Theses and Dissertations

Issuing Body

Mississippi State University


Zhang, Li

Committee Member

Sukumaran, Anuraj Theradiyil

Committee Member

Adhikari, Pratima

Committee Member

Kiess, Aaron S.

Date of Degree


Document Type

Graduate Thesis - Campus Access Only


Poultry Science

Degree Name

Master of Science (M.S.)


College of Agriculture and Life Sciences


Department of Poultry Science


Avian pathogenic Escherichia coli (APEC) is the causative agent of colibacillosis. APEC causes significant economic losses to the poultry industry. In this study, 66 E. coli isolates were collected from broiler flocks across Mississippi and categorized as clinical and non-clinical isolates. Genotypic and phenotypic characterization of virulence factors and antimicrobial resistance profiles of these E. coli were examined. The data disclosed a higher prevalence of virulence genes in clinical isolates than in non-clinical isolates. High differences on the genotypic and phenotypic antimicrobial resistance among clinical and non-clinical isolates were observed. Whole genome sequences of avian E. coli elaborated a diverse range in genetic composition, phylogenic relationship, antimicrobial resistance, and virulence gene profiles. Collectively, the results showed that the virulence factors and phenotypic characteristics of APEC may play a role in the pathogenesis of avian colibacillosis. Therefore, this study provides insight to understand the epidemiological background, microbial behavior, and pathogenesis of APEC.