Medical Microbiology Commons^™

The Bile Response Repressor Brer Regulates Expression Of The Vibrio Cholerae Breab Efflux System Operon, Francisca A. Cerda-Maira, Carol S. Ringelberg, Ronald K. Taylor

Dartmouth Scholarship

Enteric pathogens have developed several resistance mechanisms to survive the antimicrobial action of bile. We investigated the transcriptional profile of Vibrio cholerae O1 El Tor strain C6706 under virulence gene-inducing conditions in the presence and absence of bile. Microarray analysis revealed that the expression of 119 genes was affected by bile. The mRNA levels of genes encoding proteins involved in transport were increased in the presence of bile, whereas the mRNA levels of genes encoding proteins involved in pathogenesis and chemotaxis were decreased. This study identified genes encoding transcriptional regulators from the TetR family (vexR and breR) and …

Suppression Of Implanted Mda-Mb 231 Human Breast Cancer Growth In Nude Mice By Dietary Walnut, W. Elaine Hardman, Gabriela Ion

Biochemistry and Microbiology

Walnuts contain components that may slow cancer growth including omega 3 fatty acids, phytosterols, polyphenols, carotenoids, and melatonin. A pilot study was performed to determine whether consumption of walnuts could affect growth of MDA-MB 231 human breast cancers implanted into nude mice. Tumor cells were injected into nude mice that were consuming an AIN-76A diet slightly modified to contain 10% corn oil. After the tumors reached 3 to 5 mm diameter, the diet of one group of mice was changed to include ground walnuts, equivalent to 56 g (2 oz) per day in humans. The tumor growth rate from Day …

Accelerated High Fidelity Prion Amplification Within And Across Prion Species Barriers, Kristi M. Green, Joaquín Castilla, Tanya S. Seward, Dana L. Napier, Jean E. Jewell, Claudio Soto, Glenn C. Telling

Microbiology, Immunology, and Molecular Genetics Faculty Publications

Experimental obstacles have impeded our ability to study prion transmission within and, more particularly, between species. Here, we used cervid prion protein expressed in brain extracts of transgenic mice, referred to as Tg(CerPrP), as a substrate for in vitro generation of chronic wasting disease (CWD) prions by protein misfolding cyclic amplification (PMCA). Characterization of this infectivity in Tg(CerPrP) mice demonstrated that serial PMCA resulted in the high fidelity amplification of CWD prions with apparently unaltered properties. Using similar methods to amplify mouse RML prions and characterize the resulting novel cervid prions, we show that serial PMCA abrogated a transmission barrier …

Cd5 Plays An Inhibitory Role In The Suppressive Function Of Murine Cd4(+) Cd25(+) T(Reg) Cells., Trivikram Dasu, Joseph E Qualls, Halide Tuna, Chander Raman, Donald A Cohen, Subbarao Bondada

Microbiology, Immunology, and Molecular Genetics Faculty Publications

A subset of CD4(+) T cells, the CD4(+) CD25(+) regulatory T (T(reg)) cells in the lymphoid organs and peripheral blood are known to possess suppressive function. Previous in vitro and in vivo studies have indicated that T cell receptor (TCR) signal is required for development of such 'natural regulatory (T(reg)) cells' and for activation of the effector function of CD4(+) CD25(+) regulatory T cells. CD5 is a cell surface molecule present on all T cells and a subtype of B lymphocytes, the B-1 cells, primarily localized to coelomic cavities, Peyer's patches, tonsils and spleen. CD5 acts as a negative regulator …

Cd5 Plays An Inhibitory Role In The Suppressive Function Of Murine Cd4+ Cd25+ TReg Cells, Trivikram Dasu, Joseph E. Qualls, Halide Tuna, Chander Raman, Donald A. Cohen, Subbarao Bondada

