Time course of spontaneous bacterial translocation from gastrointestinal tract and its relationship to intestinal microflora in conventionally rearedinfant rats

Whereas the developed gut mucosal barrier prevents luminal bacteria from in vading the host, bacterial translocation appears to be facilitated in the n eonate. The aim of this study was to determine the extent to which bacteria spontaneously translocate from the gut to extraintestinal organs during th e neonatal period and to relate translocation to the evolving intestinal fl ora in the rat. Newborn Sprague-Dawley rats suckled nd libitum and ate regu lar chow after weaning. A total of 167 rats were killed either immediately or at 1, 9, 14, 21, 26, or 42 days after delivery. Mesenteric lymph nodes ( MLN), liver, heart blood, and the terminal ileal loop were harvested under sterile conditions and analyzed for aerobic and facultatively anaerobic bac teria by standard microbiologic procedures. Bacterial translocation to the MLN and liver began soon after birth and peaked during the second week. On day 14, translocation to any organ was present in 85% of rats. All cultures from the liver were sterile after day 26. By contrast, the fall in translo cation to the MLN was incomplete, as 50% of pups still had positive MLN on day 42. Blood cultures were positive in three of the 167 rats. The intensit y of translocation as determined by the number of organs infected significa ntly increased with the number of gram-negative enterics and gram-positive cocci in the gut and was negatively correlated with the percentage of lacto bacilli from the total measured intestinal flora (P < 0.0001). In conclusio n, bacterial translocation from the gut is a physiological and age-dependen t phenomenon in the neonatal rat. Translocation appears to be facilitated w hen intestinal concentrations of gram-negative enterics and gram-positive c occi are high and when the concentration of lactobacilli is low.