility patterns. From the point of inoculation, bacteria migrate as defined groups, referred to as tendrils, moving in a coordinated manner capable of sensing and responding to other groups of cells. We were able to show that P. aeruginosa produces extracellular factors capable of modulating tendril movement, and genetic analysis revealed that modulation of these movements was dependent on rhamnolipid biosynthesis. An rhlB mutant (deficient in mono- and dirhamnolipid production) and …

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Experimental Ocular Toxoplasmosis In Genetically Susceptible And Resistant Mice, Fangli Lu, Shiguang Huang, Mark S. Hu, Lloyd H. Kasper Aug 2005

Experimental Ocular Toxoplasmosis In Genetically Susceptible And Resistant Mice, Fangli Lu, Shiguang Huang, Mark S. Hu, Lloyd H. Kasper

Dartmouth Scholarship

Genetic factors determining the pathogenesis and course of ocular toxoplasmosis are poorly understood. In this study, we explored the development of experimental ocular pathogenesis in genetically dissimilar mice infected with either the RH strain, the PLK strain, or the immunodominant surface antigen 1 (SAG1 [P30])-deficient mutant of the RH strain of Toxoplasma gondii. At 11 days postinfection, ocular infection of C57BL/6 mice with all of the strains of parasites resulted in severe inflammatory lesions and high numbers of parasites in eye tissue; less severe ocular lesions at earlier histopathology and prolonged survival were observed in this mouse strain infected …

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Heparin Stimulates Staphylococcus Aureus Biofilm Formation, Robert M. Q. Shanks, Niles P. Donegan, Martha L. Graber, Sarah E. Buckingham, Michael Zegans, Ambrose Cheung, George A. O'Toole Aug 2005

Heparin Stimulates Staphylococcus Aureus Biofilm Formation, Robert M. Q. Shanks, Niles P. Donegan, Martha L. Graber, Sarah E. Buckingham, Michael Zegans, Ambrose Cheung, George A. O'Toole

Dartmouth Scholarship

Heparin, known for its anticoagulant activity, is commonly used in catheter locks. Staphylococcus aureus, a versatile human and animal pathogen, is commonly associated with catheter-related bloodstream infections and has evolved a number of mechanisms through which it adheres to biotic and abiotic surfaces. We demonstrate that heparin increased biofilm formation by several S. aureus strains. Surface coverage and the kinetics of biofilm formation were stimulated, but primary attachment to the surface was not affected. Heparin increased S. aureus cell-cell interactions in a protein synthesis-dependent manner. The addition of heparin rescued biofilm formation of hla, ica, and sarA …

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Tcpf Is A Soluble Colonization Factor And Protective Antigen Secreted By El Tor And Classical O1 And O139 Vibrio Cholerae Serogroups, Thomas J. Kirn, Ronald K. Taylor Aug 2005

Tcpf Is A Soluble Colonization Factor And Protective Antigen Secreted By El Tor And Classical O1 And O139 Vibrio Cholerae Serogroups, Thomas J. Kirn, Ronald K. Taylor

Dartmouth Scholarship

Vibrio cholerae causes diarrhea by colonizing the human small bowel and intoxicating epithelial cells. Colonization is a required step in pathogenesis, and strains defective for colonization are significantly attenuated. The best-characterized V. cholerae colonization factor is the toxin-coregulated pilus (TCP). It has been demonstrated that TCP is required for V. cholerae colonization in both humans and mice. TCP enhances bacterial interactions that allow microcolony formation and thereby promotes survival in the intestine. We have recently discovered that the TCP biogenesis apparatus also serves as a secretion system, mediating the terminal step in the extracellular secretion pathway of TcpF. TcpF was …

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Role Of The Distal Sara Promoters In Sara Expression In Staphylococcus Aureus, Ambrose L. Cheung, Adhar C. Manna Jul 2005

Role Of The Distal Sara Promoters In Sara Expression In Staphylococcus Aureus, Ambrose L. Cheung, Adhar C. Manna

Dartmouth Scholarship

The global regulatory locus sarA comprises a 375-bp open reading frame that is driven by three promoters, the proximal P1 and distal P3 and P2 promoters. We mutated the weaker P3 and P2 promoters to ascertain the effect of the change on SarA protein and target gene expression. Our results indicated that the solely active P1 promoter led to a lower SarA protein level, which has an effect on agr transcription and subsequently had corresponding effects on hla, sspA, and spa transcription, probably in both agr-independent and agr-dependent manners.

