Periodontal infection can manifest itself in many different clinical presentations. The aggressive form of this disease is frequently seen in the younger patient population referred for treatment to the Temple University Kornberg School of Dentistry (TUKSD). This study was done to assess the demographics of aggressive periodontitis cases and the types of periodontal treatment methods provided to these patients, antibiotic prescription patterns and compliance with treatment. A chart review was conducted to identify cases of aggressive periodontitis in patients <30 years of age referred for treatment at the Graduate Periodontology and Oral Implantology Clinic, TUKSD. The diagnosis of aggressive periodontitis was validated by presence of characteristic radiographic bone loss at permanent incisors and molars. Exclusion criteria were deficient radiographs, and a medical history of systemic diseases that compromise the immune response. Twenty-two aggressive periodontitis cases were identified among 300 charts surveyed. All patients were 12-26 years old. The patient sample was comprised mainly of African American race-ethnicity, with no predominance of a sex group. Initial treatment with scaling and root planing, was done in 64% of cases with 36% dropout before treatment. Microbial plaque testing was done in 46% of cases, and 59% received systemic antibiotics. A combination antibiotic therapy regimen was often used in combination with nonsurgical periodontal therapy. Most patients did not present for treatment beyond the non-surgical phase, and some even before the treatment started. Because periodontal non-surgical treatment of aggressive periodontitis cases in the pre-doctoral clinic takes relatively long time, it is recommended that the treatment of these cases be expedited by referring the patients to the graduate clinic for all periodontal treatment including the initial phase. / Biology

Coatings play a pivotal role in everyday life and across various industries. They offer protection, corrosion resistance, insulation, optical improvements, aesthetics, etc. This study investigates the design, fabrication, characterization and evaluation of surface coatings in two areas: antimicrobial activity and fast evaporation. The COVID-19 pandemic underscored the necessity for coatings that mitigate microbial transmission through surfaces, alleviating both contagion and personal fears. The first part of this study presents the design, development, and evaluation of antimicrobial coatings that efficiently inactivate 99.9% of SARS-CoV-2 virus and kill more than 99.9% of pathogenic bacteria such as Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa within one hour. Prioritizing rapid infectivity reduction, we designed and fabricated several coatings using silver oxide (Ag2O), cupric oxide (CuO), and zinc oxide (ZnO) particles as active ingredients. Applying small quantities of micron-sized opaque particles onto a surface yields a transparent film. Although Ag2O particles are inherently opaque, they possess potent antimicrobial properties. Consequently, incorporating small quantities of Ag2O into the coating results in the desired antimicrobial activity while maintaining transparency. Transparent antimicrobial coatings are a necessity for applications such as touchscreens, offering the benefit of reducing disease transmission while maintaining the aesthetic appeal of surfaces. We employed a variant of the Stöber process to bind Ag2O particles to the substrate using a silica matrix. To improve this coating method, we employed room-temperature spin-coating of a suspension of Ag2O/sodium silicate solution on the substrate, eliminating reactions with toxic chemicals in Stöber process and subsequent heat treatment. Two key features of the improved coating are its high robustness and its capability to kill 98.6% of Clostridioides difficile endospores in 60 minutes. On the other hand, CuO and ZnO particles exhibit mild antimicrobial properties; thus, their activity could be enhanced by a porous coating. When an infected droplet lands on such a coating, it is imbibed into the porous structure, where diffusion distances are smaller, and there is a larger active area to inactivate the virus or kill the bacteria. Furthermore, porosity facilitates faster droplet drying, leading to the concentration of cupric and zinc ions in the droplet, which are designed to be toxic to microbes. The second major topic of this thesis is the development, and evaluation