Periurethral bacterial flora in women. Prolonged intermittent colonization with Escherichia coli.

To determine whether the periurethral flora of women with recurrent urinary infections differ from that of women without infection, a prospective study was conducted of matched premenopausal women. Daily or alternate-day urine cultures in patients and control subjects were obtained for six months to one year, as were daily records of sexual intercourse. Periurethral colonization with the same organism preceded 29 of 31 and six of seven episodes of significant bacteriuria in patients and control subjects, respectively. Prolonged periods of intermittent colonization with the same Escherichia coli serotype were observed in both patients and control subjects. Proportion of days of colonization of E coli or other Gram-negative bacteria was not significantly different between cases and controls and was not influenced by rates of sexual intercourse. Spontaneous cure occurred despite continued sexual intercourse.