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Thymidine-Dependent Staphylococcus Aureus Small-Colony Variants Are Associated With Extensive Alterations In Regulator And Virulence Gene Expression Profiles, Barbara C. Kahl, Gunnar Belling, Petra Becker, Indranil Chatterjee, Katrin Wardecki, Karin Hilgert, Ambrose Cheung Jul 2005

Thymidine-Dependent Staphylococcus Aureus Small-Colony Variants Are Associated With Extensive Alterations In Regulator And Virulence Gene Expression Profiles, Barbara C. Kahl, Gunnar Belling, Petra Becker, Indranil Chatterjee, Katrin Wardecki, Karin Hilgert, Ambrose Cheung

Dartmouth Scholarship

Chronic airway infection is a hallmark of cystic fibrosis (CF) and many CF patients are infected persistently by Staphylococcus aureus. Thymidine-dependent trimethoprim-sulfamethoxazole (SXT)-resistant S. aureus small-colony variants (SCVs), often in combination with isogenic normal S. aureus phenotypes, are highly prevalent and persistent in airway secretions of CF patients due to long-term SXT therapy (B. Kahl, M. Herrmann, A. S. Everding, H. G. Koch, K. Becker, E. Harms, R. A. Proctor, and G.

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Identification Of A Tcpc-Tcpq Outer Membrane Complex Involved In The Biogenesis Of The Toxin-Coregulated Pilus Of Vibrio Cholerae, Niranjan Bose, Ronald K. Taylor Apr 2005

Identification Of A Tcpc-Tcpq Outer Membrane Complex Involved In The Biogenesis Of The Toxin-Coregulated Pilus Of Vibrio Cholerae, Niranjan Bose, Ronald K. Taylor

Dartmouth Scholarship

The toxin-coregulated pilus (TCP) of Vibrio cholerae and the soluble TcpF protein that is secreted via the TCP biogenesis apparatus are essential for intestinal colonization. The TCP biogenesis apparatus is composed of at least nine proteins but is largely uncharacterized. TcpC is an outer membrane lipoprotein required for TCP biogenesis that is a member of the secretin protein superfamily. In the present study, analysis of TcpC in a series of strains deficient in each of the TCP biogenesis proteins revealed that TcpC was absent specifically in a tcpQ mutant. TcpQ is a predicted periplasmic protein required for TCP biogenesis. Fractionation …

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Rat/Mgra, A Regulator Of Autolysis, Is A Regulator Of Virulence Genes In Staphylococcus Aureus, Susham Ingavale, Willem Van Wamel, Thanh T. Luong, Chia Y. Lee, Ambrose L. Cheung Mar 2005

Rat/Mgra, A Regulator Of Autolysis, Is A Regulator Of Virulence Genes In Staphylococcus Aureus, Susham Ingavale, Willem Van Wamel, Thanh T. Luong, Chia Y. Lee, Ambrose L. Cheung

Dartmouth Scholarship

We have previously identified mgrA (rat) as a regulator of autolysis in Staphylococcus aureus. Besides its effect on autolytic activity, we recently found alterations in the expression of regulator and target virulence genes in the mgrA mutant. Northern analysis and transcription fusion assays showed that inactivation of mgrA has led to the downregulation of RNAIII of agr and hla and upregulation of sarS and spa. Although both SarA and agr are activators of α-hemolysin and a repressors of protein A synthesis, we found that the transcription of sarA was not affected in the mgrA mutant and …

