Search

Introduction: We have previously shown that rabbit breast milk, or breast milk-derived secretory IgA (sIgA), but not IgG nor lactoferrin, protects neonatal rabbits from bacterial translocation (BT). However, it is not known whether this protection is species-specific. Cross-species effectiveness of sIgA could make it an important adjunct in the treatment or prevention of necrotizing enterocolitis (NEC) or gut-origin sepsis. We hypothesized that human breast milk (HBM) may protect neonatal rabbits from BT by agglutinating the indigenous intestinal microbial flora, a process known as immune exclusion. Methods: Newborn rabbits were randomized to receive a nutritionally complete artificial formula, or an equal volume of HBM. Quantitative cultures of the blood, mesenteric lymph nodes, liver, spleen, and cecum were obtained on day 6 for BT. sIgA, IgG, and lactoferrin were isolated from HBM via ion-exchange chromatography and tested for their ability to agglutinate translocating bacteria in vitro. Results: Neonates fed HBM had a significantly lower incidence of BT than those fed formula (4/9 v. 8/8; p =0.029, Fischer's Exact test). There was no significant difference in the cecal flora, or in the species of transiocating organisms between the two groups. E coli, Enterobacter, Enterococcus, and Lactobacillus were the most common translocating organisms. HBM, sIgA, and IgG agglutinated each species of bacteria to varying degrees. Lactoferrin and formula had no effect. Conclusion: Our data show that HBM protects neonatal rabbits from BT without altering the composition or quantity of cecal flora. The mechanism likely involves IgA-mediated immune exclusion, since it is 5 times more abundant in human breast milk than IgG and is more resistant to proteolytic degradation in the stomach than IgG. This finding may have far-reaching implications for the prevention of NEC or of intestinal barrier failure, especially in formula-fed premature infants., EP Nadler MD, X Zhou PhD, K Wong, P Boyle, Y Chen MD, PhD, HR Ford MD, FAAP; Children's Hospital of Pittsburgh, Pittsburgh, PA [...]