The periurethral aerobic flora in girls highly susceptible to urinary infections.

After the age of 5 years, normal children have but few aerobic gram-negative rods periurethrally. This study examines whether there is an abnormal periurethral colonization in urinary tract infection-prone girls during infection-free intervals, indicating a defective local defence. In 13 girls with a history of recurrent infection, daily bacterial samples were obtained from the periurethral area and from urine. Sampling continued until an infection eventually occurred. Seven girls contracted a urinary tract infection within 3-30 days. All were heavy colonized with gram-negative rods, often several species, before infection appeared. Serotyping of E. coli confirmed that it was the colonizing strain which later invaded the bladder. The findings suggest a local defect in the antibacterial defence of infection-prone individuals and gives strong evidence for ascending infection. Six girls remained uninfected during an observation period of 9-123 days. They all had a normal periurethral flora. A reasonable hypothesis would be that the same factor counteracted colonization and infection. Since abnormal periurethral colonization was not a constant phenomenon the postulated defect may vary. This might explain the fact that urinary tract infections often appear in quick succession, often followed by long infection-free intervals.