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Dynamic Changes In Mcl-1 Expression Regulate Macrophage Viability Or Commitment To Apoptosis During Bacterial Clearance, Helen M. Marriott, Colin D. Bingle, Robert C. Read, Karen E. Braley, Guido Kroemer, Paul G. Hellewell, Ruth W. Craig, Moira K.B. Whyte, David H. Dockrell Feb 2005

Dynamic Changes In Mcl-1 Expression Regulate Macrophage Viability Or Commitment To Apoptosis During Bacterial Clearance, Helen M. Marriott, Colin D. Bingle, Robert C. Read, Karen E. Braley, Guido Kroemer, Paul G. Hellewell, Ruth W. Craig, Moira K.B. Whyte, David H. Dockrell

Dartmouth Scholarship

Macrophages are critical effectors of bacterial clearance and must retain viability, despite exposure to toxic bacterial products, until key antimicrobial functions are performed. Subsequently, host-mediated macrophage apoptosis aids resolution of infection. The ability of macrophages to make this transition from resistance to susceptibility to apoptosis is important for effective host innate immune responses. We investigated the role of Mcl-1, an essential regulator of macrophage lifespan, in this switch from viability to apoptosis, using the model of pneumococcal-associated macrophage apoptosis. Upon exposure to pneumococci, macrophages initially upregulate Mcl-1 protein and maintain viability for up to 14 hours. Subsequently, macrophages reduce expression …

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Effect Of Dna Base Modification On Polymerase Chain Reaction Efficiency And Fidelity, Jan A. Sikorsky Jan 2005

Effect Of Dna Base Modification On Polymerase Chain Reaction Efficiency And Fidelity, Jan A. Sikorsky

Theses, Dissertations and Capstones

Polymerase stop assays, used to quantify DNA damage, assume single lesions are sufficient to block thermostable DNA polymerase progression. To explore this assumption, 90 base oligonucleotides containing normal or modified DNA bases were amplified using real-time PCR. Data implied that the PCR efficiency was influenced to differing degrees depending on which base lesion was present on the input oligonucleotide; specifically, while reactions with templates containing a single 8-oxo-7,8-dihydro-2í-deoxyguanosine (8-oxodG) were not noticeably altered, the presence of a single 8-oxo-7,8-dihydro-2í-deoxyadenosine, an abasic site, or a cis-syn thymidine dimer (TT dimer) dramatically delayed amplification. In addition, the presence of two tandem 8-oxodGs …

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Interleukin-17/Interleukin-17 Receptor-Mediated Signaling Is Important For Generation Of An Optimal Polymorphonuclear Response Against Toxoplasma Gondii Infection, Michelle N. Kelly, Jay K. Kolls, Kyle Happel, Joseph D. Schwartzman Jan 2005

Interleukin-17/Interleukin-17 Receptor-Mediated Signaling Is Important For Generation Of An Optimal Polymorphonuclear Response Against Toxoplasma Gondii Infection, Michelle N. Kelly, Jay K. Kolls, Kyle Happel, Joseph D. Schwartzman

Dartmouth Scholarship

We investigated the role of interleukin-17 (IL-17)/IL-17 receptor (IL-17R)-mediated signaling in the protective immunity against Toxoplasma gondii. IL-17R−/− mice developed a normal adaptive immunity against the parasite. However, increased mortality in the knockout animals can be attributed to a defect in the migration of polymorphonuclear leukocytes to infected sites during early infection.

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Role Of A Cytotoxic-T-Lymphocyte Epitope-Defined, Alternative Gag Open Reading Frame In The Pathogenesis Of A Murine Retrovirus-Induced Immunodeficiency Syndrome, Arti Gaur, William R. Green Nov 2004

Role Of A Cytotoxic-T-Lymphocyte Epitope-Defined, Alternative Gag Open Reading Frame In The Pathogenesis Of A Murine Retrovirus-Induced Immunodeficiency Syndrome, Arti Gaur, William R. Green

