Thesis (PhD)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Bacterial resistance against antibiotic treatments is a global concern and resistance to almost every known antibiotic has already been reported. There is thus a significant need for the development of novel antimicrobial drugs.
In addition to probiotic traits, certain bacteria have the ability to produce antimicrobial peptides, referred to as bacteriocins. Lantibiotics, a group of small ribosomally synthesized bacteriocins, recently gained interest for their application in the medical field. Lantibiotics have a very specific structure, including lanthionine rings, that stabilise the peptides. Due to their small size and specific action, these peptides reach specific sites of infection without affecting the composition of the host’s natural microbiota. As with any therapeutic agent, antimicrobial peptides are also prone to in vivo degradation, binding, clearance via immune action and development of bacterial resistance.
Nisin F, a class Ia lantibiotic produced by Lactococcus lactis subsp. lactis F10, has already shown activity against the well-known pathogens Stapylococcus aureus, Listeria monocytogenes and various antibiotic resistant strains. The aim of this study was to assess the antimicrobial activity of nisin F against systemic S. aureus infections in mice and possible immune responses elicited by the peptide.
A single administration of nisin F to the peritoneal cavity protected mice from S. aureus infection for at least 15 min. After continuous administration, the peptide showed no significant antimicrobial activity against S. aureus. The peptide did, however, convey some degree of protection to infected mice by stimulating a pro-inflammatory action through lymphocyte protection. When administered to uninfected mice, nisin F had an immune boosting effect via interleukin (IL)-6 and IL-10 without being detrimental to the host. The ex vivo effects of nisin F was compared to nisin A, a natural nisin variant, and Nisaplin®, a commercially purified form of nisin A. None of the three peptides inhibited the functional capacity of leukocytes in terms of 1L-1β en IL-6 production, not even in the presence of an external stimulus (lipopolysaccharides from Escherichia coli). Cytotoxicity was detected in response to high dosages of nisin F. Serum inhibited the antimicrobial effect of nisin F and nisin A, but Nisaplin® remained unaffected.
Nisin F was applied against systemic infection for the first time and the immunological effect of the peptide was investigated. Nisin F partially protected mice against S. aureus infections through immunomodulatory effects. This study provided valuable knowledge on the in vivo application of nisin F. With further optimization of nisin F preparation and application systems, the peptide might be more effective against in vivo infections. / AFRIKAANSE OPSOMMING: Bakteriële weerstand teen antibiotika wek wêreldwyd kommer en weerstand teen amper elke bekende antibiotikum is reeds aangemeld. Daar is dus 'n groot behoefte vir die ontwikkeling van nuwe antimikrobiese middels.
Bykomend tot probiotiese eienskappe, het sekere bakterieë die vermoë om antimikrobiese peptiede, bekend as bakteriosiene, te produseer. ‘n Groep klein ribosomaal-gesintetiseerde bakteriosiene, lantibitiotika, is onlangs vir mediese toepassing oorweeg. Lantibiotika beskik oor 'n baie spesifieke struktuur, insluitend lantionien ringstrukture, wat die peptied stabiliseer. Weens hul klein grootte en spesifieke aksie is hierdie peptiede daartoe in staat om spesifieke areas van infeksie te bereik sonder om die gasheer se natuurlike mikrobepopulasie te beïnvloed. Soos met enige terapeutiese middel, is bakteriosiene ook geneig tot in vivo afbreking, binding, klaring via die immuunsisteem en ontwikkeling van bakteriële weerstand.
Nisien F, 'n klas Ia lantibiotikum, deur Lactococcus lactis subsp. lactis F10 geproduseer, het reeds aktiwiteit teen die bekende patogene Stapylococcus aureus, Listeria monocytogenes en verskeie antibiotika-weerstandige stamme getoon. Die doel van hierdie studie was om die antimikrobiese aktiwiteit van nisien F teen sistemiese S. aureus infeksies in muise te bepaal, asook die moontlike immuunreaksies wat die peptied mag veroorsaak.
'n Enkele toediening van nisien F het muise vir ten minste 15 min teen S. aureus beskerm. Na deurlopende administrasie het die peptied geen beduidende antimikrobiese aktiwiteit teen S. aureus getoon nie. Die peptied het egter 'n mate van beskerming aan geinfekteerde muise verleen deur ‘n pro-inflammatoriese aksie te inisieer deur limfosiet beskerming. Met toediening aan gesonde diere, het nisien F 'n immuunversterkende effek teweeg gebring via interleukin (IL)-6 en IL-10 vlakke, sonder nadelige uitwerking op die gasheer. Die ex vivo effek van nisien F is ook vergelyk met nisien A, 'n natuurlike variant van nisien, asook Nisaplin®, 'n kommersieël-gesuiwerde vorm van nisien A. Nie een van die drie peptide het leukosiete se funksionele kapasiteit in terme van 1L-1β en IL-6 produksie inhibeer nie, selfs nie in die teenwoordigheid van ‘n eksterne stimulus (lipopolisakkariede van Escherichia coli) nie. Seltoksisiteit is na blootstelling aan hoë dosisse van nisien F waargeneem. Serum het die antimikrobiese effek van beide nisien F en nisien A geïnhibeer, terwyl die werking van Nisaplin® nie beïnvloed is nie.
Nisien F is vir die eerste keer teen sistemiese infeksies ingespan en die immunologiese impak van die peptied is ondersoek. Nisien F het gedeeltelike beskerming aan muise met S. aureus infeksies verleen deur die immuunsisteem te versterk. Die resultate het ‘n waardevolle bydrae gelewer tot die in vivo toediening van nisien F. Met verdere optimisering van nisien F voorbereiding en toedieningsisteme, mag die peptied moontlik meer effektief teen in vivo infeksies aangewend word. / The National Research Foundation (NRF) of South Africa for financial support and funding of the research
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/79873 |
| Date | 03 1900 |
| Creators | Brand, Anneke Mari |
| Contributors | Dicks, Leon Milner Theodore, Smith, Carine, Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Format | ix, 117 p. : col. ill. |
| Rights | Stellenbosch University |
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