Objective: This study characterizes further the behavior of serologically classified isolates of Escherichia coli in women with recurrent urinary tract infections (UTIs).
Methods: A prospective, longitudinal study of 203 young to middle-aged women with UTIs was conducted. Seven hundred and sixty-one UTIs due to E. coli were identified in the 203 women during observation periods of 1.1-19.4 years. Isolates from urine were routinely serologically classified. Clusters of UTIs and rates per year of infections with the same serogroup were defined to quantify further UTIs.
Results: One hundred and forty-eight (73%) of the 203 women experienced 2-42 UTIs with E. coli. Fifteen percent of recurrences occurred within 1 month of the previous infection; 57%, 6 months; and 70%, 1 year. During the first four months, recurrences with the same serogroup accounted for 81-50% of recurrences; thereafter, recurrences with a different serogroup were more frequent. Clusters of UTIs occurred in 52% of the 148 women and ranged in size from 2-5 infections. Multiple recurrences with the same serogroup were more frequently caused by a few common serogroups.
Conclusions: Isolates of a few common serogroups of E. coli were associated with the great majority of both index and recurrent UTIs. Some isolates of both common and less common serogroups were associated with multiple recurrences with the same serogroup. The wide range in rates/year among recurrences with isolates of different serogroups in individual women were consistent with the hypothesis that these differences were more likely to be due to differences in virulence of the isolates than to host factors.