Intestinal carriage of Escherichia coli in prepubertal girls without a history of urinary tract infection was examined by collecting weekly stools and periurethral and urine samples over 3 to 4 weeks of study. Dominant and minor clones were defined by grouping 28 E. coli isolates into clonal types. Multiple enteric clones of E. coli, which changed week to week, were found in the 13 girls during the study (median, 3 clones/girl; range, 1 to 16 clones/girl). Dominance of an enteric clone did not predict persistence in the stool. In only 10 (34%) of the 29 episodes in which a dominant clone present in one weekly sample could have been detected the following week did it persist as the dominant clone in the next weekly sample. In 5 (17%) of the 29 episodes, a dominant clone found in one weekly sample was classified as a minor clone the next week. Both dominant and minor clones were observed to colonize the urinary tract. However, when colonization of the periurethra or bladder urine occurred, it was brief and often did not reflect the dominant stool flora from the same week. In fact, in only 40% of episodes was a clone that was detected either on the periurethra or in the urine also recovered from the stool the same week. Our findings suggest that the intestinal flora of healthy girls is multiclonal with frequent fluctuations in composition.Escherichia coli organisms infecting the urinary tract are thought to originate in the intestinal flora. There are two theories that attempt to explain infection of the urinary tract with E. coli derived from the intestine (12). The prevalence theory holds that the numerically dominant fecal strain is most likely to infect the urinary tract. The special-pathogenicity theory holds that a special subset of the intestinal microflora expressing specific virulence markers is most likely to infect the urinary tract. Virulence markers have been defined based on their higher frequency in E. coli isolates from patients with urinary tract infection (UTI) than among the dominant fecal strains of the UTI patient (5, 8, 13) or of healthy controls (6,7,18). Support for either theory relies on examination of the dominant strain in the stool at the time infection of the urinary tract occurs. Drawing conclusions from comparison of strains infecting the urinary tract to the dominant strain in stool is predicated on the notion that the dominant strain in an individual's stool is stable over time. The stability of dominant clones and the frequency of transfer of dominant clones to the urinary tract in healthy controls are therefore important background information for interpreting findings in patients with UTI.Few studies have examined carriage of dominant clones in the intestines of healthy controls (3,4,16). In the present study, we examined the intestinal carriage of E.coli in healthy girls without the confounding variables of antibiotic pressure, estrogenization, or sexual activity. For this, stool, periurethral, and urine samples were obtained weekly from prepubertal females. Dominant and minor ...

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Urinary tract infections (UTI) are one of the most common infections in children and symptoms may be nonspecific. The risk of renal scarring is highest in children under 1 year of age with febrile UTI and high-grade vesicoureteral reflux (VUR). Although treatment of UTI is usually straightforward, given increased rates of antimicrobial resistance worldwide, the choice of treatment for pediatric UTI should be guided by community resistance patterns whenever feasible. The benefit of antimicrobial prophylaxis after first UTI and/or in the presence of VUR remains controversial, but a recent meta-analysis supports continuous antimicrobial prophylaxis in children with VUR, indicating a need for more research in this area.