Microbiology, Immunology, and Molecular Genetics Faculty Publications

A subset of CD4⁺ T cells, the CD4⁺ CD25⁺ regulatory T (T_reg) cells in the lymphoid organs and peripheral blood are known to possess suppressive function. Previous in vitro and in vivo studies have indicated that T cell receptor (TCR) signal is required for development of such ‘natural regulatory (T_reg) cells’ and for activation of the effector function of CD4⁺ CD25⁺ regulatory T cells. CD5 is a cell surface molecule present on all T cells and a subtype of B lymphocytes, the B-1 cells, primarily localized to coelomic cavities, Peyer's patches, …

The Effects Of Host Physiological Conditions On The Expression Of Icsp In Shigella Flexneri, Karen Levy, Helen Wing

Undergraduate Research Opportunities Program (UROP)

Shigella flexneri is a gram-negative bacterium capable of causing diarrhea and dysentery known as shigellosis. It is estimated there are 167.4 million shigellosis episodes throughout the world each year causing 1.1 million deaths. Shigella invades cells in the lower intestine through an induced phagocytosis. Once in the cytoplasm, bacteria move from one cell to another using actin-based motility. The Shigella outer membrane protease IcsP regulates actin-based motility and cell-to-cell spread by cleaving the actin assembly protein IcsA from the bacterial cell surface. We hypothesize that IcsP may serve additional functions during infection. By examining which environmental signals trigger icsP expression, …

Characterization Of The Omptin Protease, Ompt, In Escherichia Coli, Amanda Yates, Eun-Hae Kim, Helen Wing

Undergraduate Research Opportunities Program (UROP)

Omptins are outer membrane proteases found in gram negative bacteria that cause diseases in humans, such as pathogenic Escherichia coli, Shigella flexneri, Salmonella typhimurium, and Yersinia pestis. Bacterial species that express omptins cause diseases such as highly fatal plague and severe diarrhea and dysentery. The genes that encode these proteases are ompT, icsP, pgtE, and pla, respectively. These proteases are highly related in structure and share approximately 50% sequence identity. In S. flexneri, IcsP has been shown to cleave a key virulence determinant, IcsA (Egile et al., 1997). IcsA recruits host actin and allows for intracellular movement within host cells …

Relationship Of Lactobacillus Casei To Prevention Of Antibiotic Associated Diarrhea Due To Clostridium Difficile, Kayal K. Chandramohan

All-Inclusive List of Electronic Theses and Dissertations

The purpose of this research was to study the effectiveness of Lactobacillus casei in preventing the occurrence of antibiotic associated diarrhea related to Clostridium difficile. Twenty-six patients, above the age of sixty years, who were prescribed antibiotic therapy and admitted to the Rehabilitation or Orthopedics Units at Union Hospital and who met the eligibility criteria were recruited for the study. Equal numbers of patients (13 in each group) were assigned to the Control and the Experimental group based on their admission date to the hospital and their willingness to consume a probiotic yogurt type drink. The patients in the experimental …

Distinct Functions Of Autoreactive Memory And Effector Cd4+ T Cells In Experimental Autoimmune Encephalomyelitis, Wassim Elyaman, Pia Kivisäkk, Jay Reddy, Tanuja Chitnis, Khadir Raddassi, Jaime Imitola, Elizabeth Bradshaw, Vijay K. Kuchroo, Hideo Yagita, Mohamed H. Sayegh, Samia J. Khoury

Jay Reddy Publications

The persistence of human autoimmune diseases is thought to be mediated predominantly by memory T cells. We investigated the phenotype and migration of memory versus effector T cells in vivo in experimental autoimmune encephalomyelitis (EAE). We found that memory CD4⁺ T cells up-regulated the activation marker CD44 as well as CXCR3 and ICOS, proliferated more and produced more interferon-γ and less interleukin-17 compared to effector T cells. Moreover, adoptive transfer of memory T cells into T cell receptor (TCR)αβ^-/- recipients induced more severe disease than did effector CD4⁺ T cells with marked central nervous system inflammation and …

