Bacteriophages (or phages) are viruses that replicate only by identifying and infecting specific host bacteria. This property has facilitated their application in microbial typing schemes, and more recently in various bacterial detection methods. However, lack of specificity and sensitivity, along with time-consuming and costly procedures have hindered their application in species-specific pathogen detection. This thesis will address these issues with regard to development of phage-based methods for the detection of 'Listeria monocytogenes, Salmonella' spp., and 'Escherichia coli'. A number of commercial and environmentally-isolated phages were first evaluated, based on host specificity ranges. Four phages were selected for further investigation, two demonstrating broad-range specificity for ' Listeria' and 'Salmonella' spp., and two exhibiting specificity for 'S. enteritidis' and non-VTEC (verotoxigenic ' E. coli') isolates. Transmission electron microscopy was used to classify each virus into a specific group based on tail length and head size, and their mode of infection was elucidated. Pathogen detection methods were chosen, based on phage properties. First, phage replication requires an actively metabolising host, making metabolic methods, including impedance, turbidimetry and colorimetry, ideal candidates for evaluation of bacteriophage behaviour. Additionally, phage lytic properties make them potentially specific biological extractants for ATP bioluminescence, which typically uses a non-specific chemical extraction. Phage-based ATP bioluminescence was successful in specifically identifying pathogens, but poor sensitivity was a problem. Filtration, increased phage exposure time and an ATP amplification method were all evaluated as means of improving sensitivity, but were limited in their application. Phage-mediated impedimetric and colorimetric methods were developed for the sensitive and specific detection and confirmation of bovine non-VTEC isolates in raw milk (<10 CFU/mL) within 12 to 16 hours. Colorimetric analysis of artificially contaminated ground beef in combination with phage AT20 was capable of confirming <1000 CFU/g of 'E. coli' G2-2. Phage-based impedimetric assays were also developed for differential detection of 'Salmonella ' spp. in skim milk powder, and 'L. monocytogenes' in raw milk. Phage-based turbidimetric pathogen assays were also demonstrated, but diluting samples to reduce initial