(474) Microbial Responses to Enteral Nutrition With Prebiotic scFOS in Critically Ill Trauma Patients

Introduction: Microbial dysbiosis in the intensive care unit (ICU) is common, and expansion of potential pathogens such as Enterobacteriaceae may contribute to mortality. Prebiotic enteral nutrition formulations with short-chain fructooligosaccharides (scFOS-EN) are hypothesized to limit pathogen expansion and support beneficial microbes. Though these formulations are widely available, the impact of scFOS-EN on microbial responses in critical illness are unknown. We conducted a pilot randomized control trial (RCT) in critically ill trauma patients to evaluate effects of scFOS-EN versus a fiber-free formula (NF-EN) on microbial responses and interactions.

Methods: In this blinded RCT at a level 1 trauma center, mechanically-ventilated ICU patients with severe trauma (excluding GI injury) were randomized to scFOS-EN or NF-EN for 10 days. 16S rRNA sequencing was used to profile microbiota from serially collected stool and oral samples. We used linear mixed models to compare microbial responses over time between scFOS-EN and NF-EN and network analyses to explore interactions between gut microbes.

Results: A total of 57 stool and 88 oral samples were included from 10 scFOS-EN and 7 NF-EN patients. All patients received antibiotics and derangements in gut microbiota were present at time of formula initiation. While oral responses were similar, formula type impacted abundances of numerous gut microbes. Compared to NF-EN, scFOS-EN was associated with an accelerated loss of Bifidobacterium (-0.6% relative abundance/day, p=.026), and Firmicutes (3.5%/day, p<.001), and expansion of numerous Bacteroidaceae. Only scFOS-EN patients showed an increase in Enterobacteriaceae (0.3%/day, p=.003). Network analyses revealed that interactions between Enterobacteriaceae and Bacteroidaceae may underly changes in microbiota to scFOS-EN.

Conclusions: scFOS-EN in ICU-associated dysbiosis may deplete beneficial bacteria like Bifidobacterium and Firmicutes while promoting resilient Bacteroidaceae, potentially providing a context-dependent advantage to pathobiont Enterobacteriaceae. Our findings underscore the importance of investigating microbial interactions in critically ill patients to inform microbiota-targeted therapies.