of porous coatings for fast evaporation. At low Bond numbers, droplet evaporation is slow on an impermeable surface. We investigated whether application of a thin, porous coating leads to faster droplet evaporation. The droplet will imbibe quickly, but progress normal to the interface will be limited to the thickness of the coating. Therefore, the liquid will spread laterally into a broad disk to expose a large liquid–vapor interface for evaporation. As a result, the evaporation of a droplet is enhanced by a factor of 7–8 on the thin porous coatings. Factors such as coating thickness, pore size and distribution, and the contact angle of the coating, as well as ambient conditions like temperature and relative humidity, could affect the droplet evaporation rates by modifying the droplet's imbibition process and the evaporation driving force. While decreasing the coating thickness and increasing pore size and distribution promoted evaporation, the impact of contact angle is insignificant. Confocal microscopy observations of a coating composed of particles with varying sizes depicted liquid migration along the top of the coating and the edges of the interface. We developed and validated an equation to estimate the rate of evaporation. The rate correlated with the radius of the imbibition area, with higher temperatures and lower humidity further augmenting evaporation. / Doctor of Philosophy / Coatings serve as integral components in various industries and everyday settings, offering multifaceted benefits such as protection, aesthetic enhancement, and functional properties. This study investigates the design, fabrication, and evaluation of two types of surface coatings; coatings that reduce microbes transmission (antimicrobial coatings) and coatings that expedite evaporation. The COVID-19 pandemic underscored the necessity for coatings that mitigate microbial transmission through surfaces, alleviating both contagion and personal fears. The first part of this study presents the design, development, and evaluation of coatings that efficiently reduce 99.9% of COVID-19 virus and kill more than 99.9% of dangerous bacteria that can be found in hospital settings. Prioritizing rapid killing of bacteria, we designed and fabricated several coatings using metal oxides. In particular, we used silver oxide (Ag2O), cupric oxide (CuO), and zinc oxide (ZnO) particles as active ingredients. Applying small quantities of fine-sized opaque particles onto a surface yields a transparent film. Although Ag2O particles are inherently opaque, they possess potent antimicrobial properties. Consequently, incorporating small quantities of Ag2O into the coating results in the desired antimicrobial activity while maintaining transparency. Transparent antimicrobial coatings are a necessity for applications such as touchscreens, offering the benefit of reducing disease transmission while maintaining the aesthetic appeal of surfaces. A chemical reaction was used to produce a glass matrix to bind Ag2O particles to the solid, but this method required heating and toxic chemicals. So we developed a second methods that eliminated these two disadvantages. On the other hand, CuO and ZnO particles exhibit milder antimicrobial properties; thus, their activity could be enhanced by a porous coating. These coatings function as large reservoirs of antimicrobial agents for trapping and deactivating pathogens, while facilitating rapid droplet evaporation through enhanced wicking and porous structure. The second part of this study elucidates the mechanisms underlying accelerated droplet drying as a result of the application of thin, porous coatings. The speed of drying is slow for small droplets on flat surfaces. However, when a droplet is placed on a porous coating, it will be wicked quickly and spread through the porous coating to create a large area for evaporation. As a result, the speed of drying was increased by a factor of 7–8 on the thin porous coatings. Coating parameters such as thickness, pore size, and distribution, surface energy, as well as environmental factors like temperature and humidity could influence the droplet drying from porous surfaces. Decreasing the coating thickness and increasing pore size and variation in pore size promoted droplet evaporation, whereas the impact of surface energy was found to be insignificant. The rate of drying correlated with the radius of the wetted area, with higher temperatures and lower humidity further augmenting evaporation.

