Date of Award

2004

Document Type

Master Thesis

Degree Name

Masters of Science (Research)

Department

Biological Sciences

First Advisor

Dr. Aidan Coffey

Abstract

This study describes firstly, the assembly of a collection of a varied spectrum of staphylococci which can be used to test the efficacy of bacteriophages for the biocontrol of problematic members of this genus. The collection assembled includes a variety of multi-antibiotic resistant MRSA (methicillin resistant S. aureus) strains, hVRSA (hetero vancomycin resistant S. aureus), VRSA and also teicoplenin resistant isolates. It also included a broad range of species of coagulase-negative {non-aureus) staphylococci including S. caprea, S. haemolyticus, S. saprophyticus, S. epidermidis, S. chromogenes, S. capitis, S. hominins and S. hyicus. All strains were characterized by morphology on Baird Parker, coagulase, antibiotic resistance profile (using twelve antibiotics) and Random Amplified Polymorphic DNA (RAPD) profiles. Secondly the study succeeds in bringing together and characterizing a group of phages, which successfully eliminate various members of the staphylococci assembled. These are phage CSl, phage DW2 and phage K. It was verified that phage K has an unusually broad host range in that its specificity extends beyond S. aureus to include many other species. In the course of the study, it was shown that certain MRSA strains exhibited a high degree of insensitivity against phage K. A natural method was therefore devised whereby the host range of phage K could be broadened to successfully form clear plaques on these insensitive strains. This was based on the principle of classical phage DNA modification to circumvent restriction activity in the insensitive MRSA strains. It was shown that when phage K was modified to become capable of plaque formation on one previously-insensitive strain, it could also lyse a significant number of additional MRSA strains. Finally, phage K was incorporated into a model hand-wash solution where it was repeatedly evaluated for its efficacy in reducing S. aureus numbers on human skin. Application of the hand wash conclusively resulted in a 90% reduction in number of S. aureus on human skin. This latter application may well have beneficial uses in hospitals.

Access Level

info:eu-repo/semantics/openAccess

Download

Included in

Microbiology Commons

Share

COinS