Doctoral Degrees (Microbiology)

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Browsing Doctoral Degrees (Microbiology) by Subject "Antibiotics"

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    Development of an antimicrobial wound dressing by co-electrospinning bacteriocins of lactic acid bacteria into polymeric nanofibers
    (Stellenbosch : Stellenbosch University, 2012-12) Heunis, Tiaan de Jager; Dicks, Leon Milner Theodore; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: Skin is the largest organ in the human body and serves as a barrier that protects the underlying tissue of the host from infection. Injury, however, destroys this protective barrier and provides a perfect opportunity for microorganisms to invade the host and cause infection, thereby affecting the normal wound healing processes. Furthermore, the ability of microbial pathogens to rapidly develop resistance towards a variety of antimicrobial compounds hampers the effective treatment and control of infections. Antimicrobial-resistant pathogens are increasingly being isolated from patients, placing a huge burden on the health care sector. The search for new and novel antimicrobial agents and treatments is thus of utmost importance and will continue to play an integral role in medical research. Antimicrobial peptides (AMPs) may serve as possible alternatives to antibiotics, or may be used in combination with antibiotics to reduce the risk of antimicrobial resistance. AMPs play a role in innate defence and are produced by a variety of mammals, plants, reptiles, amphibians, birds, fish and insects. The AMPs of bacteria (bacteriocins), especially those of lactic acid bacteria (LAB), are receiving increased attention as antimicrobial agents to treat bacterial infections. Electrospun nanofibers have characteristics that make them suitable as wound dressings, i.e. high oxygen permeability, variable pore size, high surface area to volume ratio and nanofibers are morphologically similar to the extracellular matrix. The ability to incorporate of a variety of biologically active compounds into nanofibers increases their potential as wound dressings. A novel approach would be to incorporate bacteriocins from LAB into nanofiber scaffolds to generate antimicrobial wound dressings. In this study, the feasibility of co-electrospinning bacteriocins from LAB into nanofibers was investigated. Plantaricin 423, produced by Lactobacillus plantarum 423, was successfully co-electrospun into poly(ethylene oxide) (PEO) nanofibers. Plantaricin 423 retained activity after the electrospinning process and continued to inhibit the growth of Lactobacillus sakei DSM 20017T and Enterococcus faecium HKLHS. Viable cells of L. plantarum 423 were also successfully co-electrospun into PEO nanofibers, albeit with a slight reduction in viability. A nanofiber drug delivery system was developed for plantaricin 423 and bacteriocin ST4SA, produced by Enterococcus mundtii ST4SA, by blending PEO and poly(D,L-lactide) (PDLLA) in a suitable solvent before electrospinning. Nanofibers were produced that released the bacteriocins over an extended time period. The PEO:PDLLA (50:50) nanofiber scaffold retained its structure the best upon incubation at 37 °C and released active plantaricin 423 and bacteriocin ST4SA. Nisin A was also successfully co-electrospun into a PEO:PDLLA (50:50) nanofiber scaffold and nisin A, released from the nanofibers, inhibited the growth of Staphylococcus aureus in vitro. Nisin A-containing nanofiber scaffolds significantly reduced viable S. aureus cells in infected skin wounds and promoted wound healing in non-infected wounds. As far as we could determine we are the first to show that bacteriocin-eluting nanofiber scaffolds can be used to treat skin infections and influence wound healing.