In silico Predicted Glucose-1-phosphate Uridylyltransferase (GalU) Inhibitors Block a Key Pathway Required for Listeria Virulence.

Peptidoglycan walls of gram positive bacteria are functionalized by glycopolymers called wall teichoic acid (WTA). In Listeria monocytogenes, multiple enzymes including the glucose-1-phosphate uridylyltransferase (GalU) were identified as mandatory for WTA galactosylation, so that the inhibition of GalU is associated with a significant attenuation of Listeria virulence. Herein, we report on a series of in silico predicted GalU inhibitors identified using structure-based virtual screening and experimentally validated to be effective in blocking the WTA galactosylation pathway in vitro.

Antibacterial efficacy and cytotoxicity of low intensity direct current activated silver-titanium implant system prototype.

Silver-based devices activated by electric current are of interest in biomedicine because of their broad-spectrum antimicrobial activity. This study investigates the in vitro antibacterial efficacy and cytotoxicity of a low intensity direct current (LIDC)-activated silver-titanium implant system prototype designed for localized generation and delivery of silver ions at the implantation site. First, the antibacterial efficacy of the system was assessed against methicillin-resistant Staphylococcus aureus (MRSA) over 48 h at current levels of 3 and 6 µA in Mueller-Hinton broth.

Use of bacteriophage to target bacterial surface structures required for virulence: a systematic search for antibiotic alternatives.

Bacteriophages (phage) that infect pathogenic bacteria often attach to surface receptors that are coincidentally required for virulence. Receptor loss or modification through mutation renders mutants both attenuated and phage resistant. Such attenuated mutants frequently have no apparent laboratory growth defects, but in the host, they fail to exhibit properties needed to produce disease such as mucosal colonization or survival within professional phagocytic cells.

Listeria monocytogenes wall teichoic acid decoration in virulence and cell-to-cell spread.

Wall teichoic acid (WTA) comprises a class of glycopolymers covalently attached to the peptidoglycan of gram positive bacteria. In Listeria monocytogenes, mutations that prevent addition of certain WTA decorating sugars are attenuating. However, the steps required for decoration and the pathogenic process interrupted are not well described.

Evaluation of silver-titanium implants activated by low intensity direct current for orthopedic infection control: An in vitro and in vivo study.

Silver is an alternative antimicrobial of interest for the prophylaxis of prosthetic infections and electrical activation is known to augment its oligodynamic efficacy. In this study, we evaluated the in vitro and in vivo efficacy of a silver (Ag)-titanium (Ti) implant activated by 30 µA direct current compared with three controls - passive Ag-Ti, active Ti-Ti, and passive Ti-Ti. We hypothesized that the experimental group would provide better resistance to pathogenic colonization on the implant.

Effects of cathode design parameters on in vitro antimicrobial efficacy of electrically-activated silver-based iontophoretic system.

Post-operative infection is a major risk associated with implantable devices. Prior studies have demonstrated the effectiveness of ionic silver as an alternative to antibiotic-based infection prophylaxis and treatment. The focus of this study is on an electrically activated implant system engineered for active release of antimicrobial silver ions.

The Haemophilus ducreyi trimeric autotransporter adhesin DsrA protects against an experimental infection in the swine model of chancroid.

Adherence of pathogens to cellular targets is required to initiate most infections. Defining strategies that interfere with adhesion is therefore important for the development of preventative measures against infectious diseases. As an adhesin to host extracellular matrix proteins and human keratinocytes, the trimeric autotransporter adhesin DsrA, a proven virulence factor of the Gram-negative bacterium Haemophilus ducreyi, is a potential target for vaccine development.

Extrauterine listeriosis in the gravid mouse influences embryonic growth and development.

Gravid mice and other rodents inoculated with Listeria monocytogenes typically fail to clear an intrauterine infection and either succumb or expel their intrauterine contents. We took advantage of this property to investigate the effects of an extrauterine infection on parameters of pregnancy success. Pregnant mice were selected for our study if they showed no clinical signs of listeriosis following oral inoculation at 7.

