Septic Stability? Gut Microbiota in Young Adult MICE Maintains Overall Stability After Sepsis Compared to Old Adult MICE.

Mankowski, Robert T; Thomas, Ryan M; Darden, Dijoia B; Gharaibeh, Raad Z; Hawkins, Russell B; Cox, Michael C; Apple, Camille; Nacionales, Dina C; Ungaro, Ricardo F; Dirain, Marvin L; Moore, Fredrick A; Leeuwenburgh, Christiaan; Brakenridge, Scott C; Clanton, Thomas L; Laitano, Orlando; Moldawer, Lyle L; Mohr, Alicia M; Efron, Philip A

BACKGROUND Older adults have worse outcomes after sepsis than young adults. Additionally, alterations of the gut microbiota have been demonstrated to contribute to sepsis-related mortality. We sought to determine if there were alterations in the gut microbiota with a novel sepsis model in old adult mice, which enter a state of persistent inflammation, immunosuppression and catabolism (PICS), as compared to young adult mice, which recover with the sepsis model. METHODS Mixed sex old (∼20 mo) and young (∼4 mo) C57Bl/6J mice underwent cecal ligation and puncture with daily chronic stress (CLP+DCS) and were compared to naive age-matched controls. Mice were sacrificed at CLP+DCS day 7 and feces collected for bacterial DNA isolation. The V3-V4 hypervariable region was amplified, 16S rRNA gene sequencing performed, and cohorts compared. α-Diversity was assessed using Chao1 and Shannon indices using rarefied counts, and β-diversity was assessed using Bray-Curtis dissimilarity. RESULTS Naïve old adult mice had significantly different α and β-diversity compared to naïve adult young adult mice. After CLP+DCS, there was a significant shift in the α and β-diversity (FDR = 0.03 for both) of old adult mice (naïve vs. CLP+DCS). However, no significant shift was displayed in the microbiota of young mice that underwent CLP+DCS in regards to α-diversity (FDR = 0.052) and β-diversity (FDR = 0.12), demonstrating a greater overall stability of their microbiota at 7 days despite the septic insult. The taxonomic changes in old mice undergoing CLP+DCS were dominated by decreased abundance of the order Clostridiales and genera Oscillospira. CONCLUSION Young adult mice maintain an overall microbiome stability 7 days after CLP+DCS after compared to old adult mice. The lack of microbiome stability could contribute to PICS and worse long-term outcomes in older adult sepsis survivors. Further studies are warranted to elucidate mechanistic pathways and potential therapeutics.