Quantitative and morphologic analysis of bacterial translocation in neonates
L. L. Go, H. R. Ford, S. C. Watkins, P. J. Healey, C. T. Albanese, A. Donhalek, R. L. Simmons and M. I. Rowe
Department of Surgery, University of Pittsburgh (Pa) School of Medicine.
OBJECTIVE: To elucidate the mechanisms of bacterial translocation in
animals fed a conventional formula by correlating transmucosal bacterial
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 days, and
transmucosal passage of bacteria was measured in vitro using the Ussing
chamber. The mucosal membranes were examined by light, transmission
electron, and confocal laser scanning microscopy. RESULTS: Bacterial
passage was rarely seen in the breast milk-fed animals in contrast to the
formula-fed animals. Unlike the normal-appearing membranes from breast
milk-fed animals, the epithelial cells of formula-fed animals were
vacuolated but healthy, with normal polarization and microvillus border by
confocal laser scanning microscopy. Villi of formula-fed animals were less
densely packed than those of the breast milk-fed animals. Bacterial
adhesion, internalization, and transmucosal passage were seen only in
membranes from formula-fed animals. Transmission electron microscopy
demonstrated bacteria incorporating into the epithelial surface through an
active phagocytic process, with rearrangement of the actin cytoskeleton.
Once internalized, these bacteria were seen within the cytoplasmic vacuoles
and subsequently in the submucosa. No bacteria passed between epithelial
cells. CONCLUSION: Morphological changes in the intestinal mucosa of
formula-fed newborn rabbits may increase permeability to bacteria.