Neutralization Of Botulinum Neurotoxin By A Human Monoclonal Antibody Specific For The Catalytic Light Chain., Sharad P Adekar, Tsuyoshi Takahashi, R Mark Jones, Fetweh H Al-Saleem, Denise M Ancharski, Michael J Root, B P Kapadnis, Lance L Simpson, Scott K Dessain

Department of Biochemistry and Molecular Biology Faculty Papers

BACKGROUND: Botulinum neurotoxins (BoNT) are a family of category A select bioterror agents and the most potent biological toxins known. Cloned antibody therapeutics hold considerable promise as BoNT therapeutics, but the therapeutic utility of antibodies that bind the BoNT light chain domain (LC), a metalloprotease that functions in the cytosol of cholinergic neurons, has not been thoroughly explored.

METHODS AND FINDINGS: We used an optimized hybridoma method to clone a fully human antibody specific for the LC of serotype A BoNT (BoNT/A). The 4LCA antibody demonstrated potent in vivo neutralization when administered alone and collaborated with an antibody specific for …

Murine Monoclonal Anti-Idiotype Antibody 11d10 And Methods Of Use Thereof, Malaya Chatterjee, Kenneth A. Foon, Sunil K. Chatterjee

Microbiology, Immunology and Molecular Genetics Faculty Patents

The present invention provides a monoclonal anti-Idiotype antibody 11D10 that elicits an immune response against a specific epitope of a high molecular weight mucin of human milk fat globule (HMFG) and a hybridoma that produces 11D10. The hybridoma that produces 11D10 was selected by specific procedures. 11D10 induces an immunological response to HMFG in mice, rabbits, monkeys and patients with advanced HMFG-associated tumors. This invention provides compositions derived from polynucleotide sequences encoding the variable light and/or variable heavy regions of monoclonal anti-idiotype antibody 11D10, as well as polypeptides encoded thereby. The invention also provides compositions which can be used in …

Pcr-Based Assay Using Occult Blood Detection Cards For Detection Of Diarrheagenic Escherichia Coli In Specimens From Us Travelers To Mexico With Acute Diarrhea, Kevin A Grimes, Jamal A Mohamed, Herbert L Dupont, Ranjit S Padda, Zhi-Dong Jiang, Jose Flores, Jaime Belkind-Gerson, Francisco G Martinez-Sandoval, Pablo C Okhuysen

Faculty, Staff and Student Publications

Large field studies of travelers' diarrhea for multiple destinations are limited by the need to perform stool cultures on site in a timely manner. A method for the collection, transport, and storage of fecal specimens that does not require immediate processing and refrigeration and that is stable for months would be advantageous. This study was designed to determine if enterotoxigenic Escherichia coli (ETEC) and enteroaggregative E. coli (EAEC) DNA could be identified from cards that were processed for the evaluation of fecal occult blood. U.S. students traveling to Mexico during 2005 to 2007 were monitored for the occurrence of diarrheal …

Cif Is Negatively Regulated By The Tetr Family Repressor Cifr, Daniel P. Maceachran, Bruce A. Stanton, George A. O'Toole

Dartmouth Scholarship

We previously reported that the novel Pseudomonas aeruginosa toxin Cif is capable of decreasing apical membrane expression of the cystic fibrosis transmembrane conductance regulator (CFTR). We further demonstrated that Cif is capable of degrading the synthetic epoxide hydrolase (EH) substrate S-NEPC [(2S,3S)-trans-3-phenyl-2-oxiranylmethyl 4-nitrophenol carbonate], suggesting that Cif may be reducing apical membrane expression of CFTR via its EH activity. Here we report that Cif is capable of degrading the xenobiotic epoxide epibromohydrin (EBH) to its vicinal diol 3-bromo-1,2-propanediol. We also demonstrate that this epoxide is a potent inducer of cif gene expression. We show that the predicted TetR family transcriptional …

