The microenvironment influences the pattern of bacterial translocation in formula-fed neonates.

The authors previously demonstrated that neonatal rabbits fed conventional formula have a significantly greater incident of bacterial translocation than do neonatal rabbits fed breast milk. They hypothesized that exogenous bacteria in the formula and/or the microenvironment of the neonatal rabbit may contribute to the higher incidence of bacterial translocation. In the present study, the authors examined the incidence of bacterial translocation in neonatal rabbits fed pasteurized formula, unsterile formula, or breast milk while being housed in a clean or unsterile environment. The rabbits were divided into five groups. Groups I and II were fed pasteurized formula; groups III and IV were fed unsterile formula. In addition, groups I and III were housed in a clean environment, and groups II and IV were kept in an unsterile environment. The neonates in group V were fed breast milk and were kept in an unsterile environment. On the seventh day, the animals were killed, and the mesenteric lymph nodes, liver, and spleen were cultured for the presence of bacteria. Bacterial translocation occurred in 100% of group IV neonates. A clean environment (groups I and III) eliminated gram-negative bacterial translocation. A reduction (50%) in the overall incidence of bacterial translocation was obtained by pasteurizing the formula (group I v group III). Group II had significantly less gram-negative bacterial translocation than did group IV. None of the neonates in group V had translocation. The data show that a clean environment abrogates gram-negative bacterial translocation. Pasteurizing the formula significantly reduces the incidence of gram-negative bacterial translocation, and further reduces overall bacterial translocation in a clean environment. The authors hypothesize that control of the microenvironment can significantly influence the pattern of bacterial translocation in formula-fed neonates, and thus potentially reduce the incidence of gut-origin sepsis. Factors present in breast milk inhibit bacterial translocation, regardless of the microenvironment.