Title page for ETD etd-11192001-144315


Type of Document Dissertation
Author Altekruse, Sean Fitzgerald
Author's Email Address altekrus@mail.nih.gov
URN etd-11192001-144315
Title Characterization of Climical and Commensal Escherichia coli Isolates from an Integrated Turkey Operation
Degree PhD
Department Veterinary Medical Sciences
Advisory Committee
Advisor Name Title
Elvinger, Francois C. Committee Chair
Eifert, Joseph D. Committee Member
Karunakaran, Daniel Committee Member
Pierson, Frank William Committee Member
Sriranganathan, Nammalwar Committee Member
Keywords
  • Avian Pathogenic Escherichia coli
  • Antimicrobial resistance
Date of Defense 2001-10-26
Availability unrestricted
Abstract
Pathogenic E. coli infections cause approximately one quarter of disease losses in commercial turkey flocks. A small subgroup of E. coli causes most infections. Epidemiologic studies of this disease have been hindered by a lack of reliable markers to discriminate between pathogenic and fecal E. coli and by the diversity of poultry strains. Reliance on antimicrobials to control E. coli infections has caused widespread antimicrobial resistance.

One hundred five clinical E. coli were obtained, and 1104 isolates were collected from fecal specimens of 20 flocks in an integrated turkey operation. Biochemical fingerprinting and antimicrobial susceptibility tests were performed on all isolates, and somatic antigen serologic testing and PCR for potential virulence genes were conducted on 299 strains including all clinical isolates and fecal isolates that had similar traits to clinical isolates. Most avian E. coli infections were caused by a few clonal strains that were uncommon in normal fecal flora. The potential virulence genes iss, K1 and tsh were detected more frequently among clinical than fecal isolates; however, the pattern of occurrence did not suggest that these genes were useful markers for identifying pathogenic strains.

Syndromes consistent with colibacillosis were the most commonly reported illness and principal rationale for antimicrobial therapy in sampled flocks. Most clinical E. coli isolates were resistant to gentamicin, sulfamethoxazole and tetracycline. Although resistance to fluoroquinolones and β-lactam antibiotics occurred less frequently, the potential for resistance to emerge to these antimicrobials was evident. A Bayesian model to estimate sample size confirmed the diversity of avian fecal E. coli strains.

Studies are needed to define risk factors for infection with and identify markers for avian pathogenic E. coli strains. These research priorities are complementary and may lead to the identification of new interventions to prevent this important infectious disease of poultry.

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