Genetic Evidence For An Alternative Citrate-Dependent Biofilm Formation Pathway In Staphylococcus Aureus That Is Dependent On Fibronectin Binding Proteins And The Grars Two-Component Regulatory System, Robert M. Q. Shanks, Michael A. Meehl, Kimberly M. Brothers, Raquel M. Martinez, Niles P. Donegan, Martha L. Graber, Ambrose L. Cheung, George A. O'Toole

Dartmouth Scholarship

We reported previously that low concentrations of sodium citrate strongly promote biofilm formation by Staphylococcus aureus laboratory strains and clinical isolates. Here, we show that citrate promotes biofilm formation via stimulating both cell-to-surface and cell-to-cell interactions. Citrate-stimulated biofilm formation is independent of the ica locus, and in fact, citrate represses polysaccharide adhesin production. We show that fibronectin binding proteins FnbA and FnbB and the global regulator SarA, which positively regulates fnbA and fnbB gene expression, are required for citrate's positive effects on biofilm formation, and citrate also stimulates fnbA and fnbB gene expression. Biofilm formation is also stimulated by several …

Clinical And Microbiological Aspects Of Linezolid Resistance Mediated By The Cfr Gene Encoding A 23s Rrna Methyltransferase, Cesar A Arias, Martha Vallejo, Jinnethe Reyes, Diana Panesso, Jaime Moreno, Elizabeth Castañeda, Maria V Villegas, Barbara E Murray, John P Quinn

Faculty, Staff and Student Publications

The cfr (chloramphenicol-florfenicol resistance) gene encodes a 23S rRNA methyltransferase that confers resistance to linezolid. Detection of linezolid resistance was evaluated in the first cfr-carrying human hospital isolate of linezolid and methicillin-resistant Staphylococcus aureus (designated MRSA CM-05) by dilution and diffusion methods (including Etest). The presence of cfr was investigated in isolates of staphylococci colonizing the patient's household contacts and clinical isolates recovered from patients in the same unit where MRSA CM-05 was isolated. Additionally, 68 chloramphenicol-resistant Colombian MRSA isolates recovered from hospitals between 2001 and 2004 were screened for the presence of the cfr gene. In addition to erm(B), …

Retinoic Acid Decreases Atf-2 Phosphorylation And Sensitizes Melanoma Cells To Taxol-Mediated Growth Inhibition, Ying Huang, Jennifer Minigh, Sarah Miles, Richard N. Niles

Biochemistry and Microbiology

Cutaneous melanoma is often resistant to chemo- and radiotherapy. This resistance has recently been demonstrated to be due, at least in part, to high activating transcription factor 2 (ATF-2) activity in these tumors. In concordance with these reports, we found that B16 mouse melanoma cells had higher levels of ATF-2 than immortalized, but non-malignant mouse melanocytes. In addition, the melanoma cells had a much higher amount of phosphorylated (active) ATF-2 than the immortalized melanocytes. In the course of determining how retinoic acid (RA) stimulates activating protein-1 (AP-1) activity in B16 melanoma, we discovered that this retinoid decreased the phosphorylation of …

N-Acetyl-B-D-Glucosaminidase And Inflammatory Response After Cardiopulmonary Bypass, Perwaiz Iqbal, Hasanat M Sharif, Naseema Mehboobali, Farzana A Yousuf, Abrar H Khan, Frank W Sellke

Department of Biological & Biomedical Sciences

OBJECTIVE: To determine the changes in activity of plasma N-acetyl-beta-D-glucosaminidase, a marker for inflammation as well as renal, pulmonary and cardiac damage and proinflammatory cytokines in patients undergoing coronary artery bypass grafting and find out the relationship between their plasma levels with clinical outcome of patients.

STUDY DESIGN: Cross-sectional study.

PLACE AND DURATION OF STUDY: The Aga Khan University, Karachi, from January to June 2003.

