The periurethral aerobic bacterial flora in healthy boys and girls.

The present study was undertaken to provide information about the presence of bacterial flora in the periurethral region of healthy children and its variation with age and sex. It was intended as a basis for subsequent studies in individuals prone to urinary tract infection. Quantitative methods were used for bacteria sampling and culture. The study included 394 girls and 305 boys from birth to 16 years. During the first few weeks of life a massive aerobic bacterial flora (E. coli, enterococci, staphylococci) was established in the periurethral region of both sexes. The colonization with E. coli and enterococci began to diminish already during the first year of life and became very scanty after the age of 5 years. In newborns E. coli colonization was dense in boys and scanty in girls. Later E. coli was the dominating gram-negative species in girls of all age groups. In boys E. coli dominated during the first half year of life, later Proteus was as common as E. coli; staphylococci did not change very much. Urine samples from healthy school-children contained very few gram-negative bacteria; even when collected without preceding cleansing. The results suggest that there might be a local defence mechanism maturing during the first year of life, eventually protecting the exposed area from colonization with gram-negatives and enterococci.