The clinical use of probiotic agents such as enteral Lactobacillus to enhan
ce intestinal defense against potential luminal pathogens has been tested i
n vivo; however, an understanding of the mechanisms responsible for the obs
erved protection is lacking. The purpose of this study was to evaluate the
effects of Lactobacillus on bacterial translocation (BT) in a neonatal anim
al model. Newborn New Zealand white rabbit pups were enterally fed a 10% Fo
rmulae solution inoculated with or without a 10(8) suspension of ampicillin
-resistant Escherichia coli K1 (E. coli K1A) and/or Lactobacillus casei GG
(Lacto GC). 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 ill addition
to a small-bowel (SB) sample that was rinsed to remove luminal contents. T
he specimens were then cultured in organism-specific media. Statistical ana
lysis was by one-way ANOVA with P values less than 0.05 considered signific
ant. Neonatal rabbits receiving Lacto GG-supplemented formula exhibited a 2
5% decrease(P < 0.05) in small-bowel colonization by E, coli K1A. In additi
on, 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 CC decreases the frequency of E. c
oli K1A translocation in a neonatal rabbit model. These results may have si
gnificant implications for the treatment of BT and sepsis in the human neon
ate and provide a model for further studies.