P1.174: Mucous Fistula Refeeding and the Intestinal Microbiome Following Surgical Necrotizing Enterocolitis and Spontaneous Intestinal Perforation

Background: The neonatal microbiome is critical for gut development. Neonates with necrotizing enterocolitis (NEC) or spontaneous intestinal perforation (SIP) may require intestinal resection with creation of an ostomy. In our institution, these patients may undergo mucous fistula refeeding (MFR), the introduction of the proximal ostomy output into the distal mucous fistula to optimize intestinal function. However, there is little data on how the microbiome is affected by intestinal resection and MFR.

This study aimed to understand the baseline characteristics of the intestinal microbiome and the effects of MFR on the microbiome in neonates who underwent intestinal resection for NEC or SIP.

Methods: This was a prospective study conducted in a level 4 NICU, from February to September 2024. Initially, 27 neonates diagnosed with NEC or SIP met screening criteria; 12 were excluded due to death prior to consent, or no parental consent. Of the remaining patients, 3 died and 2 did not complete the study, leaving 10 patients in the final study.

Stool samples were collected from all participants’ ostomy sites after resection and prior to MFR. In the 8 patients who underwent MFR, rectal samples were collected every 1-2 weeks after starting MFR and before intestinal reconnection. In the 2 patients who did not undergo MFR, 6 additional ostomy samples were collected. Rectal stool samples were collected from all patients every 1-2 weeks after intestinal reconnection. There were 62 stool samples from MFR patients and 15 samples from non-MFR patients. Samples were stored at -80C until 16S rRNA gene sequencing was performed. Permutational multivariate analysis of variance was completed to adjust for gestational age, birth weight, maternal race, weight on admission and antibiotic doses.

Results: Among MFR patients, there was a difference in the beta-diversity from the initial ostomy samples compared to stool samples collected after MFR (p-value: 0.0002), with higher abundance of Firmicutes after initiation of MFR. There was also a difference in beta-diversity between initial ostomy samples and stool samples collected after reconnection (p-value: 0.0006), with higher abundance of Firmicutes in initial ostomy samples. Finally, a difference in beta-diversity between rectal stool samples collected during MFR compared to rectal stool samples collected after intestinal reconnection was noted (p-value: 0.0228); however, there was not enough power to determine what these differences were.

Conclusion: Our findings suggest that MFR may promote a healthy microbiome as we identified a higher abundance of Firmicutes during MFR. We will also compare the microbiome of patients with and without MFR; however, due to low number of non-MFR patients, we may not have enough power to identify differences. Thus, a larger study is needed to clarify whether MFR promotes normalization of the intestinal microbiome in neonates.