Bacterial translocation in neonatal rats: the relation between intestinal flora, translocated bacteria, and influence of milk.

BACKGROUND

A high incidence of bacterial translocation in neonates results not only from immaturity of host-defense functions, but also from the dominant colonization of aerobic bacteria in the intestine. Bacterial colonization develops differently among breast-fed, formula-fed, premature, and full-term infants. The purpose of this study was to examine the incidence of bacterial translocation and to identify the translocated bacterial species, relating these findings to the intestinal microflora and to the type of feeding in neonatal rats.

METHODS

Animals were divided into three groups: breast-fed normal pups (MR group), formula-fed pups fed via an intragastric cannula implanted esophageally (AR group), and breast-fed pups after the removal of the cannula (Sham group). Artificial rearing was achieved using a machine feeding system. Culture and identification of the bacteria in the intestine, mesenteric lymph nodes, liver, portal blood, and lungs were made using a simplified version of Mitsuoka's method.

RESULTS

At 14 days of age, the dominant bacteria in the feces of the MR and Sham Groups were Enterobacteriaceae, Lactobacillus, and Enterococcus, but Enterobacteriaceae and Clostridium were significantly more common in the AR group than in the MR group. The dominant bacteria in the mesenteric lymph nodes were Enterobacteriaceae, Lactobacillus, and Staphylococcus. The extent of systemic bacterial translocation decreased earlier in the Sham group than in the AR group.

CONCLUSIONS

The frequency with which species of bacteria were cultured from mesenteric lymph nodes and other peripheral sites did not mirror the composition of the intestinal flora. Among the translocated bacteria, Staphylococcus may be especially hard to recognize and difficult for the host-defense systems to destroy. Breast-feeding inhibited systemic bacterial translocation in the suckling period of the rat.