Theses and Dissertations

ORCID

https://orcid.org/0009-0005-8285-9429

Advisor

Zhang, Li

Committee Member

Sukumaran, Anuraj Theradiyil

Committee Member

Schilling, Mark Wesley

Committee Member

Dinh, Thu

Committee Member

Macklin, Kenneth

Date of Degree

5-10-2024

Original embargo terms

Visible MSU only 1 year

Document Type

Dissertation - Campus Access Only

Major

Agricultural Science (Poultry Science)

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Agriculture and Life Sciences

Department

Department of Poultry Science

Abstract

Campylobacter jejuni is microaerophilic pathogen and is one of the leading causes of acute diarrhea in the United States. Despite being a microaerophilic pathogen, C. jejuni continues to endure within the domain of food production, especially in poultry processing. In this study, we evaluated the aerotolerance, biofilm forming abilities, and genetic diversity of C. jejuni isolates previously obtained from commercial broiler processing plants. Out of 40 isolates, 25 (62.5%) were aero–sensitive (AS), 10 (25%) were intermediately aerotolerant (IAT), and 5 (12.5%) were hyper aerotolerant (HAT). The isolates belonged to four clonal complexes (CCs) and six sequence types, with the majority of isolates assigned to the CC–353 clonal complexes. Furthermore, the biofilm forming abilities of 12 field C. jejuni isolate on stainless-steel coupons were measured using a crystal violet assay by measuring the optical density (OD600) and viable cell count was enumerated using direct plating. A notable interaction between aerotolerance categories and temperature (P < 0.039) impacting the number of biofilm-attached C. jejuni cells on stainless steel coupons. All isolates had greater counts when incubated at 42ºC compared to room temperature, regardless of oxygen level (P < 0.001). Furthermore, stronger biofilm density was observed at 42°C compared to room temperature, regardless of oxygen level. Eight C. jejuni strains including 3 AS, 3 IAT, and 2 HAT were used to understand the genomic characterization that underlies aerotolerance and biofilm formation in C. jejuni using whole-genome sequencing (WGS). Genes associated with aerotolerance, and biofilms were present in all eight isolates despite the phenotypic differences. The virulence genes associated with Type VI secretion system (T6SS) and VAS effector proteins were unique in aerotolerant isolates. Antimicrobial resistance markers related to antibiotic efflux pumps, beta-lactams, fluoroquinolones, tetracycline, aminoglycosides, and streptothricin were identified. In conclusion, this study elucidates the diverse aerotolerance profiles and genetic characteristics of C. jejuni isolates from poultry processing plants, shedding light on their ability to persist despite environmental stresses. Additionally, the biofilm forming ability at different temperatures emphasizes the importance of targeted interventions to mitigate its impact on food safety.

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