Date of Completion

2019

Document Type

Honors College Thesis

Department

Animal and Veterinary Sciences

Type of Thesis

Honors College

First Advisor

John Barlow

Keywords

mastitis, teat skin, somatic cell count (SCC), growth antagonism, Staphylococcus aureus

Abstract

Many studies suggest that certain potentially beneficial commensal bacteria residing in the teat skin environment may protect the bovine mammary gland from mastitis by actively inhibiting colonization by major mastitis pathogens. To investigate the contribution of these commensals to differences in susceptibility to mastitis observed between healthy cows and chronically infected cows, teat skin swab samples were collected from 8 mature, lactating Holstein cows – 4 animals having demonstrated consistently low somatic cell counts and 4 animals having demonstrated consistently high somatic cell counts – and screened for the presence of organisms demonstrating antagonism against the major mastitis pathogen Staphylococcus aureus. Presumptive antagonists identified were also individually tested against a second S. aureus strain to confirm inhibition. 130 isolates total were characterized as S. aureus antagonists over the course of this study, and 36 representative isolates were selected for 16S rRNA sequencing to establish species identity. While the original hypothesis was not supported by the data, potential flaws in study design that may have influenced the results were identified and used to pinpoint targets to address through further investigation. Ultimately, this study did support the idea that the bovine teat skin microbiota represents a rich source of Bacillus and Paenibacillus commensals demonstrating effective S. aureus antagonism which, via the purification of antimicrobial substances and/or the development of novel probiotics, could potentially be applied to alternative strategies of mastitis control.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Available for download on Friday, May 15, 2020

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