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Journal Article

Xen36, Xen 36, Staphylococcus aureus Xen36, IVIS

Aims: To determine if nisin F-loaded self-setting brushite cement could control the growth of Staphylococcus aureus in vivo. Methods and Results: Brushite cement was prepared by mixing equimolar concentrations of beta-tricalcium phosphate and monocalcium phosphate monohydrate. Nisin F was added at 5.0%, 2.5% and 1.0% (w/w) and the cement moulded into cylinders. In vitro antibacterial activity was determined using a delayed agar diffusion assay. Release of nisin F from the cement was determined using BCA protein assays. Based on scanning electron microscopy and X-ray diffraction analysis, nisin F did not cause significant changes in cement structure or chemistry. Cement containing 5.0% (w/w) nisin F yielded the most promising in vitro results. Nisin F-loaded cement was implanted into a subcutaneous pocket on the back of mice and then infected with S. aureus Xen 36. Infection was monitored for 7 days, using an in vivo imaging system. Nisin F prevented S. aureus infection for 7 days and no viable cells were isolated from the implants. Conclusions: Nisin F-loaded brushite cement successfully prevented in vivo growth of S. aureus. Significance and Impact of the Study: Nisin F incorporated into bone cement may be used to control S. aureus infection in vivo. (c) 2012The Authors Journal of Applied Microbiology (c) 2012 The Society for Applied Microbiology.

Journal Article

Xen31, Xen 31, MRSA, S. aureus, IVIS, Bioluminescence, Animals; Bacterial Infections/*drug therapy; Burns/drug therapy/microbiology; Candida/drug effects; Cations; Gram-Negative Bacteria/drug effects; Gram-Positive Bacteria/drug effects; Male; Methicillin-Resistant Staphylococcus aureus; Mice; Mice, Inbred BALB C; *Photochemotherapy; Photosensitizing Agents/*chemical synthesis/chemistry/pharmacology; Porphyrins/*chemical synthesis/chemistry/pharmacology; Solubility; Staphylococcal Infections/drug therapy/microbiology; Structure-Activity Relationship

Structures of typical photosensitizers used in antimicrobial photodynamic therapy are based on porphyrins, phthalocyanines, and phenothiazinium salts, with cationic charges at physiological pH values. However, derivatives of the porphycene macrocycle (a structural isomer of porphyrin) have barely been investigated as antimicrobial agents. Therefore, we report the synthesis of the first tricationic water-soluble porphycene and its basic photochemical properties. We successfully tested it for in vitro photoinactivation of different Gram-positive and Gram-negative bacteria, as well as a fungal species (Candida) in a drug-dose and light-dose dependent manner. We also used the cationic porphycene in vivo to treat an infection model comprising mouse third degree burns infected with a bioluminescent methicillin-resistant Staphylococcus aureus strain. There was a 2.6-log(10) reduction (p < 0.001) of the bacterial bioluminescence for the PDT-treated group after irradiation with 180 J.cm(-2) of red light.

Journal Article

Xen31, Xen 31, MRSA, S. aureus, IVIS, Bioluminescence, Animals; Arthritis, Infectious/*drug therapy/immunology/microbiology; *Immunity, Innate; Methicillin-Resistant Staphylococcus aureus/isolation & purification; Methylene Blue/therapeutic use; Mice; Neutrophils/*immunology; *Photochemotherapy; Photosensitizing Agents/therapeutic use