It is predicted that by 2050 there will be 10 million deaths annually due to super-resistant bacterial infections. Antimicrobial resistance (AMR) is already responsible for nearly 5 million deaths a year. Ribosomes serve as an ideal drug target being frequently targeted by antibiotics and having a highly conserved structure with few options for resistance. However, computer aided drug design (CADD) using ribosome crystal structures presents several challenges and is underutilized in the field. In this work we establish a successful protocol for antibiotic redocking and docking within the high interest sites of the peptidyl transferase center (PTC). Molecular visualization and interaction mapping were used to atomistically delineate binding patterns in the ribosomal PTC that could be used for CADD. Eleven ribosome crystal structures were validated for computational testing, which revealed derivative binding patterns in the A-site and P-site that can be used to increase antibiotic efficacy. Ribosome overlays revealed high interaction frequency nucleotides that were widely conserved throughout the different species and could be used to inform bidentate design to target two pockets at once. This work serves as a basis for methods to computationally explore drug optimization on ribosome targeting antibiotics to help combat the rapid expansion of AMR. / Master of Science in Life Sciences / Antimicrobial resistance (AMR) to antibiotics by bacteria is a rapidly increasing problem. Current trends predict that there will be more death due to super-resistant bacterial strains than cancer by 2050. Ribosomes are essential cellular machinery for bacteria and make an ideal antibiotic target. Using computational tools to optimize antibiotics with available ribosome crystal structural data presents several challenges and is underutilized throughout the field. In this work we establish a successful protocol for determining and exploiting antibiotic binding patterns within the functional center of the ribosome, the peptidyl transfer center (PTC). Nearly a dozen ribosome crystal structures were validated for computational testing, and binding patterns were revealed within the PTC that allowed antibiotic derivatives with increased efficacy to be developed. Ribosome validation also helped inform new drug class design so that multiple drug sites could be targeted at once, which were docked sharing high frequency nucleotide interactions with both parent antibiotics. This work serves as a basis for methods to computationally explore drug optimization on ribosome targeting antibiotics to help combat the rapid expansion of AMR.

Pathogenic E. coli infections cause approximately one quarter of disease losses in commercial turkey flocks. A small subgroup of E. coli causes most infections. Epidemiologic studies of this disease have been hindered by a lack of reliable markers to discriminate between pathogenic and fecal E. coli and by the diversity of poultry strains. Reliance on antimicrobials to control E. coli infections has caused widespread antimicrobial resistance. One hundred five clinical E. coli were obtained, and 1104 isolates were collected from fecal specimens of 20 flocks in an integrated turkey operation. Biochemical fingerprinting and antimicrobial susceptibility tests were performed on all isolates, and somatic antigen serologic testing and PCR for potential virulence genes were conducted on 299 strains including all clinical isolates and fecal isolates that had similar traits to clinical isolates. Most avian E. coli infections were caused by a few clonal strains that were uncommon in normal fecal flora. The potential virulence genes iss, K1 and tsh were detected more frequently among clinical than fecal isolates; however, the pattern of occurrence did not suggest that these genes were useful markers for identifying pathogenic strains. Syndromes consistent with colibacillosis were the most commonly reported illness and principal rationale for antimicrobial therapy in sampled flocks. Most clinical E. coli isolates were resistant to gentamicin, sulfamethoxazole and tetracycline. Although resistance to fluoroquinolones and β-lactam antibiotics occurred less frequently, the potential for resistance to emerge to these antimicrobials was evident. A Bayesian model to estimate sample size confirmed the diversity of avian fecal E. coli strains. Studies are needed to define risk factors for infection with and identify markers for avian pathogenic E. coli strains. These research priorities are complementary and may lead to the identification of new interventions to prevent this important infectious disease of poultry. / Ph. D.

Yes / Microbial keratitis can arise from penetrating injuries to the cornea. Corneal trauma promotes bacterial attachment and biofilm growth, which decrease the effectiveness of antimicrobials against microbial keratitis. Improved therapeutic efficacy can be achieved by reducing microbial burden prior to antimicrobial therapy. This paper assesses a highly-branched poly(N-isopropyl acrylamide) with vancomycin end groups (HB-PNIPAM-van), for reducing bacterial attachment and biofilm formation. The polymer lacked antimicrobial activity against Staphylococcus aureus, but significantly inhibited biofilm formation (p = 0.0008) on plastic. Furthermore, pre-incubation of S. aureus cells with HB-PNIPAM-van reduced cell attachment by 50% and application of HB-PNIPAM-van to infected ex vivo rabbit corneas caused a 1-log reduction in bacterial recovery, compared to controls (p = 0.002). In conclusion, HB-PNIPAM-van may be a useful adjunct to antimicrobial therapy in the treatment of corneal infections. / Medical Research Council and the Department of Biotechnology, India under grant number, MR/N50188/2.

