Background: Within-household transmission of extraintestinal pathogenic Escherichia coli (ExPEC) may contribute to the pathogenesis of urinary tract infection (UTI), but this is poorly understood.
Methods: A woman with acute UTI, 4 human household members who cohabited with her, and the family's pet dog underwent prospective longitudinal surveillance for colonizing E. coli for 7-9 weeks after the woman's UTI episode. Unique clones were resolved by random amplified polymorphic DNA and pulsed-field gel electrophoresis analysis. Virulence genes, phylogenetic group, and O types were defined by PCR. Comparisons with reference strains were made using random amplified polymorphic DNA profiling.
Results: Serial fecal and urine samples from the 6 household members yielded 7 unique E. coli clones (4 of which were ExPEC and 3 of which were non-ExPEC). For 3 clones, extensive among-host sharing was evident in patterns suggesting host-to-host transmission. The mother's UTI clone, which represented E. coli O1:K1:H7, was the clone that was most extensively shared (in 5 hosts, including the dog) and most frequently recovered (in 45% of samples and at all 3 time points). The other 3 ExPEC clones corresponded with E. coli O6:K2:H1, O1:K1:H7, and O2:F10,F48.
Conclusions: E. coli clones, including ExPEC, can be extensively shared among human and animal household members in the absence of sexual contact and in patterns suggesting host-to-host transmission.