Biocompatibility analysis of an electrically-activated silver-based antibacterial surface system for medical device applications.

The costs associated with the treatment of medical device and surgical site infections are a major cause of concern in the global healthcare system. To prevent transmission of such infections, a prophylactic surface system that provides protracted release of antibacterial silver ions using low intensity direct electric current (LIDC; 28 μA system current at 6 V) activation has been recently developed. To ensure the safety for future in vivo studies and potential clinical applications, this study assessed the biocompatibility of the LIDC-activated interdigitated silver electrodes-based surface system; in vitro toxicity to human epidermal keratinocytes, human dermal fibroblasts, and normal human osteoblasts, and antibacterial efficacy against Staphylococcus aureus and Escherichia coli was evaluated.

In vitro properties of a Listeria monocytogenes bacteriophage-resistant mutant predict its efficacy as a live oral vaccine strain.

A Listeria monocytogenes glcV mutation precludes the binding of certain listerial phages and produces a profound attenuation characterized by the absence of detectable mutants in the livers and spleens of orally inoculated mice. In vitro, we found that the mutant formed plaques on mouse enterocyte monolayers as efficiently as the parent but the plaques formed were smaller. Intracellular growth rate determinations and examination of infected enterocytes by light and fluorescence microscopy established that the mutant was impaired not in intracellular growth rate but in cell-to-cell spreading.

Passive immunization with a polyclonal antiserum to the hemoglobin receptor of Haemophilus ducreyi confers protection against a homologous challenge in the experimental swine model of chancroid.

Haemophilus ducreyi, the etiologic agent of chancroid, has an obligate requirement for heme. Heme is acquired by H. ducreyi from its human host via TonB-dependent transporters expressed at its bacterial surface.

Incorporation of secretory immunoglobulin A into biofilms can decrease their resistance to ciprofloxacin.

Extracellular matrices utilized by biofilms growing on inert surfaces are generally produced entirely by the bacteria growing within those biofilms, whereas symbiotic (mutualistic) biofilms growing in or on a wide range of plants and animals utilize host-derived macromolecules, such as mucoid substances, as components of their extracellular matrix. Incorporation of host-derived molecules may have a profound effect on the resistance to antibiotics of symbiotic biofilms, which may have important implications for medicine and biology. As an initial probe of the potential effects of host-derived molecules in the extracellular matrix on the sensitivity of biofilms to antibiotics, an in vitro model was used to evaluate the effects of ciprofloxacin on biofilms grown in the presence and absence of SIgA, a host-derived glycoprotein associated with biofilms in the mammalian gut.

Antibacterial efficacy of silver nanoparticles of different sizes, surface conditions and synthesis methods.

Silver nanoparticles (Ag-nps) are used as a natural biocide to prevent undesired bacterial growth in clothing and cosmetics. The objective of this study was to assess the antibacterial efficacy of Ag-nps of different sizes, surface conditions, and synthesis methods against Escherichia coli, Ag-resistant E. coli, Staphylococcus aureus, methicillin-resistant S.

Factors associated with the acquisition and severity of gestational listeriosis.

Gravid mammals are more prone to listeriosis than their nongravid counterparts. However, many features of the disease in gravid animals are not well defined. We determined, in mice, that increased susceptibility to lethal infection following oral inoculation begins surprisingly early in pregnancy and extends through embryonic development.

Immunization with the Haemophilus ducreyi hemoglobin receptor HgbA with adjuvant monophosphoryl lipid A protects swine from a homologous but not a heterologous challenge.

Haemophilus ducreyi, the etiological agent of chancroid, has a strict requirement for heme, which it acquires from its only natural host, humans. Previously, we showed that a vaccine preparation containing the native hemoglobin receptor HgbA purified from H. ducreyi class I strain 35000HP (nHgbAI) and administered with Freund's adjuvant provided complete protection against a homologous challenge.

Adaptation in a mouse colony monoassociated with Escherichia coli K-12 for more than 1,000 days.