The increasing use of non-sustainable materials in technology has led to severe environmental consequences, prompting a global search for more sustainable and eco-friendly alternatives. Clay, with its low cost, non-toxicity, recyclability, natural abundance, and versatile properties, has emerged as a beacon of hope for a greener future. Since prehistoric times, clay has found extensive use in the pharmaceutical, petroleum, biomedical, and energy industries. Its high surface area, cation exchange capacity, intrinsic porosity, and ease of functionalization make it a versatile and sustainable choice for a variety of applications. The dissertation focuses on synthesizing hybrid clays functionalized with zwitterionic molecules for antimicrobial and ionic membrane applications. It also studies the rheological properties of bentonite clay modified with betaines of different carbon chain lengths. The research aims to investigate the flow and stability of these functionalized clays. In addition, it offers valuable insights into how carbon chain length and pH affect the rheological properties of clays. This is followed by engineering pathogen-resistant clay composites embedded with antimicrobial agents like silver ions and terbinafine hydrochloride against pathogens (viz. S. aureus, E. coli, and C. albicans). Another part of the dissertation focuses on developing and investigating flexible and durable betaine-functionalized clay membranes as ion-conducting separators for batteries and fuel cells. The low-cost membranes exhibit excellent ionic conductivity, chemical-thermal stability, recyclability, and ease of engineering making them an exceptional material for such applications. Overall, this dissertation presents a comprehensive study of the structure-property relationship of hybrid clays, bridging the fields of chemistry, materials engineering, electrochemistry, and biology. The research is poised to inspire the scientific and industrial communities with the potential of novel clay-based materials, encouraging them to embrace cleaner technologies and reduce their carbon footprints.

Osteomyelitis or infection of bone is painful and difficult to treat due to limited tissue penetration by antibiotics. A resulting chronic infection has around a 30% chance of never resolving and resulting in amputation of the limb. The current standard of care for osteomyelitis is debridement and systemic antibiotics for two to six months, which can cause systemic toxicity and increase the emergence of antibiotic-resistant bacteria. It is therefore necessary to develop a localized biodegradable treatment that can deliver high concentrations of antimicrobials while minimizing the risk of systemic side effects. The overall objective of this work was to develop, characterize, and challenge locally delivered chitosan-based biomaterials loaded with either antibiotic or alternative antimicrobial agent(s) in either chronic or acute rat osteomyelitis models. The specific aims were to: (i) determine the chemical and biological interactions between chitosan hydrogels and fosfomycin in vitro, (ii) evaluate the antimicrobial efficacy of chitosan hydrogel loaded with fosfomycin antibiotic, either in the gel, in polylactic acid microparticles, or in both gel and microparticles in vitro and in a chronic rat osteomyelitis model, compared to blank chitosan hydrogel, and (iii) evaluate the antimicrobial efficacy of electrospun chitosan membranes loaded with cis-2-decenoic acid and/or bupivacaine in an acute rat osteomyelitis model, compared to current standard Celox™gauze. As hypothesized, chitosan biomaterials loaded with antimicrobial(s) reduced the bacterial burden and disease symptoms when compared to the standard treatment or blank materials. In closing, locally administrated antibiotics with prolonged availability via engineered biomaterials such as chitosan may allow for increased therapeutic efficacy against osteomyelitis.

Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / Michael D. Apley / The discovery of modern antimicrobials in the early 20th century revolutionized treatment of infectious diseases. Less than 100 years later, antimicrobial resistance has become a global threat to public health. With the rise of antimicrobial resistance, the question that remains to be answered is: Can dosing regimens provide maximal clinical efficacy, yet minimize the development of antimicrobial resistance? A pharmacokinetic / pharmacodynamic approach was utilized to investigate oxytetracycline regimens that would impart efficacy while minimizing the potential for resistance development due to plasmid transfer. An in vitro pharmacodynamic model was used to quantify the response of a Pasteurella multocida isolate to two oxytetracycline dosing regimens. The PK/PD index most closely related to efficacy was the Cmax:MIC. The in vitro pharmacodynamic model was then used to investigate the effects of antimicrobial exposure on plasmid transfer. A mixed population of oxytetracycline-susceptible and resistant bacteria was exposed to two dosing regimens and plasmid transfer was quantified. When oxytetracycline concentrations exceeded the MIC of the recipient, development of resistance was suppressed. The same donor and recipient bacteria were used in an in situ swine model to validate the in vitro findings. Following surgical implantation of porous membrane straws containing the mixed bacterial population, animal subjects in the treatment groups received one of two oxytetracycline treatments. Oxytetracycline concentrations in the plasma and interstitial fluid were quantified. Plasmid transfer within the implant membranes was quantified and correlated to pharmacokinetic measures in the animal. Plasmid transfer rates in the implant membranes did not correlate to the investigated pharmacokinetic parameters. The study methodologies in this dissertation should serve as a foundation for future studies in antimicrobial pharmacokinetic/pharmacodynamic research. The results presented here show that the bacterial response to oxytetracycline can be optimized in a concentration dependent manner and that antimicrobial resistance development through plasmid transfer can be suppressed in vitro when oxytetracycline concentrations exceed the MIC of the recipient bacteria. These results suggest that a proper balance between clinical efficacy and minimizing antimicrobial resistance can be achieved for oxytetracycline through appropriate dosing regimens and drug formulations.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Biofouling is the attachment and biofilm formation that leads to negative repercussions such as persistent post-harvest infections, infections obtained from medical implants and continual surface contamination of food processing plants. Much of the problem lies with the resistance that develops against conventional treatments due to the formation of mature biofilms. Thus the focus has shifted from the removal of biofilms to the prevention of initial attachment of organisms. This entails the use of antimicrobial surfaces that either have an inherent antimicrobial activity, e.g. certain metals, or surfaces that are modified by the attachment of antimicrobial agents. The attachment of antimicrobial agents can either be through covalent bonding or adsorption, depending on the intended use of the surface as well as the mode of action of the antimicrobial agent. Antimicrobial peptides (AMPs) are ubiquitous in nature, tend to have a broad spectrum of activity, are very stable and have been shown to maintain activity when covalently bound to solid surfaces. Tyrocidines (Trcs), antimicrobial peptides produced by Bacillus aneurinolyticus, are cyclodecapeptides with a broad spectrum of activity against Grampositive bacteria, fungi, yeasts and the human malaria parasite, Plasmodium falciparum. The aim of this study was to determine the antimicrobial activity of surfaces treated with a tyrocidine extract, under which conditions the activity remained stable and to look into possible applications of these peptide-treated surfaces. The study focussed on different solid surfaces namely mixed cellulose, polyvinylidene