Browsing by Author "Van Staden, Anton Du Preez"
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- ItemDeveloping bone cement implants impregnated with bacteriocins for prevention of infections(Stellenbosch : Stellenbosch University, 2011-12) Van Staden, Anton Du Preez; Dicks, Leon Milner Theodore; Stellenbosch University. Faculty of Science. Dept. of Microbiology.ENGLISH ABSTRACT: Infection is one of the major causes of increased morbidity and the escalating costs associated with orthopedic surgery. The areas that are infected are often difficult to reach and thus difficult to treat. In some surgeries antibiotic-loaded bone cements are used to control infection. Polymethylmethacrylate (PMMA) and calcium phosphate-based bone cements (CPC) are usually used as bone fillers. CPC are bioresorbable and biocompatible (unlike PMMA cements), but can only be used in non- or low-load bearing areas and are thus more applicable in cranio-and maxilla-facial surgeries. Several in vitro and in vivo trials have been conducted on the incorporation of antibiotics and other therapeutic agents into CPC and the release of these agents. As with any solid matrix, release is defined by specific parameters, i.e. matrix porosity, solubility of the drug and interaction of the drug with the cement. The increase in antibiotic-resistant pathogens, mainly as a result of overuse of antibiotics, has a major impact on the choice of antibiotics that are used in the treatment of bacterial infections. The search for alternative antimicrobial compounds that are active against resistant pathogens, is thus of utmost importance. Antimicrobial peptides (bacteriocins) produced by lactic acid bacteria may pose a possible alternative to antibiotics. Some of these peptides are active against antibiotic-resistant pathogens. Bacteriocins are small cationic, hydrophobic, or amphiphilic peptides active against a narrow range of target organisms. Most of these peptides are active in the nanomolar range. It may then be advantageous to incorporate bacteriocins into CPC to evaluate if they may be used as an alternative to antibiotics. The aim of the project was to evaluate if bacteriocins could be successfully incorporated into self seting brushite bone cement and remain effective in vivo without altering basic cement characteristics. Incorporation of bacteriocins into CPC is a novel concept. The low setting temperature and pH of CPC renders it the ideal matrix for incorporation of antimicrobial peptides. In this study, peptide ST4SA, a class IIa broad-spectrum bacteriocin, has been incorporated into brushite bone cement and characterized in vitro. Incorporation of the peptide did not have a significant effect on the crystal entanglement or setting reaction of the cement. Peptide ST4SA was rapidly released and inhibited the growth of the target strain effectively. In another experiment, peptide ST4SA was suspended in poly (lactide-co-glycolide) and electrosprayed to form micro particles that were entrapped in brushite cement. Association of the peptide with microparticles resulted in a delayed release from the cement, followed by a constant release. Nisin F, a class Ia bacteriocin was also incorporated into brushite cement and its activity studied in vitro and in vivo. Similar results were observed in vitro as recorded with peptide ST4SA incorporated into brushite cement. Small cylinders of brushite cement loaded with nisin F were implanted into subcutaneous pockets in mice and each pocket infected with a bioluminescent strain of Staphylococcus aureus (Xen 36). Nisin F in the bone cement prevented the growth of S. aureus in the wound and controlled infection. With this study we have shown that antimicrobial peptides that differ in structure (classes I and II) could be incorporated into bone cement and control the growth of S. aureus in vivo and in vitro. The mode of action of these peptides differs from antibiotics in that they form a permanent pore in the cell membrane of the target organism. This minimizes the chance of a strain becoming resistant to the peptide. Incorporation of antimicrobial peptides into bone cement may be a possible alternative to antibiotics in the control of bacterial infections associated with implants.