Dartmouth Scholarship

LP-BM5 murine leukemia virus-infected C57BL/6 mice develop profound immunodeficiency and B-cell lymphomas. The LP-BM5 complex contains a mixture of defective (BM5def) and replication-competent helper viruses among which BM5def is the primary causative agent of disease. The BM5def primary open reading frame (ORF1) encodes the single gag precursor protein (Pr60gag). Our lab has recently demonstrated that a novel immunodominant cytotoxic-T-lymphocyte (CTL) epitope (SYNTGRFPPL) is expressed from a +1-nucleotide translational open reading frame of BM5def during the course of normal retrovirus expression. The SYNTGRFPPL CTL epitope may be generated from either of two initiation methionines present, ORF2a or ORF2b, located …

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T-Cell Responses To The M3 Immune Evasion Protein Of Murid Gammaherpesvirus 68 Are Partially Protective And Induced With Lytic Antigen Kinetics, Joshua J. Obar, Douglas C. Donovan, Sarah G. Crist, Ondine Silvia, James P. Stewart, Edward J. Usherwood Oct 2004

T-Cell Responses To The M3 Immune Evasion Protein Of Murid Gammaherpesvirus 68 Are Partially Protective And Induced With Lytic Antigen Kinetics, Joshua J. Obar, Douglas C. Donovan, Sarah G. Crist, Ondine Silvia, James P. Stewart, Edward J. Usherwood

Dartmouth Scholarship

DNA vaccination with the M3 gene, encoding an immune evasion molecule expressed during both the acute lytic and persistent phases of murid gammaherpesvirus 68 infection, yielded a significantly lower titer of virus in the lung than controls. The protection seen was dependent on T cells, and we mapped an epitope recognized by CD8 T cells. The immune response to this epitope follows the same kinetics as lytic cycle antigens, despite the fact that this gene is expressed in both lytic and persistent stages of infection. This has important implications for our understanding of T-cell responses to putative latency-associated gammaherpesvirus proteins …

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The Major Subunit Of The Toxin-Coregulated Pilus Tcpa Induces Mucosal And Systemic Immunoglobulin A Immune Responses In Patients With Cholera Caused By Vibrio Cholerae O1 And O139, Muhammad Asaduzzaman, Edward T. Ryan, Manohar John, Long Hang, Ashraful I. Khan, A. S. G. Faruque, Ronald K. Taylor Aug 2004

The Major Subunit Of The Toxin-Coregulated Pilus Tcpa Induces Mucosal And Systemic Immunoglobulin A Immune Responses In Patients With Cholera Caused By Vibrio Cholerae O1 And O139, Muhammad Asaduzzaman, Edward T. Ryan, Manohar John, Long Hang, Ashraful I. Khan, A. S. G. Faruque, Ronald K. Taylor

Dartmouth Scholarship

Diarrhea caused by Vibrio cholerae is known to give long-lasting protection against subsequent life-threatening illness. The serum vibriocidal antibody response has been well studied and has been shown to correlate with protection. However, this systemic antibody response may be a surrogate marker for mucosal immune responses to key colonization factors of this organism, such as the toxin-coregulated pilus (TCP) and other factors. Information regarding immune responses to TCP, particularly mucosal immune responses, is lacking, particularly for patients infected with the El Tor biotype of V. cholerae O1 or V. cholerae O139 since highly purified TcpA from these strains has not …

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Synthetic Fragments Of Vibrio Cholerae O1 Inaba O-Specific Polysaccharide Bound To A Protein Carrier Are Immunogenic In Mice But Do Not Induce Protective Antibodies, Michael D. Meeks, Rina Saksena, Xingquan Ma, Terri K. Wade, Ronald K. Taylor, Pavol Kováč, William F. Wade Jul 2004

Synthetic Fragments Of Vibrio Cholerae O1 Inaba O-Specific Polysaccharide Bound To A Protein Carrier Are Immunogenic In Mice But Do Not Induce Protective Antibodies, Michael D. Meeks, Rina Saksena, Xingquan Ma, Terri K. Wade, Ronald K. Taylor, Pavol Kováč, William F. Wade

