University of SaskatchewanHARVEST
  • Login
  • Submit Your Work
  • About
    • About HARVEST
    • Guidelines
    • Browse
      • All of HARVEST
      • Communities & Collections
      • By Issue Date
      • Authors
      • Titles
      • Subjects
      • This Collection
      • By Issue Date
      • Authors
      • Titles
      • Subjects
    • My Account
      • Login
      JavaScript is disabled for your browser. Some features of this site may not work without it.
      View Item 
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item

      Using comparative genomics to identify virulence traits and vaccine candidates in Mannheimia haemolytica

      Thumbnail
      View/Open
      KLIMA-DISSERTATION.pdf (3.772Mb)
      Date
      2015-08-13
      Author
      Klima, Cassidy
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
      Show full item record
      Abstract
      Bovine respiratory disease (BRD) is the principal cause of morbidity and mortality among feedlot cattle. Mannheimia haemolytica is consistently implicated in this condition, but treatment options are diminishing with the rise of antimicrobial resistance and intensifying consumer pressure to reduce reliance on conventional therapies. Thus, sustainable alternatives like vaccination are required. In this study, the phenotypic and genotypic diversity of BRD pathogens were examined with the objective to identify vaccine targets using reverse vaccinology, an innovative approach to identify antigens via genomic sequence. Preliminary surveillance confirmed M. haemolytica serotype 2 isolates were predominant in healthy animals (75.5%) while serotypes 1 (70.7%) and 6 (19.5%) were common in diseased animals. Pathogens of BRD, including M. haemolytica, Pasteurella multocida and Histophilus somni were also isolated from North American BRD mortalities, and compared using pulsed-field gel electrophoresis and antimicrobial susceptibility. Concurrently, polymerase chain reaction detection of bacterial and viral agents confirmed that M. haemolytica with bovine viral diarrhea virus were the most prevalent. Whereas isolates from live cattle were found to have a relatively low level of resistance, several pathogens from the mortalities were found to contain integrative conjugative elements (ICE) conferring resistance to seven antimicrobial classes. These ICEs were transferred via conjugation to other bacterial species, emphasizing the need for alternative antimicrobial therapies. Collectively, data from these investigations informed the selection of 11 diverse M. haemolytica strains for whole genome sequencing and comparative analyses. Several bacteriophage associated genes and CRISPR-Cas regulated gene expression systems were identified and are likely contributing to virulence in M. haemolytica. Coding sequences across all genomes were screened using pan-genome analysis, identifying 291 candidates with cell-surface associated signatures. Using a cell-free translation system and enzyme-linked immunosorbent assay the candidates were screened against serum from cattle challenged with serovar 1, 2 or 6 of M. haemolytica, and ranked according to immunogenicity. The top five vaccine candidates included Ssa1, ComE, a solute binding protein, an outer membrane protein, and the periplasmic component of an ABC transporter. With further characterization, these unique antigenic candidates could be developed into a vaccine to effectively reduce the dependence on antimicrobial therapies.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Large Animal Clinical Sciences
      Program
      Biology
      Supervisor
      McAllister, Tim; Hendrick, Steve
      Committee
      Potter, Andrew; Alexander, Trevor; Penner, Gregory
      Copyright Date
      June 2015
      URI
      http://hdl.handle.net/10388/ETD-2015-06-2118
      Subject
      bovine respiratory disease
      antimicrobial resistance, reverse vaccinology, integrative conjugative elements, Mannheimia haemolytica, feedlot cattle
      Collections
      • Graduate Theses and Dissertations
      University of Saskatchewan

      University Library

      © University of Saskatchewan
      Contact Us | Disclaimer | Privacy