- ItemEfficacy of lantibiotic treatment of staphylococcus aureus-induced skin infections, monitored by in vivo bioluminescent imaging(American Society for Microbiology, 2016) Van Staden, Anton Du PreezStaphylococcus aureus is a bacterial pathogen responsible for the majority of skin and soft tissue infections. Antibiotics are losing their efficacy as treatment for skin and soft tissue infections as a result of increased resistance in a variety of pathogens, including S. aureus. It is thus imperative to explore alternative antimicrobial treatments to ensure future treatment options for skin and soft tissue infections. A select few lantibiotics, a group of natural defense peptides produced by bacteria, inhibit the growth of numerous clinical S. aureus isolates, including methicillin-resistant strains. In this study, the antimicrobial activities of nisin, clausin, and amyloliquecidin, separately administered, were compared to that of a mupirocin-based ointment, which is commonly used as treatment for S. aureus-induced skin infections. Full-thickness excisional wounds, generated on the dorsal surfaces of mice, were infected with a bioluminescent strain of S. aureus (strain Xen 36). The infections were monitored in real time using in vivo bioluminescent imaging. Lantibiotic treatments significantly reduced the bioluminescence of S. aureus Xen 36 to a level similar to that recorded with mupirocin treatment. Wound closure, however, was more pronounced during lantibiotic treatment. Lantibiotics thus have the potential to be used as an alternative treatment option for S. aureus-induced skin infections
- ItemIn vitro and In vivo characterization of Amyloliquecidin, a novel two-component lantibiotic produced by Bacillus amyloliquefaciens(Stellenbosch : Stellenbosch University, 2015-04) Van Staden, Anton Du Preez; Dicks, Leon Milner Theodore; Deane, Shelly May; Stellenbosch University. Faculty of Science. Dept. of Microbiology.ENGLISH ABSTRACT: Antimicrobial resistance is one of the major problems faced by the medical industry today. The ability of bacteria to rapidly acquire resistance against antibiotics and the over prescription and inappropriate use of antibiotics further exacerbate this crisis. Few new antimicrobials are, however, making it through the drug discovery pipeline. The search and development of novel and effective antimicrobials is therefore of the utmost importance. Lantibiotics are ribosomally synthesized cationic antimicrobial peptides with extensive post-translational modifications. They are active against a wide range of Gram-positive bacteria, including antibiotic-resistant strains. They are characterized by the presence of lanthionine and methyllanthionine rings and have been suggested as alternatives or for use in conjunction with antibiotics against resistant pathogens. Staphylococcus aureus is the most common bacteria isolated from skin and soft tissue infections (SSTIs). Strains of S. aureus have emerged with resistance against antibiotics with the most common being methicillin-resistant S. aureus (MRSA). Several lantibiotics are active against MRSA in vivo and have even shown superior activity to traditional antibiotics. Lantibiotics therefore show much promise for the treatment of SSTIs caused by resistant- and non-resistant S. aureus. In this study the bacterially diverse soil of the Fynbos in the Western Cape was screened for novel antimicrobials. Two antimicrobial producing Bacillus strains were isolated, Bacillus clausii AD1 and Bacillus amyloliquefaciens AD2. Both of these strains produce lantibiotics with B. clausii AD1 producing a known lantibiotic, clausin. B. amyloliquefaciens AD2 produces a novel two-component lantibiotic which was designated amyloliquecidin. The lantibiotic operon of amyloliquecidin was sequenced and annotated. All the genes required for successful production of amyloliquecidin are present in the operon. Amyloliquecidin was characterized in vitro and along with clausin is active against clinical strains of S. aureus (including MRSA), Enterococcus spp., Listeria spp. and beta-haemolytic streptococci. Amyloliquecidin has remarkable stability at physiological pH compared to nisin and clausin. A comparative in vivo murine infection model was used to evaluate the effectiveness of amyloliquecidin, nisin, clausin and Bactroban (commercial S. aureus topical treatment) in treating wound infections caused by S. aureus. All the lantibiotics proved to be just as effective as the Bactroban treatment. Furthermore, the tested lantibiotics did not have a negative influence on the wound closure rates of infected and non-infected wounds. Bactroban had a negative effect on wound healing compared to the lantibiotics. To our knowledge amyloliquecidin is the third two-component lantibiotic isolated from Bacillus. This study represents the first to test the effectiveness of amyloliquecidin in vivo and is one of a handful to test lantibiotics as topical treatments.