Citation Details

Journal Article

Acetamides; Animals; Anti-Bacterial Agents; Bioware; Colony Count, Microbial; Daptomycin; Female; Luminescent Measurements; Methicillin Resistance; Mice; Microbial Sensitivity Tests; Neutropenia; Oxazolidinones; Peritonitis; Staphylococcus aureus; Xen29

The rising rates of antibiotic resistance accentuate the critical need for new antibiotics. Daptomycin is a new antibiotic with a unique mode of action and a rapid in vitro bactericidal effect against gram-positive organisms. This study examined the kinetics of daptomycin's bactericidal action against peritonitis caused by methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in healthy and neutropenic mice and compared this activity with those of other commonly used antibiotics. CD-1 mice were inoculated intraperitoneally with lethal doses of MSSA (Xen-29) or MRSA (Xen-1), laboratory strains transformed with a plasmid containing the lux operon, which confers bioluminescence. One hour later, the animals were given a single dose of daptomycin at 50 mg/kg of body weight subcutaneously (s.c.), nafcillin at 100 mg/kg s.c., vancomycin at 100 mg/kg s.c., linezolid at 100 mg/kg via gavage (orally), or saline (10 ml/kg s.c.). The mice were anesthetized hourly, and photon emissions from living bioluminescent bacteria were imaged and quantified. The luminescence in saline-treated control mice either increased (neutropenic mice) or remained relatively unchanged (healthy mice). In contrast, by 2 to 3 h postdosing, daptomycin effected a 90% reduction of luminescence of MSSA or MRSA in both healthy and neutropenic mice. The activity of daptomycin against both MSSA and MRSA strains was superior to those of nafcillin, vancomycin, and linezolid. Against MSSA peritonitis, daptomycin showed greater and more rapid bactericidal activity than nafcillin or linezolid. Against MRSA peritonitis, daptomycin showed greater and more rapid bactericidal activity than vancomycin or linezolid. The rapid decrease in the luminescent signal in the daptomycin-treated neutropenic mice underscores the potency of this antibiotic against S. aureus in the immune-suppressed host.

Journal Article

Amino Acid Sequence; Animals; Antimicrobial Cationic Peptides; Bacterial Infections; Bioware; Cell Line; Cells, Cultured; Chemokine CCL2; Chemokine CCL7; Chemokine CXCL1; Chemokines; Female; Humans; Interleukin-8; Leukocytes; Leukocytes, Mononuclear; Macrophages; Mice; Mice, Inbred C57BL; Molecular Sequence Data; NF-kappa B; p38 Mitogen-Activated Protein Kinases; Phosphatidylinositol 3-Kinases; Phosphorylation; Staphylococcal Infections; Staphylococcus aureus; Xen29, Xen14

With the rapid rise in the incidence of multidrug resistant infections, there is substantial interest in host defense peptides as templates for production of new antimicrobial therapeutics. Natural peptides are multifunctional mediators of the innate immune response, with some direct antimicrobial activity and diverse immunomodulatory properties. We have previously developed an innate defense regulator (IDR) 1, with protective activity against bacterial infection mediated entirely through its effects on the immunity of the host, as a novel approach to anti-infective therapy. In this study, an immunomodulatory peptide IDR-1002 was selected from a library of bactenecin derivatives based on its substantially more potent ability to induce chemokines in human PBMCs. The enhanced chemokine induction activity of the peptide in vitro correlated with stronger protective activity in vivo in the Staphylococcus aureus-invasive infection model, with a >5-fold reduction in the protective dose in direct comparison with IDR-1. IDR-1002 also afforded protection against the Gram-negative bacterial pathogen Escherichia coli. Chemokine induction by IDR-1002 was found to be mediated through a Gi-coupled receptor and the PI3K, NF-kappaB, and MAPK signaling pathways. The protective activity of the peptide was associated with in vivo augmentation of chemokine production and recruitment of neutrophils and monocytes to the site of infection. These results highlight the importance of the chemokine induction activity of host defense peptides and demonstrate that the optimization of the ex vivo chemokine-induction properties of peptides is a promising method for the rational development of immunomodulatory IDR peptides with enhanced anti-infective activity.

