An estimated $1.6 billion is spent annually on community-acquired UTIs in humans.1 Escherichia coli is the most prevalent bacterial species isolated from urine in humans and dogs with UTIs. This potential pathogen is responsible for 85% to 95% of cases of uncomplicated cystitis, > 90% of cases of uncomplicated pyelonephritis in women,2 and 44% of all UTIs in dogs.3
Most UTIs are believed to originate from the affected individual's own flora, and there are 2 theories to explain this mode of infection. The prevalence theory suggests that bacterial strains with highest prevalence in the GI tract and perineum will travel horizontally across the urogenital mucosa and ascend the distal urethra, whereas the pathogenicity theory suggests that only strains possessing certain virulence traits giving the microorganisms enhanced ability to travel, colonize, and invade the urinary tract will succeed.4,5 Molecular and epidemiologic studies of uropathogenic E coli isolates have led to additional hypotheses about the original sources of these strains, suggesting the possibility that uropathogenic E coli may be transmitted from animals to humans, either from livestock through the food chain or through contact with companion animals.
In 2001, a single clonal group of multidrug-resistant uropathogenic E coli, named clonal group A, was responsible for nearly half of community-acquired UTIs in women in multiple US states.6 The same strain was isolated from the feces of healthy human volunteers during the same period.6 One explanation was an outbreak from dissemination of contaminated food. In an epidemiologic study,7 investigators compared 495 animal and environmental E coli isolates with clonal group A isolates and found that 26% had similar molecular fingerprints when an ERIC2 PCR assay was performed, but only 1 animal isolate (from a cow) had a similar fingerprint when pulsed-field gel electrophoresis was used instead. No animal isolates in that study had virulence factor patterns or antimicrobial susceptibility patterns identical to those of human clonal group A isolates. The public-health implications of multidrug-resistant uropathogenic E coli being spread by contaminated food products would be considerable if this actually did take place.
Dogs have also been considered a possible reservoir for uropathogenic E coli on the basis of studies8–11 in which genes for similar urovirulence factors were identified, including cnf, hlyD, sfa/foc, and papGIII in E coli isolated from the feces and urine of dogs and women. These studies revealed similar virulence factors in E coli isolates from dogs and women that did not have direct or known shared environmental contact. It is hypothesized that if dogs are indeed important reservoirs of uropathogenic E coli, then that E coli isolated from the feces of dogs and owners living within the same household would have similar virulence factors.
The purpose of the study reported here was to determine the prevalence of 4 urovirulence genes (cnf, hlyD, sfa/foc, and papGIII) in E coli recovered from the feces of healthy dogs and their owners and to determine whether E coli isolates with these genes were associated with a history of UTI in either species.
Cytotoxic necrotizing factor gene
Pilus associated with pyelonephritis gene G allele III
S-fimbrial adhesin and F1C fimbriae gene
Urinary tract infection
BBL CultureSwab Plus, Becton Dickinson & Co, Sparks, Md.
MUG Fluorescence Crystals, Hach Chemical Co, Loveland, Colo.
EC Medium with MUG, Becton Dickinson & Co, Sparks, Md.
API 20E test kits, bioMérieux Inc, Durham, NC.
Fisher Scientific, Fair Lawn, NJ.
NanoDrop ND-1000, NanoDrop Technologies Inc, Wilmington, Del.
Provided by JR Johnson, University of Minnesota, Minneapolis, Minn.
Applied Biosystems, Foster City, Calif.
Amplitaq Gold polymerase, Applied Biosystems, Foster City, Calif.
Ninety-six–well PCR plates, BioRad Laboratories, Richmond, Calif.
Microseal film, BioRad Laboratories, Richmond, Calif.
iCycler, BioRad Laboratories, Richmond, Calif.
Blue/orange loading dye, Promega, Madison, Wis.
100-bp DNA ladder, Promega, Madison, Wis.
FPQuest Software, version 4.5, BioRad, Richmond, Calif.
SPSS, version 15.0, SPSS Inc, Chicago, Ill.
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