Date of Graduation

5-2015

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Kristen E. Gibson

Committee Member

Steven C. Ricke

Second Committee Member

John A. Marcy

Abstract

Staphylococcus aureus is one of the most important pathogens, causing various diseases in humans and animals. In addition, S. aureus is a common foodborne pathogen. As methicillin- resistant S. aureus (MRSA) becomes increasingly prevalent, controlling this pathogen in animals and humans with standard antibiotic treatment has become challenging. Combinations of different antimicrobial agents represent one of the most promising approaches for combating multidrug - resistant bacteria both for treatment of clinical disease as well as in food. Two such antimicrobials with potential application in the food industry include essential oils (EO) and host-specific bacteriophage (phage). The objectives of this study were 1) to determine the efficacy of varying concentrations of pure EOs compounds against S. aureus and 2) to evaluate the efficacy of a S. aureus-specific bacteriophage against 4 strains of S. aureus. The overall goal was to combine these antimicrobials to determine potential synergism and possible application for the control of S. aureus on raw chicken products. Four EO compounds were evaluated by disc diffusion assay to determine inhibitory effects against five strains of S. aureus. Next, a growth inhibition assay was performed using a 96-well plate bioassay to measure change in optical density over a 48-hour period. Phage adsorption assays were performed up to 120 h at 6, 13, and 37°C to determine lytic activity. The results from disc diffusion, growth inhibition, and phage adsorption assays indicate that EO compounds and bacteriophage can be used as antimicrobials against S. aureus. For application in the food industry, these antimicrobials were evaluated for their efficacy against S. aureus on raw chicken pieces at 6, 13, and 25°C. Results indicate that at 25°C phage K alone inhibits S. aureus growth better as compared to other antimicrobial combination. At 6 and 13°C, there was no significant effect of EO and phage alone or in combination against S. aureus when applied on the raw chicken pieces. Therefore, for these antimicrobials to work in vivo such as raw meat products, a better delivery method should be employed for a uniform application on meat.

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