BACKGROUND: Local microbial infections induced by multiple-drug-resistant bacteria in the orthopedic field can be intractable, therefore development of new therapeutic modalities is needed. Photodynamic therapy (PDT) is a promising alternative modality to antibiotics for intractable microbial infections, and we recently reported that PDT has the potential to accumulate neutrophils into the infected site which leads to resolution of the infection. PDT for cancer has long been known to be able to stimulate the innate and adaptive arms of the immune system. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, a murine methicillin-resistant Staphylococcus aureus (MRSA) arthritis model using bioluminescent MRSA and polystyrene microparticles was established, and both the therapeutic (Th-PDT) and preventive (Pre-PDT) effects of PDT using methylene blue as photosensitizer were examined. Although Th-PDT could not demonstrate direct bacterial killing, neutrophils were accumulated into the infectious joint space after PDT and MRSA arthritis was reduced. With the preconditioning Pre-PDT regimen, neutrophils were quickly accumulated into the joint immediately after bacterial inoculation and bacterial growth was suppressed and the establishment of infection was inhibited. CONCLUSIONS/SIGNIFICANCE: This is the first demonstration of a protective innate immune response against a bacterial pathogen produced by PDT.

Journal Article

Xen31, Xen 31, MRSA, S. aureus, IVIS, Bioluminescence

Biofilms that develop on indwelling devices are a major concern in clinical settings. While removal of colonized devices remains the most frequent strategy for avoiding device-related complications, antibiotic lock therapy constitutes an adjunct therapy for catheter-related infection. However, currently used antibiotic lock solutions are not fully effective against biofilms, thus warranting a search for new antibiotic locks. Metal-binding chelators have emerged as potential adjuvants due to their dual anticoagulant/antibiofilm activities, but studies investigating their efficiency were mainly in vitro or else focused on their effects in prevention of infection. To assess the ability of such chelators to eradicate mature biofilms, we used an in vivo model of a totally implantable venous access port inserted in rats and colonized by either Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, or Pseudomonas aeruginosa. We demonstrate that use of tetrasodium EDTA (30 mg/ml) as a supplement to the gentamicin (5 mg/ml) antibiotic lock solution associated with systemic antibiotics completely eradicated Gram-positive and Gram-negative bacterial biofilms developed in totally implantable venous access ports. Gentamicin-EDTA lock was able to eliminate biofilms with a single instillation, thus reducing length of treatment. Moreover, we show that this combination was effective for immunosuppressed rats. Lastly, we demonstrate that a gentamicin-EDTA lock is able to eradicate the biofilm formed by a gentamicin-resistant strain of methicillin-resistant S. aureus. This in vivo study demonstrates the potential of EDTA as an efficient antibiotic adjuvant to eradicate catheter-associated biofilms of major bacterial pathogens and thus provides a promising new lock solution.

Journal Article

Xen29, Xen 29, Staphylococcus aureus Xen29, IVISBacterial Physiological Phenomena/drug effects; Bacterial Proteins/genetics/metabolism; Biofilms/*drug effects; *Down-Regulation/drug effects; Fungi/drug effects/physiology; Kingella kingae/chemistry/genetics/*metabolism; Molecular Sequence Data; Polysaccharides, Bacterial/biosynthesis/chemistry/*pharmacology

Cell-free extracts prepared from Kingella kingae colony biofilms were found to inhibit biofilm formation by Aggregatibacter actinomycetemcomitans, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Candida albicans, and K. kingae. The extracts evidently inhibited biofilm formation by modifying the physicochemical properties of the cell surface, the biofilm matrix, and the substrate. Chemical and biochemical analyses indicated that the biofilm inhibition activity in the K. kingae extract was due to polysaccharide. Structural analyses showed that the extract contained two major polysaccharides. One was a linear polysaccharide with the structure -->6)-alpha-d-GlcNAcp-(1-->5)-beta-d-OclAp-(2-->, which was identical to a capsular polysaccharide produced by Actinobacillus pleuropneumoniae serotype 5. The second was a novel linear polysaccharide, designated PAM galactan, with the structure -->3)-beta-d-Galf-(1-->6)-beta-d-Galf-(1-->. Purified PAM galactan exhibited broad-spectrum biofilm inhibition activity. A cluster of three K. kingae genes encoding UDP-galactopyranose mutase (ugm) and two putative galactofuranosyl transferases was sufficient for the synthesis of PAM galactan in Escherichia coli. PAM galactan is one of a growing number of bacterial polysaccharides that exhibit antibiofilm activity. The biological roles and potential technological applications of these molecules remain unknown.