Evaluation of probiotic treatment in a neonatal animal model

The clinical use of probiotic agents such as enteral Lactobacillus to enhance intestinal defense against potential luminal pathogens has been tested in vivo; however, an understanding of the mechanisms responsible for the observed protection is lacking. The purpose of this study was to evaluate the effects of Lactobacillus on bacterial translocation (BT) in a neonatal animal model. Newborn New Zealand white rabbit pups were enterally fed a 10% Formulae solution inoculated with or without a 10⁸ suspension of ampicillin-resistant Escherichia coli K1 (E. coli K1A) and/or Lactobacillus casei GG (Lacto GG). Pups received either no bacteria (n = 10), Lacto GG (n = 8), E. coli K1A (n = 26), or a combination of Lacto GG and E. coli K1A (n = 33). On day 3, representative tissue specimens from the mesenteric lymph nodes (MLN), spleen (SPL), and liver (LIV) were aseptically harvested in addition to a small-bowel (SB) sample that was rinsed to remove luminal contents. The specimens were then cultured in organism-specific media. Statistical analysis was by one-way ANOVA with P values less than 0.05 considered significant. Neonatal rabbits receiving Lacto GG-supplemented formula exhibited a 25% decrease (P < 0.05) in small-bowel colonization by E. coli K1A. In addition, Lacto GG decreased the frequency of extraintestinal BT by 46% (P < 0.05), 61% (P < 0.05), and 23%, respectively, in the MLN, SPL, and LIV. We have shown that enterally-administered Lacto GG decreases the frequency of E. coli K1A translocation in a neonatal rabbit model. These results may have significant implications for the treatment of BT and sepsis in the human neonate and provide a model for further studies.