PATIENTS AND METHODS: N-acetyl-beta-D-glucosaminidase (NAG) activity and concentrations of tumor necrosis factor-alpha of (TNFalpha), interleukin 6 (IL-6), interleukin 8 (IL8) and granulocyte-macrophage colony stimulating factor (GM-CSF) were monitored in plasma samples of 12 angina patients …

In Vitro Analysis Of Tobramycin-Treated Pseudomonas Aeruginosa Biofilms On Cystic Fibrosis-Derived Airway Epithelial Cells, Gregory G. Anderson, Sophie Moreau-Marquis, Bruce A. Stanton, George A. O'Toole

Dartmouth Scholarship

P. aeruginosa forms biofilms in the lungs of individuals with cystic fibrosis (CF); however, there have been no effective model systems for studying biofilm formation in the CF lung. We have developed a tissue culture system for growth of P. aeruginosa biofilms on CF-derived human airway cells that promotes the formation of highly antibiotic-resistant microcolonies, which produce an extracellular polysaccharide matrix and require the known abiotic biofilm formation genes flgK and pilB. Treatment of P. aeruginosa biofilms with tobramycin reduced the virulence of the biofilms both by reducing bacterial numbers and by altering virulence gene expression. We performed microarray analysis …

Repression Of Hla By Rot Is Dependent On Sae In Staphylococcus Aureus, Dongmei Li, Ambrose Cheung

Dartmouth Scholarship

The regulatory locus sae is a two-component system in Staphylococcus aureus that regulates many important virulence factors, including alpha-toxin (encoded by hla) at the transcriptional level. The SarA homologs Rot and SarT were previously shown to be repressors of hla in selected S. aureus backgrounds. To delineate the interaction of rot and sae and the contribution of sarT to hla expression, an assortment of rot and sae isogenic single mutants, a rot sae double mutant, and a rot sae sarT markerless triple mutant were constructed from wild-type strain COL. Using Northern blot analysis and transcriptional reporter gene green fluorescent protein, …

Microglia And Astrocyte Activation By Toll-Like Receptor Ligands: Modulation By Ppar-Gamma Agonists., Catherine Gurley, Jessica Nichols, Shuliang Liu, Nirmal K. Phulwani, Nilufer Esen, Tammy Kielian

Journal Articles: Pathology and Microbiology

Microglia and astrocytes express numerous members of the Toll-like receptor (TLR) family that are pivotal for recognizing conserved microbial motifs expressed by a wide array of pathogens. Despite the critical role for TLRs in pathogen recognition, when dysregulated these pathways can also exacerbate CNS tissue destruction. Therefore, a critical balance must be achieved to elicit sufficient immunity to combat CNS infectious insults and downregulate these responses to avoid pathological tissue damage. We performed a comprehensive survey on the efficacy of various PPAR-gamma agonists to modulate proinflammatory mediator release from primary microglia and astrocytes in response to numerous TLR ligands relevant …

Conformational Changes And Flexibility In T-Cell Receptor Recognition Of Peptide–Mhc Complexes, Kathryn M. Armstrong, Kurt H. Piepenbrink, Brian M. Baker

Food for Health: Publications

A necessary feature of the immune system, TCR (T-cell receptor) cross-reactivity has been implicated in numerous autoimmune pathologies and is an underlying cause of transplant rejection. Early studies of the interactions of αβ TCRs (T-cell receptors) with their peptide–MHC ligands suggested that conformational plasticity in the TCR CDR (complementarity determining region) loops is a dominant contributor to T-cell cross-reactivity. Since these initial studies, the database of TCRs whose structures have been solved both bound and free is now large enough to permit general conclusions to be drawn about the extent of TCR plasticity and the types and locations of motion …

A Stable Explant Culture Of Her2/Neu Invasive Carcinoma Supported By Alpha-Smooth Muscle Actin Expressing Stromal Cells To Evaluate Therapeutic Agents, Marie P. Piechocki

Wayne State University Associated BioMed Central Scholarship

Abstract

Background

To gain a better understanding of the effects of therapeutic agents on the tumor microenvironment in invasive cancers, we developed a co-culture model from an invasive lobular carcinoma. Tumor cells expressing HER2/neu organize in nests surrounded by alpha-Smooth Muscle Actin (α-SMA) expressing tumor stroma to resemble the morphology of an invading tumor. This co-culture, Mammary Adenocarcinoma Model (MAM-1) maintains a 1:1 ratio of HER2/neu positive tumor cells to α-SMA-reactive stromal cells and renews this configuration for over 20 passages in vitro.

