Periurethral enterobacterial carriage preceding urinary infection.

The periurethral enterobacterial flora was identified before infective episodes in 56 patients with recurrent urinary infection. There were 91 episodes of infection, with colonisation by aerobic gram-negative bacilli in 60. In only 31 (34%) episodes were patients colonised with the infective strain. In 31 episodes there was no colonisation of the perineum and in 29 there was heterologous colonisation. In another group of 54 women investigated during an enterobacterial infection of the urine there was colonisation with the infecting organism in 55 (86%) of 64 episodes; in 2 there was no colonisation; and 7 (11%) were associated with a heterologous strain. Women who have recurrent urinary infections are susceptible to perineal and periurethral colonisation with gram-negative bacteria but the infection need not be with the colonising enterobacteria.