Although mice associated with a single bacterial species have been used to provide a simple model for analysis of host-bacteria relationships, bacteria have been shown to display adaptability when grown in a variety of novel environments. In this study, changes associated with the host-bacterium relationship in mice monoassociated with Escherichia coli K-12 over a period of 1,031 days were evaluated. After 80 days, phenotypic diversification of E.

Identification and characterization of two Bordetella avium gene products required for hemagglutination.

Bordetella avium causes bordetellosis in birds, a disease similar to whooping cough caused by Bordetella pertussis in children. B. avium agglutinates guinea pig erythrocytes via an unknown mechanism.

Quantitative glycomics from fluidic glycan microarrays.

A hallmark of cell-surface processes involving glycans is their multivalent interaction with glycan binding proteins (GBPs). Such a multivalent interaction depends critically on the mobility and density of signaling molecules on the membrane surface. While glycan microarrays have been used in exploring multivalent interactions, the lack of mobility and the difficulty in controlling surface density both limit their quantitative applications.

Altering and assessing persistence of genetically modified E. coli MG1655 in the large bowel.

One of the primary factors limiting the efficacy of probiotic therapies is short persistence time. Utilizing a novel method for assessment of persistence in the large bowel independent of survival of the organisms in the upper GI tract, we tested whether overexpression of the type 1 pilus, a colonization factor, or the presence of secretory immunoglobulin A (sIgA) might increase the persistence time of a laboratory strain of E. coli in the gut.

A Listeria monocytogenes mutant defective in bacteriophage attachment is attenuated in orally inoculated mice and impaired in enterocyte intracellular growth.

A Listeria monocytogenes bacteriophage was used to identify a phage-resistant Tn917 insertion mutant of the mouse-virulent listerial strain F6214-1. The mutant was attenuated when it was inoculated orally into female A/J mice and failed to replicate efficiently in cultured mouse enterocytes. Phage binding studies indicated that the mutant had a cell surface alteration that precluded phage attachment.

Comparison of the genome sequence of the poultry pathogen Bordetella avium with those of B. bronchiseptica, B. pertussis, and B. parapertussis reveals extensive diversity in surface structures associated with host interaction.

Bordetella avium is a pathogen of poultry and is phylogenetically distinct from Bordetella bronchiseptica, Bordetella pertussis, and Bordetella parapertussis, which are other species in the Bordetella genus that infect mammals. In order to understand the evolutionary relatedness of Bordetella species and further the understanding of pathogenesis, we obtained the complete genome sequence of B. avium strain 197N, a pathogenic strain that has been extensively studied.

Expression of Haemophilus ducreyi collagen binding outer membrane protein NcaA is required for virulence in swine and human challenge models of chancroid.

Haemophilus ducreyi, the etiologic agent of the sexually transmitted genital ulcer disease chancroid, has been shown to associate with dermal collagen fibers within infected skin lesions. Here we describe NcaA, a previously uncharacterized outer membrane protein that is important for H. ducreyi collagen binding and host colonization.

Immunization with the Haemophilus ducreyi hemoglobin receptor HgbA protects against infection in the swine model of chancroid.

The etiologic agent of chancroid is Haemophilus ducreyi. To fulfill its obligate requirement for heme, H. ducreyi uses two TonB-dependent receptors: the hemoglobin receptor (HgbA) and a receptor for free heme (TdhA).

Host and bacterial factors in listeriosis pathogenesis.

Members of the Genus Listeria are ubiquitous environmental saprophytic microorganisms. If ingested they can cause a severe disseminated disease (listeriosis) that has a high mortality rate, the highest of any food-borne pathogen, even with antibiotic therapy. Central to the high mortality rate is the hallmark characteristic of the microorganism to grow intracellularly.

Secretory IgA and mucin-mediated biofilm formation by environmental strains of Escherichia coli: role of type 1 pili.

Recent studies suggest the importance of secretory IgA (SIgA) and mucin in the mediation of biofilm formation by commensal bacteria within the mammalian gut. Studies using a variety of strains of Escherichia coli have indicated that the interaction between E. coli and SIgA is dependent on the type 1 pilus.