Evaluation of local and systemic bovine host defense protein profiles following intramammary challenge with various strains of Staphylcoccus aureus.

摘要

Staphylococcus aureus intramammary infection is one of the leading causes of mastitis in dairy cattle. The existence of several unique strains, including small colony variants (SCV), has made the characterization of S. aureus-induced mastitis difficult, and effective treatment options are limited. Therefore, the purpose of this thesis was to investigate the local and systemic cytokine and haptoglobin responses to three different mastitis-causing strains of S. aureus (Newbould 305, Parent 3231, or Heba3231), and to resolve the milk proteome to identify potential protein biomarkers. Healthy cows were challenged with one of the three strains and their responses were measured over time. In general, the host responses were different between challenge groups, with the SCV, Heba3231, challenge group demonstrating delayed responses. Proteomic analyses of post-challenge milk samples with each strain revealed a protein, component-3 of the proteose peptone, which may have antimicrobial activities against S. aureus , and thus may be an important target for novel therapeutic strategies. These findings provide initial insight into the unique host immune response to various strains of S. aureus, including a unique bovine SCV strain associated with persistent mastitis.