Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Comparative and Experimental Medicine

Major Professor

Joseph Bartges

Committee Members

David Bemis, Ann Draughon, Karla Matteson


Contact between human beings and dogs may allow sharing of antimicrobial resistant and virulent bacteria. Objectives of this study were to determine the prevalence of cross-species sharing of fecal E. coli based on pulse field gel electrophoresis (PFGE) profile similarity, to compare antimicrobial susceptibility patterns and virulence factor patterns between dog-owner pairs, and to analyze the epidemiology of cross-species sharing using a questionnaire.

A cross-sectional study comparing fecal E. coli isolates from dogs and their owners was conducted. A questionnaire and fecal sample was collected from 61 dogowner pairs and 30 controls. Three E. coli colonies were isolated from each participant and confirmed biochemically. Antimicrobial susceptibility of each isolate was determined via disc diffusion for 17 antimicrobial agents routinely monitored by the National Antimicrobial Resistance Monitoring System. PFGE profiles were used to establish relatedness among bacterial isolates. A multiplex PCR was developed to determine presence or absence of 4 urovirulence factor genes: cnf, hlyD, sfa, and papGIII. The questionnaire asked about medical history, antimicrobial therapy, hygiene, and relationship with dog.

A wide array of PFGE profiles was observed in E. coli isolates from all participants. Within-household sharing occurred with 9.8% prevalence, and acrosshousehold sharing occurred with 0.26% prevalence. No specific behaviors were associated with increased clonal sharing between dog and owner.

No differences were found in susceptibility results or virulence factor patterns between dog-owner pairs. Control isolates were more resistant than canine isolates, and human beings carried more multiple-drug resistant E. coli than dogs. Isolates from owners who did not wash their hands after petting their dogs had increased resistance to ampicillin. An association was found in women between history of UTI and presence of each virulence factor in their dog’s fecal E. coli. Antimicrobial resistance was associated with reduction of virulence factors.

Within-household sharing of E. coli occurred more commonly than acrosshousehold sharing, but both direct contact and environmental reservoirs may be important routes for cross-species sharing of bacteria and genes for resistance and virulence. Cross-species bacterial sharing is a potential public health concern, and good hygiene is recommended.

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