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  • 1
    Language: English
    In: Gene, 2011, Vol.477(1), pp.19-23
    Description: is a Gram-negative aerobic diplococcus that is a mucosal pathogen of the upper and lower respiratory tracts in humans. In order to colonize the human host and establish an infection, must be able to effectively attach to the respiratory mucosal epithelia. Although little is known about pathogenesis, our laboratory has previously shown that expression of type IV pili (TFP) contributes to mucosal colonization. TFP are filamentous surface appendages primarily composed of a single protein subunit termed pilin, which is encoded by in . These surface structures play a crucial role in the initiation of disease by a wide range of pathogenic bacteria. Our studies also indicate that unlike the pilin of the pathogenic species, which exhibit both phase and antigenic variation, the pilin subunit of appears to be more highly conserved as there are no major pilin variants produced by a single strain and only two major PilA antigenic variants, termed clade 1 and clade 2, have been observed between strains. Moreover, we have determined that these highly conserved bacterial surface structures are expressed by all clinical isolates evaluated. Therapeutic or vaccine-based interventions that prevent or diminish nasopharyngeal colonization will likely decrease acute and recurrent infections in prone populations. Thus, our data indicate that additional studies aimed at elucidating the role of PilA in the pathogenesis and host response to infections are warranted.
    Keywords: Pili ; Pilin ; Antigenic Clades ; Engineering ; Biology ; Anatomy & Physiology
    ISSN: 0378-1119
    E-ISSN: 1879-0038
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  • 2
    Language: English
    In: Biomaterials, February 2015, Vol.41, pp.97-105
    Description: Effective treatment options are often limited for implant-associated orthopedic infections. In this study we evaluated the antimicrobial effects of applying cathodic voltage-controlled electrical stimulation (CVCES) of -1.8 V (vs. Ag/AgCl) to commercially pure titanium (cpTi) substrates with preformed biofilm-like structures of methicillin-resistant Staphylococcus aureus (MRSA). The in vitro studies showed that as compared to the open circuit potential (OCP) conditions, CVCES of -1.8 V for 1 h significantly reduced the colony-forming units (CFU) of MRSA enumerated from the cpTi by 97% (1.89 × 106 vs 6.45 × 104 CFU/ml) and from the surrounding solution by 92% (6.63 × 105 vs. 5.15 × 104 CFU/ml). The in vivo studies, utilizing a rodent periprosthetic infection model, showed that as compared to the OCP conditions, CVCES at -1.8 V for 1 h significantly reduced MRSA CFUs in the bone tissue by 87% (1.15 × 105 vs. 1.48 × 104 CFU/ml) and reduced CFU on the cpTi implant by 98% (5.48 × 104 vs 1.16 × 103 CFU/ml). The stimulation was not associated with histological changes in the host tissue surrounding the implant. As compared to the OCP conditions, the −1.8 V stimulation significantly increased the interfacial capacitance (18.93 vs. 98.25 μF/cm ) and decreased polarization resistance (868,250 vs. 108 Ω-cm ) of the cpTi. The antimicrobial effects are thought to be associated with these voltage-dependent electrochemical surface properties of the cpTi.
    Keywords: Titanium ; Infection ; Electrical Stimulation ; Antimicrobial ; Bacteria ; Biofilm ; Medicine ; Engineering
    ISSN: 0142-9612
    E-ISSN: 1878-5905
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  • 3
    Language: English
    In: Lasers in surgery and medicine, November 2014, Vol.46(9), pp.712-7
    Description: Moraxella catarrhalis is a significant cause of pediatric otitis media (OM), which is the most prevalent bacterial infection in children and primary reason for antibiotic administration in this population. Moreover, biofilm formation has been implicated as a primary mechanism of chronic or recurrent OM disease. As bacterial biofilms are inherently resistant to most antibiotics and these complex structures also present a significant challenge to the immune system, there is a clear need to identify novel antimicrobial approaches to treat OM infections. In this study, we evaluated the potential efficacy of antibacterial photodynamic therapy (aPDT) with porfimer sodium (Photofrin (PF)) against planktonic as well as biofilm-associated M. catarrhalis. The bactericidal activity of aPDT with PF was assessed against multiple recent clinical isolates of M. catarrhalis grown planktonically as well as in biofilms. The bactericidal activity of PF-aPDT was quantified by enumeration of colony forming units post-treatment. The effect of aPDT on M. catarrhalis biofilms was further investigated with scanning electron microscopy (SEM) imaging. aPDT with PF significantly reduced M. catarrhalis viability. Although PF-aPDT caused higher killing in planktonic grown organisms (5-6 log kill), biofilm grown bacteria also demonstrated a statistically significant reduction in viable organisms (3-4 log decrease in recoverable bacteria) following treatment as compared to saline only controls (P 〈 0.01). SEM studies indicated the PF-aPDT treated bacteria exhibited prominent morphological changes with visibly distorted cell membranes. aPDT with PF elicits significant bactericidal activity against both planktonic and biofilm-associated M. catarrhalis, suggesting this technology warrants further analysis as a potential novel antimicrobial treatment for acute or recurrent OM.
