Date of Award


Document Type

Master Thesis

Degree Name

Masters of Science (Research)


Biological Sciences

First Advisor

Dr Máire Begley

Second Advisor

Dr Jim O'Mahony

Third Advisor

Dr Hugh O'Donnell


Antimicrobial resistance has evolved into being one the major threats facing clinical environments worldwide. It has led to the deerease in effective prevention and treatment of pathogenic bacteria. One such bacterium is Staphylococcus epidermidis. Once considered a relatively harmless and commensal baeterium, it has recently evolved into being one the leading eauses of nosocomial infections. S. epidermidis has proven hamiful due to its ability to fonn detrimental biofilms. Biofilms are structured eonsortia of bacteria embedded in a self-produced polymer matrix that allows adherence to biotic or abiotic surfaces. These biofilms have played a leading role in healthcare-acquired infections with particular emphasis on patients with indwelling medical devices such as urinary and intravascular catheters, and orthopaedic devices such as hip and knee implants. Biofilms are inherently refraetory to treatment with antibiotics making them difficult to eradicate, which in turn can lead to infections, malfunction and removal of the device. Medieal device-related infections are a public health concern and an economic burden, for example some European countries see 1000 deaths per year and ensuing eosts of 35-164 million euros per year. This study investigated the potential of the natural antimicrobial agent called nisin - a bacterially derived antimicrobial peptide whieh is of generally recognised as safe (GRAS) status and its bioengineered derivatives (M17Q and M21A). This study examined and answered three eore questions. One, nisin A prevents and controls biofilm from occurring on plastic, stainless steel, polyvinyl chloride and polyvinyl resin biomaterials. Two, the combination of nisin A and conventional antibiotics work better at preventing and treating biofilms on plastic materials, and three, nisin derivatives showed a positive indication that they work better than nisin A wildtype in the prevention of S. epidermidis biofilms on a range of materials. The results have demonstrated the potential benefits of including nisin as a viable option in the treatment of S. epidermidis biofilms in a clinical setting.

Access Level


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Biology Commons