Dartmouth Scholarship

Development of Vibrio cholerae lipopolysaccharide (LPS) as a cholera vaccine immunogen is justified by the correlation of vibriocidal anti-LPS response with immunity. Two V. cholerae O1 LPS serotypes, Inaba and Ogawa, are associated with endemic and pandemic cholera. Both serotypes induce protective antibody following infection or vaccination. Structurally, the LPSs that define the serotypes are identical except for the terminal perosamine moiety, which has a methoxyl group at position 2 in Ogawa but a hydroxyl group in Inaba. The terminal sugar of the Ogawa LPS is a protective B-cell epitope. We chemically synthesized the terminal hexasaccharides of V. cholerae serotype …

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Isolation And Characterization Of A Generalized Transducing Phage For Pseudomonas Aeruginosa Strains Pao1 And Pa14, Jonathan M. Budzik, William A. Rosche, Arne Rietsch, George A. O'Toole May 2004

Isolation And Characterization Of A Generalized Transducing Phage For Pseudomonas Aeruginosa Strains Pao1 And Pa14, Jonathan M. Budzik, William A. Rosche, Arne Rietsch, George A. O'Toole

Dartmouth Scholarship

A temperate, type IV pilus-dependent, double-stranded DNA bacteriophage named DMS3 was isolated from a clinical strain of Pseudomonas aeruginosa. A clear-plaque variant of this bacteriophage was isolated. DMS3 is capable of mediating generalized transduction within and between P. aeruginosa strains PA14 and PAO1, thus providing a useful tool for the genetic analysis of P. aeruginosa.

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Effect Of Escherichia Coli And Lactobacillus Rhamnosus On Macrophage Inflammatory Protein 3Α, Tumor Necrosis Factor Alpha, And Transforming Growth Factor Β Release By Polarized Rat Uterine Epithelial Cells In Culture, M. A. Crane-Godreau, C. R. Wira Jan 2004

Effect Of Escherichia Coli And Lactobacillus Rhamnosus On Macrophage Inflammatory Protein 3Α, Tumor Necrosis Factor Alpha, And Transforming Growth Factor Β Release By Polarized Rat Uterine Epithelial Cells In Culture, M. A. Crane-Godreau, C. R. Wira

Dartmouth Scholarship

Entry of bacteria from the vagina into the uterus raises the question of uterine epithelial cell (UEC) signaling in response to the presence of bacteria. Our model system helps to define microbially elicited UEC basolateral cytokine release, important in regulating underlying stromal immune cell protection. UECs from adult rats were grown in cell culture inserts to establish a confluent polarized monolayer as was determined by transepithelial resistance (TER). Polarized epithelial cell cultures were treated apically with live or heat-killed Escherichia coli or Lactobacillus rhamnosus prior to collection of basolateral media after 24 h of incubation. Coculture of polarized UECs with …

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Cd40-Associated Traf 6 Signaling Is Required For Disease Induction In A Retrovirus-Induced Murine Immunodeficiency, Kathy A. Green, Cory L. Ahonen, W. James Cook, William R. Green Jan 2004

Cd40-Associated Traf 6 Signaling Is Required For Disease Induction In A Retrovirus-Induced Murine Immunodeficiency, Kathy A. Green, Cory L. Ahonen, W. James Cook, William R. Green

Dartmouth Scholarship

LP-BM5 retrovirus-infected C57BL/6 mice develop splenomegaly, lymphadenopathy, hypergammaglobulinemia, and immunodeficiency; thus, this disease has been named mouse AIDS. In this syndrome, CD154/CD40 interactions are required for but do not mediate disease by upregulation of CD80 or CD86. We report here that there is nonetheless a necessity for CD40 signaling competence, specifically an intact tumor necrosis factor receptor-associated factor 6 (TRAF 6) binding site.

