Most previous studies have shown that the digestive tract of the neona
te is rapidly and heavily colonized in the first few days of life, but
all the studies so far used either feces or rectal swabs to isolate a
nd identify bacterial colonization. The exact timing of intestinal col
onization is not yet certain. From a retrospective analysis of 24 neon
ates with intestinal perforation and a prospective study of 30 ill neo
nates aged less than 10 days who recieved intestinal-tract operations,
we found that the incidence of bacterial growth from small- and large
-bowel specimens was significantly lower within 48 h after birth and t
he intestinal tract was almost completely sterile within 24 h after de
livery. Most of the bacteria were aerobic gram-negative bacilli, and t
he most common species was Escherichia coli. Although our results may
not represent conditions in the normal neonate, knowledge of bowel col
onization in such patients will be helpful for further management.