Effect of periurethral colonization on the risk of urinary tract infection in healthy girls after their first urinary tract infection

Abstract

We examined whether periurethral colonization with bacterial pathogens predicts recurrent urinary tract infection (UTI) in girls at risk for infection. Periurethral and urine cultures were obtained weekly from each of seven healthy toilet-trained girls (3 to 6 years of age, normal urinary tract) during the 6 months after their first UTI, when the risk of UTI is 35%. Periurethral and urine isolates of Escherichia coli were grouped into electrophoretic types (ETs) by multilocus enzyme electrophoresis. Fifty-three (43%) of the 122 periurethral cultures were positive for a pathogen (median, 6 positive cultures/patient). Two patients each experienced 2 UTI. Positive periurethral cultures were as common in the five uninfected patients as in the two infected patients (9 of 32 vs. 44 of 90, P = 0.06). In only 1 of the 4 UTI was the infecting organism detected on the periurethra in the 2 weeks prior. Multilocus enzyme electrophoresis of the 104 periurethral and urine E. coli isolates from the 7 patients revealed 22 ETs. Such a diversity of ETs suggests that the flora of the periurethral region is colonized by multiple E. coli strains and is constantly changing in clonal composition. Five E. coli strains (ETs) associated with the initial UTI were detected again on the periurethra of 3 patients during surveillance but did not ascend to cause infection. Thus the mere presence of a pathogen on the periurethra is not by itself a risk factor for UTI.