539 - Colonizing intestine with a multi-strain probiotic promotes gastrointestinal motility and decreases inflammation in an animal model of necrotizing enterocolitis

Poster Number: 539
Publication Number: 539.2076

Background: Administration of probiotics to preterm infants can decrease the incidence of necrotizing enterocolitis (NEC) through largely unknown mechanisms. Previous studies show that gastrointestinal dysmotility develops in NEC before the onset of systemic disease.

Objective: We hypothesize that colonization of the premature intestine with a multi-strain probiotic can prevent NEC in mice by promoting gastrointestinal motility.

Design/Methods: All experiments were approved by the Animal Care and Use Committee of our university (Protocol MO23M234). Newborn C57BL/6 mice were fed a multi-strain probiotic from postnatal day 3 to 11, consisting of Bifidobacterium infantis, Bifidobacterium lactis and Streptococcus thermophilus. Colonization was tested by 16s qRT-PCR using strain-specific primers on bacterial DNA isolated from stool. From postnatal day 7, mice were exposed to an experimental model of NEC by formula feeding with NEC bacteria and 0.5% DSS and intermittent hypoxia (5% O2, 10min exposure, twice daily) for 4 days. To evaluate gastrointestinal motility, mice were fed FITC-dextran (70Kda, 10mg/ml, 50ul/mouse), 30-min prior to sacrifice. The small intestine was divided into 1cm sections and FITC fluorescence was measured for each section. The small intestinal transit time was derived from the position of the geometric (Geom) center of FITC-dextran. Proinflammatory mediators were evaluated by measuring a gene expression profile through total RNA isolation from ileum and colon followed by qRT-PCR.

Results: Probiotic colonization was confirmed in probiotic-fed mice and not in controls. The induction of NEC was associated with markedly reduced intestinal motility that was improved in probiotic colonized mice (Geom Center, Probiotics/NEC 4.4 vs. non-probiotics/NEC 2.9, **p < 0.01). Probiotic administration improved clinical features of NEC development (pneumatosis, discoloration of the bowel) and mortality rate (Probiotics/NEC 14% vs. non-probiotics/NEC 50%). Pro-inflammatory mediators TLR4, TNF and IL1B were reduced, mainly in the colon, in probiotic fed mice compared to non-probiotic fed mice (TLR4, Probiotics/NEC 41.1 vs. non-probiotics/NEC 62.9, **p < 0.01; TNF 5.9 vs.16.4, ***p < 0.001; IL1B, 1.5 vs. 3.4, **p < 0.01).

Conclusion(s): The need for better understanding of the working mechanism of probiotics has been highlighted by recent FDA investigations. Our findings suggest that probiotic administration may prevent NEC in part by restoring gastrointestinal motility and decreasing the inflammatory response. Further investigations into the exact mechanism through which motility is restored are currently ongoing.