Dissertation
Proper identification of coagulase-negative staphylococci (CNS) isolated from bovine intramammary infections (IMI) and characterization of their virulence factors
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2009
DOI:
https://doi.org/10.7273/000006177
Abstract
Coagulase-negative staphylococci (CNS), a heterogeneous group of more than 30 Staphylococcus spp., are the most prevalent pathogens isolated from bovine intramammary infections (IMI). Although they have been considered minor mastitis pathogens, bovine IMI by CNS cause a negative economic impact on the dairy industry by adverse change in milk quality and reduced milk production. Accurate and proper identification of CNS is a prerequisite for understanding of the full nature of the CNS. A proposed genotypic method in this study, PCR-restriction fragment length polymorphism (PCR-RFLP) of the gap gene (gap PCR-RFLP) was compared with a phenotypic method, API STAPH ID 20, a commercially available identification system for the speciation of CNS isolates from bovine IMI. We speciated 263 CNS isolates from bovine IMI by partial 16S rRNA gene sequence analysis as the definitive test. The gap PCR-RFLP analysis appears to be a more accurate and cost effective than phenotypic methods suggesting the gap PCR-RFLP analysis could be an alternative speciation method for CNS isolates from bovine IMI. The virulent characteristics of CNS isolates from bovine IMI have not been fully understood. In this study, we investigated extensively the virulent properties of CNS isolates from bovine IMI associated with pathogenic responses regarding, 1) ability to adhere and invade bovine mammary epithelial cells (MAC-T cells), as well as adherent properties to extracellular molecules (ECM) such as fibronectin (Fn) and collagen (Cn), 2) the possession of genes encoding staphylococcal superantigens (SAgs), and 3) the association between these virulence characteristics and linear somatic cell counts (LSCC), an indicator of pathogenic responses in bovine mammary gland. The current study indicates that 1) a relatively high proportion of these isolates had the ability to invade MAC-T cells, 2) the presence of Cn adherence ability is significantly associated with the ability to invade or adhere to MAC-T cells, and a greater inflammatory response in vivo as determined by increased LSCC, and 3) the presence of SAg genes in CNS isolates from bovine IMI was not associated with an elevation of LSCC. This suggests that Cn adherence could be potential virulent characteristics of CNS in bovine IMI.
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Details
- Title
- Proper identification of coagulase-negative staphylococci (CNS) isolated from bovine intramammary infections (IMI) and characterization of their virulence factors
- Creators
- Joo Youn Park
- Contributors
- Lawrence Kenneth Fox (Chair)William Sischo (Committee Member) - Washington State University, UNKNOWNFred R Rurangirwa (Committee Member)Gregory A Bohach (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- College of Veterinary Medicine
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 132
- Identifiers
- 99901055122901842
- Language
- English
- Resource Type
- Dissertation