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Sart Influences Sars Expression In Staphylococcus Aureus, Katherine A. Schmidt, Adhar C. Manna, Ambrose L. Cheung Sep 2003

Sart Influences Sars Expression In Staphylococcus Aureus, Katherine A. Schmidt, Adhar C. Manna, Ambrose L. Cheung

Dartmouth Scholarship

Staphylococcus aureus is a gram-positive pathogen that is capable of expressing a variety of virulence proteins in response to environmental signals. Virulence protein expression in S. aureus is controlled by a network of regulatory loci including sarA and agr. The sarA/agr network is associated with the expression of cell wall-associated adhesins during exponential growth and the expression of secreted enzymes and toxins in the transition to post-exponential growth. A number of sarA homologs, including sarT and sarS, have been identified in the S. aureus genome. Previous studies have shown that sarA influences expression of both sarT and sarS in the …

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Salicylic Acid Attenuates Virulence In Endovascular Infections By Targeting Global Regulatory Pathways In Staphylococcus Aureus, Leon Iri Kupferwasser, Michael R. Yeaman, Cynthia C. Nast, Deborah Kupferwasser, Yan-Qiong Xiong, Marco Palma, Ambrose L. Cheung, Arnold S. Bayer Jul 2003

Salicylic Acid Attenuates Virulence In Endovascular Infections By Targeting Global Regulatory Pathways In Staphylococcus Aureus, Leon Iri Kupferwasser, Michael R. Yeaman, Cynthia C. Nast, Deborah Kupferwasser, Yan-Qiong Xiong, Marco Palma, Ambrose L. Cheung, Arnold S. Bayer

Dartmouth Scholarship

Aspirin has been previously shown to reduce the in vivo virulence of Staphylococcus aureus in experimental endocarditis, through antiplatelet and antimicrobial mechanisms. In the present study, salicylic acid, the major in vivo metabolite of aspirin, mitigated two important virulence phenotypes in both clinical and laboratory S. aureus strains: α-hemolysin secretion and fibronectin binding in vitro. In addition, salicylic acid reduced the expression of the α-hemolysin gene promoter, hla, and the fibronectin gene promoter, fnbA. Transcriptional analysis, fluorometry, and flow cytometry revealed evidence of salicylic acid–mediated activation of the stress-response gene sigB. Expression of the sigB-repressible global …

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Use Of In Vivo-Induced Antigen Technology (Iviat) To Identify Genes Uniquely Expressed During Human Infection With Vibrio Cholerae, Long Hang, Manohar John, Muhammad Asaduzzaman, Emily A. Bridges, Cecily Vanderspurt, Thomas J. Kirn, Ronald K. Taylor Jul 2003

Use Of In Vivo-Induced Antigen Technology (Iviat) To Identify Genes Uniquely Expressed During Human Infection With Vibrio Cholerae, Long Hang, Manohar John, Muhammad Asaduzzaman, Emily A. Bridges, Cecily Vanderspurt, Thomas J. Kirn, Ronald K. Taylor

Dartmouth Scholarship

In vivo-induced antigen technology is a method to identify proteins expressed by pathogenic bacteria during human infection. Sera from 10 patients convalescing from cholera infection in Bangladesh were pooled, adsorbed against in vitro-grown El Tor Vibrio cholerae O1, and used to probe a genomic expression library in Escherichia coli constructed from El Tor V. cholerae O1 strain N16961. We identified 38 positive clones in the screen, encoding pili (PilA and TcpA), cell membrane proteins (PilQ, MshO, MshP, and CapK), methyl-accepting chemotaxis proteins, chemotaxis and motility proteins (CheA and CheR), a quorum-sensing protein (LuxP), and four hypothetical proteins. Analysis of immune …

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Saru, A Sara Homolog, Is Repressed By Sart And Regulates Virulence Genes In Staphylococcus Aureus, Adhar C. Manna, Ambrose L. Cheung Jan 2003

Saru, A Sara Homolog, Is Repressed By Sart And Regulates Virulence Genes In Staphylococcus Aureus, Adhar C. Manna, Ambrose L. Cheung

