Intestinal Microbiota And Butyrate Depletion Drive Gut-Derived Infections In Necrotizing Pancreatitis

Author(s):
Fons van den Berg; Demi van Dalen; Hjalmar van Santvoort; Sanjiv Hyoju; Marc Besselink; Olga Zaborina; Marja Boermeester; John Alverdy

Background:

Secondary infections in necrotizing pancreatitis are predominantly caused by inhabitants of the gastrointestinal tract.

Hypothesis:

We hypothesize that disruption of the intestinal mucosa microbiota – more specifically a shift from obligate anaerobes to an increase of low abundance aerobic pathogens and depletion of butyrate-producers – is driving infectious complications in acute pancreatitis.

Methods:

Comparative fecal microbiota analysis was done in 35 Dutch patients with mild or severe acute pancreatitis. Necrotizing pancreatitis in the mouse model was induced by retrograde infusion of taurocholic acid into the
pancreatic duct. 6 week old mice were fed a high fat/low fiber Polyunsaturated Fatty Acids (PUFA) diet for 4 weeks prior to the procedure to alter the intestinal microbiota. Mice were postoperatively treated with
placebo or i.p. butyrate injections and monitored for survival during 72 hours. Blood and organs were collected for bacteriology, immune analysis by cytokine assay, and compositional by 16S rRNA sequencing and functional by Biolog Phenotype Microarray analyses of the microbiota. Luminal concentrations of short-chain fatty acids (butyrate, propionate, acetate) in the cecum were measured by gas chromatography-mass spectrometry.

Results:

The analysis of human samples demonstrated a domination of potential pathogens in fecal samples in patients with severe pancreatitis. Furthermore, the relative abundance of butyrate-producing bacterial genera was lower in patients with severe acute pancreatitis, as compared to patients with mild acute pancreatitis. In the mouse model, PUFA fed mice showed a sharp decrease in survival (18%, n=11 versus 100% in chow-fed mice, n=14, p<0.001) and an increase of gram-negative bacteria (predominant Escherichia coli) during necrotizing pancreatitis. Cecal microbiota analysis showed a decrease in alpha-diversity and a bloom of mucosa-adherent E.coli in the moribund mice. Functional analysis revealed an enhanced aerobic metabolic activity of cecal bacterial communities in moribund mice, and a depletion of luminal butyrate concentrations. Reiterative experiments demonstrated that 88% of the mice were rescued with intraperitoneal butyrate injection (n=7, p<0.001). Intestinal abundance of E.coli, bacterial dissemination, serum endotoxin, and IL-6 levels were reduced with butyrate treatment.

Conclusions:

This data indicates that disruption of the gut microbiota promotes bacterial dissemination and contributes to severe infections in necrotizing pancreatitis. Butyrate treatment is potentially effective in reducing bacterial dissemination and mortality in necrotizing pancreatitis and may be used as prophylactic therapy. However, the underlying mechanisms are largely unknown and remain under investigation.