fluoride, polycarbonate, cellulose acetate, cellulose (paper)(CL) and high density cellulose packing material (HDC), as a pilot study to assess the antimicrobial activity of Trc and gramicidin S (GS) treated solid surfaces. Peptide desorption and subsequent analysis by mass spectrometry was used to confirm the presence and integrity of the Trcs adsorbed. Scanning electron microscopy was utilised to show that the adsorbed peptides did not affect the structural integrity of the treated filters. However, it was shown that the adsorbed peptides changed the hydrophobic/hydrophilic character by means of a wettability assay. A cell viability assay and erythrocyte assay were developed from existing methodologies to determine the biological activity of the AMP-functionalised polymeric material. Seven of the AMP treated solid surfaces showed antimicrobial activity when challenged with >105 Micrococcus luteus cells/cm2. Although the polycarbonate filter lost antimicrobial activity at the high cell concentrations, it was shown to have potent antimicrobial activity at lower cell concentrations. Complete inhibition of M. luteus growth was observed for both the gramicidin S and tyrocidine extract treated high density cellulose and cellulose filters. Stability tests showed that the tyrocidines remained adsorbed to cellulose filters and biologically active when exposed multiple water washes, water washes at different temperatures (25°C - 100°C) and pH changes (pH 1-12). The antimicrobial activity was only affected after exposure to the water wash of pH 13 which is possible due to susceptibility of the CL filters to high pH solvents. A preliminary study on the effect of Trcs treated CL filters on the sterilization, germination and effect on tomato seedlings was conducted. It was found that Trcs had no effect on the germination and did not fully sterilise the seeds or environment against fungi. However, it was observed that 5 μg/mL Trcs treated filters promoted root length opposed to the toxic effect seen with filters treated with higher Trc concentrations. It is hypothesised that Trcs prefer to bind to hydrophilic surfaces exposing the hydrophobic residues and the cationic residue of the peptide to interact with the bacterial membrane to elicit its antimicrobial response. The exposed residues contain some of the hydrophobic residues and the cationic Orn9/Lys9, which are crucial to the antimicrobial activity of the peptides. Hydrophobic interaction is particularly important for the haemolytic activity which is currently the only viable method of detection of the adsorbed Trcs. Trcs also have a preference for adsorption onto cellulose and cellulose analogues which points to possible application in protective food wrapping and wood surface protection. Trcs maintains its antimicrobial activity regardless of adsorption to solid surfaces. It can therefore be concluded that Trcs treated solid surfaces hold great potential in preventing the initial bacterial colonization and subsequent biofilm formation. Antimicrobial peptide enriched solid surfaces can thus be developed and tailored to a specific application such as filters, catheters and packaging materials. / AFRIKAANSE OPSOMMING: Biovervuiling is die aanhegting en vorming van biofilms met negatiewe gevolge soos aanhoudende na-oes infeksies, infeksies op mediese inplantings en voortdurende oppervlak besoedeling van voedselverwerkings fabrieke. Die probleem lê grotendeels by die weerstand wat ontwikkel word teen konvensionele behandelings as gevolg van die vorming van volwasse biofilms. Die fokus het gevolglik verskuif vanaf die verwydering van biofilms na die voorkoming van aanvanklike aanhegting van organismes aan oppervlaktes. Dit behels die gebruik van antimikrobiese oppervlaktes wat of 'n inherente antimikrobiese aktiwiteit het, bv. sekere metale óf oppervlaktes wat aangepas is deur die aanhegting van antimikrobiese middels. Die aanhegting van antimikrobiese agente kan of deur kovalente binding óf adsorpsie plaasvind, afhangende van die beoogde gebruik van die oppervlak, sowel as die metode van werking van die antimikrobiese agent. Antimikrobiese peptiede (AMPe) is alomteenwoordig in die natuur, is geneig om 'n breë spektrum van aktiwiteit te hê, is baie