Mannheimia haemolytica is the principal bacterial agent associated with bovine respiratory disease (BRD). It has a significant economic impact on the beef feedlot industry. The current methods for BRD prevention and treatment have various problems and limitations, especially with reports of increased antimicrobial resistance in M. haemolytica. Bacteriophage therapy presents a novel method to mitigate M. haemolytica. This study aimed to isolate strictly lytic M. haemolytica-specific bacteriophages from bovine nasopharyngeal swabs and feedlot trough water. This was accompanied by an extensive characterization of temperate bacteriophages induced from representative strains of a M. haemolytica collection. Phage morphology, host specificity, genomic diversity, and comparative genomics were determined. Even though temperate bacteriophages are not ideal candidates for phage therapy, they can be engineered or modified to serve this function. Genome sequences of selected temperate bacteriophages also provide a foundation for future studies on the biology of these microorganisms. / viii, 107 leaves : ill. ; 29 cm

Mannheimia haemolytica is an opportunistic pathogen in cattle and the main bacterial agent in bovine respiratory disease. Despite its economic importance, few studies have characterized the genetic diversity of M. haemolytica, particularly from feedlots. Three genotyping techniques (BOX-PCR, (GTG)5-PCR and PFGE) were compared to discriminate M. haemolytica and strains from the family Pasteurellaceae. PFGE was the most discriminating and repeatable, although BOX-PCR was most accurate in clustering isolates together according to species. Mannheimia haemolytica was isolated from nasal swab samples collected from cattle upon entry and exit from two feedlots in southern Alberta. These were characterized by PFGE and antimicrobial susceptibility using a disk-diffusion assay. Select gene determinants were screened for using PCR. PFGE analysis revealed the isolates to be highly diverse. Ten percent of the isolates exhibited resistance. At present, the development and spread of antimicrobial resistance in M. haemolytica observed within the feedlots examined appears to be low. / xi, 116 leaves : ill. ; 29 cm