Methods

We characterized the cellular elements of the MAM-1 model by microarray analysis, and immunocytochemistry. We developed …

Autoimmune-Induced Preferential Depletion Of Myelin-Associated Glycoprotein (Mag) Is Genetically Regulated In Relapsing Eae (B6 × Sjl) F1 Mice, Dusanka S. Skundric, Rujuan Dai, Vaagn L. Zakarian, Weili Zhou

Wayne State University Associated BioMed Central Scholarship

Abstract

Background

Experimental autoimmune encephalomyelitis (EAE) is commonly used to investigate mechanisms of autoimmune-mediated damage to oligodendrocytes, myelin, and axons in multiple sclerosis (MS). Four distinct autoimmune mechanisms with subsequently distinct patterns of demyelination have been recognized in acute MS lesions. EAE correlates for those distinct patterns of MS lesions are unknown. An excessive loss of myelin-associated glycoprotein (MAG), as a result of distal oligodendrogliopathy, is found exclusively in the subtype III lesion. We sought to answer if types of demyelination in acute lesions during onset and relapse of EAE can replicate the specific patterns observed in MS acute lesions. …

A Novel Inhibitory Mechanism Of Mitochondrion-Dependent Apoptosis By A Herpesviral Protein, Pinghui Feng, Chengyu Liang, Young C. Shin, Xiaofei E, Weijun Zhang, Robyn Gravel, Ting-Ting Wu, Ren Sun, Edward Usherwood, Jae U. Jung

Dartmouth Scholarship

Upon viral infection, cells undergo apoptosis as a defense against viral replication. Viruses, in turn, have evolved elaborate mechanisms to subvert apoptotic processes. Here, we report that a novel viral mitochondrial anti-apoptotic protein (vMAP) of murine gamma-herpesvirus 68 (gammaHV-68) interacts with Bcl-2 and voltage-dependent anion channel 1 (VDAC1) in a genetically separable manner. The N-terminal region of vMAP interacted with Bcl-2, and this interaction markedly increased not only Bcl-2 recruitment to mitochondria but also its avidity for BH3-only pro-apoptotic proteins, thereby suppressing Bax mitochondrial translocation and activation. In addition, the central and C-terminal hydrophobic regions of vMAP interacted with VDAC1. …

Leptospira Interrogans Endostatin-Like Outer Membrane Proteins Bind Host Fibronectin, Laminin And Regulators Of Complement, Brian Stevenson, Henry A. Choy, Marija Pinne, Matthew L. Rotondi, M. Clarke Miller, Edward Demoll, Peter Kraiczy, Anne E. Cooley, Trevor P. Creamer, Marc A. Suchard, Catherine A. Brissette, Ashutosh Verma, David A. Haake

Microbiology, Immunology, and Molecular Genetics Faculty Publications

The pathogenic spirochete Leptospira interrogans disseminates throughout its hosts via the bloodstream, then invades and colonizes a variety of host tissues. Infectious leptospires are resistant to killing by their hosts' alternative pathway of complement-mediated killing, and interact with various host extracellular matrix (ECM) components. The LenA outer surface protein (formerly called LfhA and Lsa24) was previously shown to bind the host ECM component laminin and the complement regulators factor H and factor H-related protein-1. We now demonstrate that infectious L. interrogans contain five additional paralogs of lenA, which we designated lenB, lenC, lenD, lenE and lenF …

The Potential Role Of Probiotics In Reducing Poverty-Associated Infections In Developing Countries, Kingsley Anukam