stabiel en het getoon dat aktiwiteit in stand gehou word wanneer dit kovalent gebind word op soliede oppervlaktes. Tirosidiene (Trcs), antimikrobiese peptiede wat deur Bacillus aneurinolyticus geproduseer word, is siklodekapeptiede met 'n breë spektrum van aktiwiteit teen Gram-positiewe bakterieë, swamme, giste en die menslike malaria parasiet Plasmodium falciparum. Die doel van hierdie studie was om die antimikrobiese aktiwiteit te bepaal van oppervlaktes wat met 'n tirosidien ekstrak behandel is, te bepaal onder watter omstandighede die aktiwiteit stabiel bly en om te soek na moontlike toepassings van hierdie peptied-behandelde oppervlaktes. Die studie het gefokus op verskillende soliede oppervlaktes naamlik gemengde sellulose, polyvinylidene fluoried, polikarbonaat, sellulose asetaat, sellulose (papier)(CL) en 'n hoë digtheid sellulose verpakkings materiaal (HDC), as 'n loodsstudie om die antimikrobiese aktiwiteit van die Trcs en gramisidien S (GS) behandelde soliede oppervlaktes te ondersoek. Peptied-desorpsie en daaropvolgende ontleding deur massaspektroskopie is gebruik om die teenwoordigheid en integriteit van die geadsorbeerde Trcs te bevestig. Skandering elektronmikroskopie is gebruik om aan te toon dat die geadsorbeerde peptiede geen invloed op die strukturele integriteit van die behandelde filters het nie. Daar is egter getoon dat die geadsorbeerde peptiede die hidrofobiese / hidrofiliese karakter verander. „n Lewensvatbaarheid selgebaseerde toets en eritrosiet toets is ontwikkel uit bestaande metodes om die biologiese aktiwiteit van die AMP-gefunktionaliseerde polimeriese materiaal te bepaal. Sewe van die AMP behandel soliede oppervlaktes het antimikrobiese aktiwiteit getoon wanneer dit met > 105 Micrococcus luteus selle/cm2 gedaag is. Hoewel die polikarbonaat filter antimikrobiese aktiwiteit met hoë sel konsentrasies verloor het, is dit getoon dat dit wel uitgeproke antimikrobiese aktiwiteit het teen laer konsentrasies selle. Volledige inhibisie van M. luteus groei is waargeneem vir beide die hoë digtheid sellulose en sellulose filters wat met GS en tirosidien ekstrak behandel is. Stabiliteit toetse het getoon dat die tirosidiene geadsorbeer en biologies aktief op sellulose filters bly nadat dit blootgestel is aan verskeie water was-stappe, waterwasse by verskillende temperature (25 °C -100 °C) en pH veranderinge (pH 1-12). Die antimikrobiese aktiwiteit was net beïnvloed ná blootstelling aan die water met 'n pH 13, wat moontlik is te danke aan die vatbaarheid van die CL filters by hoë pH oplosmiddels is. 'n Voorlopige studie is gedoen om die uitwerking van Trcs behandelde CL filters op die sterilisasie, ontkieming en tamatiesaailinge te bepaal. Daar is gevind dat Trcs geen effek op die ontkieming het nie, maar dat dit nie volledig die sade en omgewing steriliseer vir fungiese groei nie. Daar is egter waargeneem dat 5 μg/mL Trcs behandelde filters wortel lengte van die saailinge bevorder teenoor die giftige uitwerking soos waargeneem vir die filters wat met hoër konsentrasies Trcs behandel is. Dit word gepostuleer dat Trcs verkies om aan hidrofiliese oppervlaktes te bind wat die van die hidrofobiese aminosure en die kationiese residu van die peptied blootstel om aan die bakteriële membraan te bind om gevolglik antimikrobiese reaksie te ontlok. Die blootgestelde deel bevat sommige van die hidrofobiese residue en positiewe Orn9/Lys9 wat noodsaaklik vir die antimikrobiese aktiwiteit van die peptiede. Die hidrofobiese interaksies is veral belangrik vir die hemolitiese aktiwiteit wat tans die enigste bruikbare metode van opsporing van die geadsorbeerde Trcs is. Trcs het ook 'n tendens vir adsorpsie op sellulose en sellulose analoë wat dui op die moontlike toepassing in beskermende voedselverpakking en die beskerming van houtoppervlaktes. Trcs handhaaf hul antimikrobiese aktiwiteit, ongeag van adsorpsie aan soliede oppervlaktes. Dit kan dus afgelei word dat Trcs-behandelde soliede oppervlaktes die potensiaal het om die aanvanklike kolonisasie van bakterië te voorkom en die daaropvolgende biofilm vorming. Antimikrobiese peptied verrykde soliede oppervlaktes kan dus ontwikkel en aangepas word vir gebruik in spesifieke toepassing soos in filters, kateters en verpakkingsmateriaal.

