Intestinal colonization leading to fecal urobilinoid excretion may play a role in the pathogenesis of neonatal jaundice

Background: Neonatal hyperbilirubinemia remains of concern because of the p otential danger for the central nervous system. Because urobilinogen is a n ontoxic derivative of bilirubin, the current study was conducted to examine the fecal excretion of urobilinoids and bilirubin in healthy newborns and infants, as well as their intestinal bacteria capable of reducing bilirubin , to assess a possible relation to serum bilirubin levels during the first weeks of life. Methods: Bilirubin pigments, urobilinoids, and porphyrins were measured in stools of infants during the first week (group A, n = 60) and between the s econd week and the first 6 months of life (group B, it = 64). Microbiologic analysis of stools was performed in selected cases and bilirubin-convertin g activity of isolated bacteria was determined in vitro. Results: Urobilinoids were detectable in stools of 57% of the neonates at d ay 5, but not before. However, fecal urobilinoid production on that day was only a fraction of that observed in adults (0.07 vs. 0.7-3.6 mg/kg per day ), whereas at week 6 it increased significantly to an average of 0.9 md/kg per day. Microbiologic analysis of neonatal stools revealed two novel bacte rial strains of Clostridium perfringens and Clostridium difficile capable o f reducing bilirubin to urobilinoids. Conclusions: Urobilinoids can be detected in stools of 57% of newborns at d ay 5 after delivery. However, the urobilinoid production during the first w eek of life is quantitatively insufficient to contribute significantly to t he removal of bilirubin. Enhancement of the microbial conversion of bilirub in could decrease the intestinal concentration of bilirubin and may decreas e the degree or enhance the removal of neonatal hyperbilirubinemia. (C) 200 0 Lippincott Williams & Wilkins, Inc.