Dartmouth Scholarship

In searching the Staphylococcus aureus genome, we previously identified sarT, a homolog of sarA, which encodes a repressor for alpha-hemolysin synthesis. Adjacent but transcribed divergently to sarT is sarU, which encodes a 247-residue polypeptide, almost twice the length of SarA. Sequence alignment disclosed that SarU, like SarS, which is another SarA homolog, could be envisioned as a molecule with two halves, with each half being homologous to SarA. SarU, as a member of the SarA family proteins, disclosed conservation of basic residues within the helix-turn-helix motif and within the beta hairpin loop, two putative DNA binding domains within this protein …

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Mechanism Of Toxt-Dependent Transcriptional Activation At The Vibrio Cholerae Tcpa Promoter, Robin R. Hulbert, Ronald K. Taylor Oct 2002

Mechanism Of Toxt-Dependent Transcriptional Activation At The Vibrio Cholerae Tcpa Promoter, Robin R. Hulbert, Ronald K. Taylor

Dartmouth Scholarship

The AraC homolog ToxT coordinately regulates virulence gene expression in Vibrio cholerae. ToxT is required for transcriptional activation of the genes encoding cholera toxin and the toxin coregulated pilus, among others. In this work we focused on the interaction of ToxT with the tcpA promoter and investigated the mechanism of ToxT-dependent transcriptional activation at tcpA. Deletion analysis showed that a region from −95 to +2 was sufficient for ToxT binding and activation, both of which were simultaneously lost when the deletion was extended to −63. A collection of point mutations generated by error-prone PCR revealed two small regions required …

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Identification Of The Vibrio Cholerae Enterobactin Receptors Vcta And Irga: Irga Is Not Required For Virulence, Alexandra R. Mey, Elizabeth E. Wyckoff, Amanda G. Oglesby, Eva Rab, Ronald K. Taylor, Shelley M. Payne Jul 2002

Identification Of The Vibrio Cholerae Enterobactin Receptors Vcta And Irga: Irga Is Not Required For Virulence, Alexandra R. Mey, Elizabeth E. Wyckoff, Amanda G. Oglesby, Eva Rab, Ronald K. Taylor, Shelley M. Payne

Dartmouth Scholarship

The gram-negative enteric pathogen Vibrio cholerae requires iron for growth. V. cholerae has multiple iron acquisition systems, including utilization of heme and hemoglobin, synthesis and transport of the catechol siderophore vibriobactin, and transport of several siderophores that it does not itself make. One siderophore that V. cholerae transports, but does not make, is enterobactin. Enterobactin transport requires TonB and is independent of the vibriobactin receptor ViuA. In this study, two candidate enterobactin receptor genes, irgA (VC0475) and vctA (VCA0232), were identified by analysis of the V. cholerae genomic sequence. A single mutation in either of these genes did not significantly …

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Clumping Factor A Mediates Binding Of Staphylococcus Aureus To Human Platelets, Ian R. Siboo, Ambrose L. Cheung, Arnold S. Bayer, Paul M. Sullam May 2001

Clumping Factor A Mediates Binding Of Staphylococcus Aureus To Human Platelets, Ian R. Siboo, Ambrose L. Cheung, Arnold S. Bayer, Paul M. Sullam

Dartmouth Scholarship

The direct binding of bacteria to platelets may be an important virulence mechanism in the pathogenesis of infective endocarditis. We have previously described Staphylococcus aureus strain PS12, a Tn551-derived mutant of strain ISP479, with reduced ability to bind human platelets in vitro. When tested in an animal model of endocarditis, the PS12 strain was less virulent than its parental strain, as measured by bacterial densities in endocardial vegetations and incidence of systemic embolization. We have now characterized the gene disrupted in PS12 and its function in platelet binding. DNA sequencing, Southern blotting, and PCR analysis indicate that PS12 contained two …

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Integronlike Structures In Campylobacter Spp. Of Human And Animal Origin, Brigid Lucey, D. Crowley, P. Moloney, B. Cryan, M. Daly, F. O'Halloran, E. J. Threlfall, S. Fanning Feb 2000

Integronlike Structures In Campylobacter Spp. Of Human And Animal Origin, Brigid Lucey, D. Crowley, P. Moloney, B. Cryan, M. Daly, F. O'Halloran, E. J. Threlfall, S. Fanning

Department of Biological Sciences Publications

Resistance to antimicrobial agents used to treat severe Campylobacter spp. gastroenteritis is increasing worldwide. We assessed the antimicrobial resistance patterns of Campylobacter spp. isolates of human and animal origin. More than half (n = 32) were resistant to sulphonamide, a feature known to be associated with the presence of integrons. Analysis of these integrons will further our understanding of Campylobacter spp. epidemiology.

