Antibacterial and anti-inflammatory effects of Lactobacillus reuteri in its biofilm state contribute to its beneficial effects in a rat model of experimental necrotizing enterocolitis

•Reuterin and histamine contribute to the efficacy of biofilm Lr against NEC.•Infectious and inflammatory components contribute to the etiology of NEC.•Administration of Lr as a biofilm could be a potential therapeutic for clinical NEC. Necrotizing enterocolitis (NEC) remains a significant surgical emergency in neonates. We have demonstrated the efficacy of Lactobacillus reuteri (Lr) in protecting against experimental NEC when administered as a biofilm by incubation with maltose loaded dextranomer microspheres. Lr possesses antimicrobial and anti-inflammatory properties. We developed mutant strains of Lr to examine the importance of its antimicrobial and anti-inflammatory properties in protecting the intestines from NEC. Premature rat pups were exposed to hypoxia/hypothermia/hypertonic feeds to induce NEC. To examine the importance of antimicrobial reuterin and anti-inflammatory histamine, pups received either native or mutant forms of Lr, in either its planktonic or biofilm states, prior to induction of NEC. Intestinal histology was examined upon sacrifice. Compared to no treatment, administration of a single dose of Lr in its biofilm state significantly decreased the incidence of NEC (67% vs. 18%, p