Data and Test Instruments

Probiotics are defined by the Food and Agricultural Organization/ World Health Organization as “live microorganisms which when administered in adequate amounts confer a health benefit on the host” [1]. The potential benefits of their use have not been adequately investigated, especially in the developing world. Japan introduced Yakult, a probiotic fermented food drink in 1935, and in the Northern hemisphere, research and use of probiotics has gained an unprecedented momentum in the last decade [2]. Use of probiotics is not uncommon in Europe [3], but in many developing countries use of probiotics in its present definition is a foreign concept. …

Characterization Of Mazfsa, An Endoribonuclease From Staphylococcus Aureus, Zhibiao Fu, Niles P. Donegan, Guido Memmi, Ambrose L. Cheung

Dartmouth Scholarship

The mazEF homologs of Staphylococcus aureus, designated mazEF(sa), have been shown to cotranscribe with the sigB operon under stress conditions. In this study, we showed that MazEF(Sa), as with their Escherichia coli counterparts, compose a toxin-antitoxin module wherein MazF(Sa) leads to rapid cell growth arrest and loss in viable CFU upon overexpression. MazF(Sa) is a novel sequence-specific endoribonuclease which cleaves mRNA to inhibit protein synthesis. Using ctpA mRNA as the model substrate both in vitro and in vivo, we demonstrated that MazF(Sa) cleaves single-strand RNA preferentially at the 5' side of the first U or 3' side of the second …

All-Trans Retinoic Acid Mediates Enhanced T Reg Cell Growth, Differentiation, And Gut Homing In The Face Of High Levels Of Co-Stimulation, Micah J. Benson, Karina Pino-Lagos, Mario Rosemblatt, Randolph J. Noelle

Dartmouth Scholarship

We demonstrate that all-trans retinoic acid (RA) induces FoxP3(+) adaptive T regulatory cells (A-Tregs) to acquire a gut-homing phenotype (alpha 4 beta 7(+) CC chemokine receptor 9(+)) and the capacity to home to the lamina propria of the small intestine. Under conditions that favor the differentiation of A-Tregs (transforming growth factor-beta1 and interleukin 2) in vitro, the inclusion of RA induces nearly all activated CD4(+) T cells to express FoxP3 and greatly increases the accumulation of these cells. In the absence of RA, A-Treg differentiation is abruptly impaired by proficient antigen presenting cells or through direct co-stimulation. In the presence …

A Serratia Marcescens Oxyr Homolog Mediates Surface Attachment And Biofilm Formation, Robert M. Q. Shanks, Nicholas A. Stella, Eric J. Kalivoda, Megan R. Doe

Dartmouth Scholarship

OxyR is a conserved bacterial transcription factor with a regulatory role in oxidative stress response. From a genetic screen for genes that modulate biofilm formation in the opportunistic pathogen Serratia marcescens, mutations in an oxyR homolog and predicted fimbria structural genes were identified. S. marcescens oxyR mutants were severely impaired in biofilm formation, in contrast to the hyperbiofilm phenotype exhibited by oxyR mutants of Escherichia coli and Burkholderia pseudomallei. Further analysis revealed that OxyR plays a role in the primary attachment of cells to a surface. Similar to what is observed in other bacterial species, S. marcescens OxyR …

A Second Large Plasmid Encodes Conjugative Transfer And Antimicrobial Resistance In O119:H2 And Some Typical O111 Enteropathogenic Escherichia Coli Strains, Adaobi I. Nwaneshiudu, Tania Mucci, Derek J. Pickard, Iruka N. Okeke

Student Papers, Posters & Projects

A novel and functional conjugative transfer system identified in O119:H2 enteropathogenic Escherichia coli (EPEC) strain MB80 by subtractive hybridization is encoded on a large multidrug resistance plasmid, distinct from the well-described EPEC adherence factor (EAF) plasmid. Variants of the MB80 conjugative resistance plasmid were identified in other EPEC strains, including the prototypical O111:NM strain B171, from which the EAF plasmid has been sequenced. This separate large plasmid and the selective advantage that it confers in the antibiotic era have been overlooked because it comigrates with the virulence plasmid on conventional gels.