QUANTITATIVE AND MORPHOLOGIC ANALYSIS OF BACTERIAL TRANSLOCATION IN NEONATES

Objective: To elucidate the mechanisms of bacterial translocation in a nimals fed a conventional formula by correlating transmucosal bacteria l passage in vitro with the structural characteristics of the neonatal intestinal mucosa. Design: Newborn rabbits were randomized to receive a conventional formula or breast milk. Bacterial translocation to the mesenteric lymph nodes, liver, and spleen was quantitated after 7 day s, and transmucosal passage of bacteria was measured in vitro using th e Ussing chamber. The mucosal membranes were examined by light, transm ission electron, and confocal laser scanning microscopy. Results: Bact erial passage was rarely seen in the breast milk-fed animals in contra st to the formula-fed animals. Unlike the normal-appearing membranes f rom breast milk-fed animals, the epithelial cells of formula-fed anima ls were vacuolated but healthy, with normal polarization and microvill us border by confocal laser scanning microscopy. Villi of formula-fed animals were less densely packed than those of the breast milk-fed ani mals. Bacterial adhesion, internalization, and transmucosal passage we re seen only in membranes from formula-fed animals. Transmission elect ron microscopy demonstrated bacteria incorporating into the epithelial surface through an active phagocytic process, with rearrangement of t he actin cytoskeleton. Once internalized, these bacteria were seen wit hin the cytoplasmic vacuoles and subsequently in the submucosa. No bac teria passed between epithelial cells. Conclusion: Morphological chang es in the intestinal mucosa of formula-fed newborn rabbits may increas e permeability to bacteria.