Thesis (PhD)--Stellenbosch University, 2012. / 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. / AFRIKAANSE OPSOMMING: Vel is die grootse orgaan in die menslike liggaam en dien as buitelaag wat die gasheer se onderliggende weefsel teen infeksie beskerm. Beskadigde vel verloor egter hierdie beskermende eienskap en gee mikroörganismes die geleentheid om die liggaam binne te dring, infeksie te veroorsaak en die normale prosesse geassosieer met wondgenesing te beïnvloed. Die suksesvolle behandeling en beheer van infeksies word gedemp deur die vermoë van mikroörganismes om vinnig weerstand teen antimikrobiese middels te ontwikkel. Mikroörganismes met antimikrobiese weerstand word geredelik van pasiënte geïsoleer en dit plaas enorme druk op die gesondheidssektor. Die soeke na nuwe antimikrobiese middels en behandelings is dus van uiterste belang en sal altyd ‘n integrale rol in geneeskunde navorsing speel. Antimikrobiese peptiede (AMPe) kan moontlik as alternatief tot antibiotika dien, of kan in kombinasie daarmee gebruik word om die ontwikkeling van antimikrobiese- weerstandbiedenheid te verhoed. AMPe speel ‘n rol in ingebore beskerming en word deur soogdiere, plante, reptiele, voëls, visse en insekte geproduseer. AMPe van bakterieë (bakteriosiene), veral die van melksuurbakterieë (MSB), wek toenemende belangstelling as antimikrobiese middels vir die behandeling van bakteriële infeksies. Nanovesels, wat deur middel van ‘n elektrospin proses geproduseer word, het eienskappe wat hul aanloklik maak as wondbedekking, naamlik hoë suurstof deurlaatbaarheid, verskeie porie grottes, ‘n hoë oppervlakte tot volume verhouding, sowel as ‘n morfologiese struktuur wat die ekstrasellulêre matriks naboots. Die vermoë om ‘n verskeidenheid biologies aktiewe komponente in nanovesels te inkorporeer verhoog hul potensiaal as wondbedekkingsmateriaal. ‘n Unieke benadering is die inkorporasie van bakteriosiene van MSB in nanovesels om ‘n antimikrobiese wondbedekking te ontwikkel. In hierdie studie is die vermoë om bakteriosiene van MSB in nanovesels te inkorporeer, deur middel van ‘n mede-elektrospin proses, ondersoek. Plantarisien 423, geproduseer deur Lactobacillus plantarum 423, was suksesvol deur die mede-elektrospin proses in poliëtileen oksied (PEO) nanovesels geinkorporeer. Plantarisien 423 het na die elektrospin proses steeds sy antimikrobiese aktiwiteit behou en het die groei van Lactobacillus sakei DSM 20017T en Enterococcus faecium HKLHS geïnhibeer. Lewende selle van L. plantarum 423 was ook suksesvol deur die mede-elektrospin proses in PEO nanovesels geinkorporeer, alhoewel die lewensvatbaarheid van die selle effens afgeneem het. ‘n Nanovesel matriks is ontwikkel om die vrystelling van plantarisien 423 en bakteriosien ST4SA, geproduseer deur Enterococcus mundtii ST4SA, te beheer deur PEO en poli(D,L-melksuur) (PDLMS) in ‘n geskikte oplosmiddel te vermeng voor die elektrospin proses. Nanovesels is geproduseer wat die bakteriosiene oor ‘n verlengde tydperk kon vrystel. ‘n PEO:PDLMS (50:50) nanovesel matriks het sy stuktuur die beste behou tydens inkubasie by 37 °C en het aktiewe plantarisien 423 en bakteriosien ST4SA vrygestel. Nisien A was met dieselfde tegniek in PEO:PDLMS (50:50) geinkorporeer en nisien A, wat deur die nanovesels vrygestel was, het die groei van Staphylococcus aureus in vitro geïnhibeer. Die nisien A-bevattende nanovesel matriks het die aantal lewende selle van S. aureus noemenswaardig verminder in geïnfekteerde wonde en kon die genesing van wonde, wat nie geïnfekteer was, stimuleer. Sover ons kon vastel is hierdie die eerste gepubliseerde navorsing wat toon dat bakteriosiene, geinkorporeer in nanovesels, gebruik kan word om vel infeksies te beheer en wondgenesing te stimuleer.