INFLUENCE OF PRENATAL CORTICOSTEROIDS ON BACTERIAL-COLONIZATION IN THE NEWBORN RAT

The interactions between bacteria and the host's intestinal barrier ap pear to be important regulators of bacterial colonization. In this stu dy we investigated the effect of prenatal corticosteroids, known to ac celerate the intestinal maturation of newborn rats, on bacterial colon ization in the rat pup. Pregnant rats were treated with either cortiso ne acetate or normal saline on days 18-21 of gestation and were allowe d to deliver spontaneously. The pups, after normal delivery, were sacr ificed at different times during the first 10 days of life. The entire small intestine was removed, and each lumen was flushed to exclude no nadherent, transient organisms and homogenized. Tenfold dilutions were plated on horse-blood agar (total bacteria) and MacConkey's medium (g ram-negatives). Quantitation and bacterial typification was determined after 24 h of incubation at 37-degrees-C. Total bacteria and gram-neg atives found in association with the mucosa were significantly lower i n pups prenatally treated with steroids. These changes were not relate d to any changes in motility or intraluminal digestion. This suggests that the developmental condition of the host's intestinal barrier may be an important regulator of the bacterial microenvironment of the new born small intestinal mucosa.