    Keywords: Antimicrobial Photodynamic Therapy ; Biofilm ; Gram-Negative Bacteria ; Otitis Media ; Photofrin ; Photochemotherapy ; Biofilms -- Drug Effects ; Dihematoporphyrin Ether -- Pharmacology ; Moraxella (Branhamella) Catarrhalis -- Drug Effects ; Photosensitizing Agents -- Pharmacology
    ISSN: 01968092
    E-ISSN: 1096-9101
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  • 4
    Language: English
    In: Journal of biomedical materials research. Part B, Applied biomaterials, January 2018, Vol.106(1), pp.221-227
    Description: Magnesium alloys hold great promise for developing orthopedic implants that are biocompatible, biodegradable, and mechanically similar to bone tissue. This study evaluated the in vitro and in vivo antimicrobial properties of magnesium-9%aluminum-1%zinc (AZ91) and commercially pure titanium (cpTi) against Acinetobacter baumannii (Ab307). The in vitro results showed that as compared to cpTi, incubation with AZ91 significantly reduced both the planktonic (cpTi = 3.45e8, AZ91 = 8.97e7, p 〈 0.001) colony forming units (CFU) and biofilm-associated (cpTi = 3.89e8, AZ91 = 1.78e7, p = 0.01) CFU of Ab307. However, in vivo results showed no significant differences in the CFU enumerated from the cpTi and AZ91 implants following a 1-week implantation in an established rodent model of Ab307 implant associated infection (cpTi = 5.23e3, AZ91 = 2.46e3, p = 0.29). It is proposed that the in vitro results were associated with an increased pH in the bacterial culture as a result of the AZ91 corrosion process. The robust in vivo buffering capacity likely diminished this corrosion associated pH antimicrobial effect. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 221-227, 2018.
    Keywords: Antimicrobial ; Biodegradable ; in Vivo ; Infection ; Magnesium ; Acinetobacter Baumannii -- Growth & Development ; Alloys -- Pharmacology ; Anti-Infective Agents -- Pharmacology ; Implants, Experimental -- Microbiology ; Magnesium -- Pharmacology
    ISSN: 15524973
    E-ISSN: 1552-4981
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  • 5
    Language: English
    In: Environmental Modelling and Software, April 2018, Vol.102, pp.274-291
    Description: The modelling community has identified challenges for the integration and assessment of lake models due to the diversity of modelling approaches and lakes. In this study, we develop and assess a one-dimensional lake model and apply it to 32 lakes from a global observatory network. The data set included lakes over broad ranges in latitude, climatic zones, size, residence time, mixing regime and trophic level. Model performance was evaluated using several error assessment metrics, and a sensitivity analysis was conducted for nine parameters that governed the surface heat exchange and mixing efficiency. There was low correlation between input data uncertainty and model performance and predictions of temperature were less sensitive to model parameters than prediction of thermocline depth and Schmidt stability. The study provides guidance to where the general model approach and associated assumptions work, and cases where adjustments to model parameterisations and/or structure are required.
    Keywords: Lake Model ; Stratification ; Glm ; Model Assessment ; Global Observatory Data ; Network Science ; Engineering ; Environmental Sciences ; Computer Science ; Ecology
    ISSN: 1364-8152
    E-ISSN: 1873-6726
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  • 6
    Language: English
    In: Proceedings of SPIE, 16 August 2000, Vol.4008(1), pp.797-805
    Description: EMIR is a near-IR, multi-slit camera-spectrograph under development for the 10m GTC on La Palma. It will deliver up to 45 independent R equals 3500-4000 spectra of sources over a field of view of 6 feet by 3 feet, and allow NIR imaging over a 6 foot by 6 foot FOV, with spatial sampling of 0.175 inch/pixel. The prime science goal of the instrument is to open K-band, wide field multi-object spectroscopy on 10m class telescopes. Science applications range from the study of star-forming galaxies beyond z equals 2, to observations of substellar objects and dust-enshrouded star formation regions. Main technological challenges include the large optics, the mechanical and thermal stability and the need to implement a mask exchange mechanism that does not require warming up the spectrograph. EMIR is begin developed by the Instituto de Astrofisica de Canarias, the Instituto Nacional de Tecnica Aeroespacial, the Universidad Complutense de Madrid, the Observatoire Midi-Pyrennees, and the University of Durham. Currently in its Preliminary Design phase, EMIR is expected to start science operation in 2004.
    Keywords: Engineering
    ISBN: 9780819436337
    ISSN: 0277-786X
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