Date of Graduation

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor

Dan J. Donoghue

Committee Member

Annie M. Donoghue

Second Committee Member

Casey M. Owens

Third Committee Member

Charles F. Rosenkrans, Jr.

Keywords

antibiotic alternative, Campylobacter jejuni, carvacrol, human campylobacteriosis, postharvest, poultry

Abstract

Campylobacter jejuni, a leading cause of bacterial gastroenteritis worldwide, is strongly associated with the consumption and/or mishandling of raw contaminated poultry products. Thus, interventions aiming to reduce C. jejuni counts on poultry products could greatly reduce the incidence of human campylobacteriosis. In the first study, the efficacy of a generally recongnized as safe (GRAS) compound, carvacrol (CR; derived from oregano oil), as an antimicrobial wash treatment to reduce C. jejuni on chicken skin was evaluated. Three delivery systems of CR: suspension, emulsion and nanoemulsion were used. C. jejuni counts were reduced up to 4 log10 cfu/sample by 2% dose of CR suspension at 0 h (P < 0.05). Carvacrol emulsion or nanoemulsion did not show any additional reduction in C. jejuni counts when compared to suspension.

In the second study, the efficacy of gum arabic (GA) or chitosan (CH) coatings fortified with CR to reduce C. jejuni on chicken wingettes was investigated as an additional intervention to increase the antimicrobial activity of CR. Inoculated chicken wingettes (~7.5 log10 cfu of C. jejuni/sample) were randomly assigned to baseline, control (0%), CR (0.25, 0.5 or 1%), GA (10%), CH (2%) or their combinations. After 1 min of coating, wingettes were air dried (1 h) and sampled at days 0, 1, 3, 5, and 7. All three doses of CR, CH or GA-based coating fortified with CR reduced C. jejuni from day 0 through 7 by up to 3.0 log10 cfu/sample (P < 0.05). Moreover, the antimicrobial efficacy of GA was improved by CR and the coatings reduced C. jejuni by ~1 to 2 log10 cfu/sample at day 7. In addition, CH-CR coatings reduced total aerobic counts on majority of storage time when compared with baseline. No significant difference in the color of chicken wingettes was observed between treatments. Exposure of this pathogen to sublethal concentrations of CR, CH or combination significantly modulated select genes encoding for energy taxis, motility, binding and attachment. The results suggest that GA or CH-based coating with CR could potentially be used as a natural antimicrobial to control C. jejuni in post-harvest poultry products.

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