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Moraxella (Branhamella) Catarrhalis: A Molecular Epidemiology Study, Lyndell R. Gill May 1995

Moraxella (Branhamella) Catarrhalis: A Molecular Epidemiology Study, Lyndell R. Gill

Electronic Theses and Dissertations

Moraxella (Branhamella) catarrhalis is the third-most-frequently isolated microorganism associated with acute exacerbations of chronic bronchitis in patients during their stay at the Mountain Home VA Medical Center (MHVAMC). In order to develop a practical, epidemiologically-meaningful typing method for M. (B.) catarrhalis, we tested two methods based on analysis of chromosomal DNA for typeability, reproducibility, and ability to differentiate between unrelated strains (discriminatory power, D). M. (B.) catarrhalis isolants from MHVAMC from 7/1/87-6/30/88 were grown overnight in broth and embedded in agarose. DNA was isolated by standard methods. The DNA was subjected to: (1) restriction endonuclease digestion (with either Bgl II …

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Mycoplasmas In Plaque And Saliva Of Children And Their Relationship To Gingivitis, Holt R. D., Wilson M., Musa S. Jan 1995

Mycoplasmas In Plaque And Saliva Of Children And Their Relationship To Gingivitis, Holt R. D., Wilson M., Musa S.

Sabri Musa

GINGIVITIS IS COMMON IN CHILDREN but its etiology is not well understood. Results of earlier studies have suggested that mycoplasmas may have a role in the disease. In this study two plaque samples and one stimulated saliva sample were taken from each of a group of sixty (60) 5 to 9 year-old children and cultured selectively for mycoplasmas. Subjects had been selected on the basis of gingival status buccal to the most posterior tooth in an upper quadrant, 20 each having scores 0, 1, or 2 at this site using the Loe and Silness index. Plaque samples were taken from …

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Molecular And Cellular Analysis Of Chlamydia Trachomatis: Persistence And Reactivation, Kimberly R. Tau May 1992

Molecular And Cellular Analysis Of Chlamydia Trachomatis: Persistence And Reactivation, Kimberly R. Tau

Electronic Theses and Dissertations

Chlamydia trachomatis (CT) is the most prevalent sexually-transmitted infection in the United States. It has been suggested that CT infections can become latent. This has not been substantiated. CT persistence was examined at the molecular and cellular level in vitro and in vivo. Penicillin treatment of CT in vitro results in abnormal inclusions and reduced recovery of infectious CT. Penicillin did not inhibit initial stages of infection, but did downregulate CT rRNA levels after 25 hours post-inoculation (p.i.). DNA amplification was employed to differentiate between a resolved infection and a persistent one. Utilizing a primer pair that amplified a 144 …

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Microbiological Water Quality Of Impoundments: A Literature Review, G. Allen Burton Jr. Dec 1982

Microbiological Water Quality Of Impoundments: A Literature Review, G. Allen Burton Jr.

Public Health Resources

Assessing the microbiological water quality of impoundments and the potential for waterborne disease outbreaks is a difficult task when using traditional sampling programs. Problems associated with using fecal coliform bacteria as indicators of human pathogen presence complicates assessments of future water quality in preimpoundment areas. Reliable determination of future and present microbiological water quality requires knowledge of how the chemical, physical, and biological characteristics of the watershed and impoundment interrelate to influence microbial indicator and pathogen densities. Accurate estimates of microbial indicator and pathogen densities, obtainable by using the enumeration methods and their modifications suggested in this report, will allow …

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