DETERMINANT OF BACTERIAL TRANSLOCATION IN THE NEWBORN - SMALL-BOWEL VERSUS LARGE-BOWEL COLONIZATION

This study investigated the relationship between bacterial translocati on (BT) and small and large bowel bacterial colonization in the neonat al rabbit. The authors have previously shown that spontaneous BT occur s in rabbits during the first week of life, but is less frequent befor e the third day of life. The authors have also shown that bacterial co lonization of the small bowel is delayed until 3 to 5 days of age, and is preceded by colonization of the large bowel. Therefore, the author s hypothesized that BT is dependent on small bowel, not large bowel, c olonization. New Zealand White rabbit pups (n = 255) were divided into four groups, formula-fed (FF), formula-fed plus antibiotic (FFAB), br east-fed (BF) and unfed controls (UC). Animals from each group were ki lled on day 1 to 4 of life. Small bowel (SE) and large bowel (LB) spec imens, mesenteric lymph nodes (MLN), spleen (SPL), and liver (LIV) wer e obtained from each rabbit, incubated for 24 hours in thioglycolate b roth, and plated on both MacConkey and Colistin Naladixic Acid media i n an aerobic environment. After 24 hours, growth on either plate was r ecorded. Bacterial colonization was significantly greater in FF versus UC, BF, and FFAB rabbit groups. In addition, large bowel colonization was significantly increased compared with small bowel colonization in all feeding groups (P < .05). Bacterial translocation to MLN, SPL, an d LIV ranged from 10% to 27% in all groups. Gram-negative bacteria pre dominated over gram-positive bacteria in translocation to the various tissues sampled. The ratio of gram-negative to gram-positive bacteria was greater in the UC, FF, and FFAB groups compared with that of the B F rabbit group. Bacterial translocation to all tissues in all feeding groups was significantly correlated with small bowel bacterial coloniz ation (P < .05). The incidence of bacterial translocation to MLN in sm all bowel positive rabbits was significantly decreased in the BF group compared with the FF and FFAB groups at 3 days of age. The authors co nclude the following: (1) Bacterial translocation almost always requir es small bowel colonization. Colonization of the large bowel alone rar ely leads to translocation if the small bower is sterile. (2) Enteral antibiotics had no effect on bacterial translocation. (3) These findin gs may explain why necrotizing enterocolitis and neonatal sepsis do no t occur during the first 3 to 5 days of life when small bowel bacteria l colonization is absent. Copyright (C) 1995 by W.B. Saunders Company