Journal Article

Bacterial Adhesion; Biocompatible Materials; Biofilms; Bioware; Coated Materials, Biocompatible; Materials Testing; Polyethylene Glycols; Staphylococcus aureus; Staphylococcus epidermidis; Surface Properties; Xen29

Poly(ethylene glycol) (PEG) coatings are known to reduce microbial adhesion in terms of numbers and binding strength. However, bacterial adhesion remains of the order of 10(4)cm(-2). It is unknown whether this density of bacteria will eventually grow into a biofilm. This study investigates the kinetics of staphylococcal biofilm formation on a commercially produced, robust, cross-linked PEG-based polymer coating (OptiChem) in vitro and in vivo. OptiChem inhibits biofilm formation in vitro, and although adsorption of plasma proteins encourages biofilm formation, microbial growth kinetics are still strongly delayed compared to uncoated glass. In vivo, OptiChem-coated and bare silicone rubber samples were inserted into an infected murine subcutaneous pocket model. In contrast to bare silicone rubber, OptiChem samples did not become colonized upon reimplantation despite the fact that surrounding tissues were always culture-positive. We conclude that the commercial OptiChem coating considerably slows down bacterial biofilm formation both in vitro and in vivo, making it an attractive candidate for biomaterials implant coating.

Journal Article

Animals; Anti-Bacterial Agents; Biofilms; Bioware; Drug Resistance, Bacterial; Mice; Mutation; Rifampin; Staphylococcus aureus; Xen29

OBJECTIVES To investigate in vivo fitness of rifampicin-resistant Staphylococcus aureus mutants in a mouse biofilm model using bioluminescence imaging. MATERIALS AND METHODS S. aureus was engineered with a luciferase operon to emit bioluminescence that can be detected in vivo using an IVIS imaging system. Two rifampicin-resistant strains of S. aureus that were previously isolated from animals undergoing rifampicin treatment, S464P (resistant to low concentrations of rifampicin) and H481Y (resistant to high concentrations of rifampicin), were characterized and then compared with their parental strain for in vivo fitness to form biofilm infections in the absence of rifampicin. RESULTS The mutant S464P showed better adaptation to in vivo growth than either the parental strain or H481Y without selective pressure. Six days after implanting pre-colonized catheters, bioluminescent signals were seen from 100% of the catheters coated by the mutant S464P. In comparison, only 83% and 61% of the catheters coated by the parental strain and H481Y, respectively, maintained a signal in vivo. Rifampicin treatment of S464P biofilms in vivo resulted in a slight decline, but earlier rebound in bioluminescence from these catheters compared with the parental signal, whereas rifampicin had no affect on bioluminescence in mice infected with mutant H481Y. CONCLUSIONS The mutant with low-level rifampicin resistance appears to be better adapted to in vivo growth than the mutant that has high-level rifampicin resistance. Moreover, the former mutant may actually have a slight competitive advantage over the rifampicin-susceptible strain (parental), raising awareness for the occurrence of such strains in clinical environments.

Journal Article

Anti-Bacterial Agents; Biofilms; Bioware; Bone Substitutes; Bone Transplantation; Prostheses and Implants; Prosthesis-Related Infections; Staphylococcal Infections; Staphylococcus aureus; Transplantation, Homologous; Vancomycin; Xen36

BACKGROUND Bone grafts are frequently used to supplement bone stock and to establish structural stability. However, graft-associated infection represents a challenging complication leading to increased patient morbidity and healthcare costs. QUESTIONS/PURPOSES We therefore designed this study to (1) determine if increasing initial S. aureus inoculation of bone allograft results in a proportionate increase in colonization; (2) assess if antibiotics decrease colonization and if antibiotic tethering to allograft alters its ability to prevent bacterial colonization; and (3) determine if covalent modification alters the allograft topography or its biological properties. METHODS Allograft bone and vancomycin-modified bone (VAN-bone) was challenged with different doses of S. aureus for times out to 24 hours in the presence or absence of solution vancomycin. Bacterial colonization was assessed by fluorescence, scanning electron microscopy (SEM), and by direct colony counting. Cell density and distribution of osteoblast-like cells on control and modified allograft were then compared. RESULTS Bacterial attachment was apparent within 6 hours with colonization and biofilm formation increasing with time and dose. Solution vancomycin failed to prevent bacterial attachment whereas VAN-bone successfully resisted colonization. The allograft modification did not affect the attachment and distribution of osteoblast-like cells. CONCLUSIONS Allograft bone was readily colonized by S. aureus and covered by a biofilm with especially florid growth in natural topographic niches. Using a novel covalent modification, allograft bone was able to resist colonization by organisms while retaining the ability to allow adhesion of osteoblastic cells. CLINICAL RELEVANCE Generation of allograft bone that can resist infection in vivo would be important in addressing one of the most challenging problems associated with the use of allograft, namely infection.