Date of Award

2011

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Prof R. Paul Ross

Second Advisor

Dr Olivia McAuliffe

Third Advisor

Dr Aidan Coffey

Abstract

The objective of this thesis was lo evaluate the potential of bactcriophages e4/1 c and cl 1/2 ns biocontrol agents for E. coli O157:H7. Initially, e4/lc and el 1/2 were subjected to high-throughput 454 sequencing. The data generated revealed that e4/I c (47,112 bp) is very similar to the lytic E. coli phages RTP and JK06. Interestingly, differences within the tail module led to the identification of a putative site of attachment to E. coli O157:H?. Comparative genomic analysis indicated that el 1/2 (168,470 bp) is a novel member of the T-even group, with high degrees of similarity to T4 but with tail proteins similar to phages PP0I and ARI, both E. coli O157:H?specific phages. Significantly, no virulence genes or integration factors were detected in either phage, features that could preclude them from use as biocontrol agents. To assess the potential of the phages as biocontrol agents, their efficacy was assessed under conditions relevant to the food chain environment. Subsequently, the use of a cocktail of e4/lc and el 1/2 to reduce E. coli O157:H? on the hide surface of cattle was evaluated and a significant reduction (p<0.05) of E. coli O157:H? numbers were observed. Furthermore, the ability of e4/lc and el 1/2 to reduce E. coli O157:H7 numbers in a model rumen system and in experimentally inoculated animals was investigated. In the ex vivo rumen model, the numbers of E. coli O157:H? was significantly (p<0.05) reduced to below the limit of detection within I h in the presence of el 1/2. Reductions in pathogen number were also observed in the presence of e4/l c, although not to the same extent. In the experimentally-inoculated cattle, E. coli O157:H? numbers rapidly declined in all animals within 24-48 hrs; however, there was no significant (p>0.05) difference between the phage treated or control animals.

Access Level

info:eu-repo/semantics/openAccess

Download

Included in

Microbiology Commons

Share

COinS