Dogs as reservoirs of Escherichia coli strains causing urinary tract infection in their owners

It is known that humans and pets living together can share the same Escherichia coli strain. In this study we assessed the role played by household pets as reservoirs of E. coli strains causing urinary tract infection (UTI) in their owners. Fecal swabs from 15 dogs and six cats living with 19 patients with community-acquired E. coli UTI were screened by antimicrobial selective plating to detect E. coli displaying the same susceptibility profile of the UTI-causing strain. Pet/patient pairs sharing strains with indistinguishable susceptibility and pulsed-field gel electrophoresis (PFGE) profiles were quantitatively screened for fecal carriage of the UTI-causing strain approximately 10 months later using bacterial counts on selective agar supplemented with the relevant antibiotics. Isolates from both time points were characterized by whole-genome single nucleotide polymorphism (SNP) analysis. PFGE revealed indistinguishable E. coli within two (11%) pet/patient pairs. In pair A, the UTI-causing strain was detected 10 months later in both the patient (108 CFU/g) and her dog (104 CFU/g). In pair B, only the dog was colonized with the UTI-causing strain upon re-sampling (105 CFU/g), indicating dog-to-man transmission. For both pairs, less than 70 SNPs distinguished any isolate from the first and second sampling. The study shows regular co-carriership of UTI-causing E. coli strains between humans and their pets, and indicates that dogs can be a source of human infection. Although final evidence for transmission is lacking, hygiene precautions should be considered by people fraternizing pets. This may be particularly relevant for persons with a compromised immune system.