Intestinal microbial diversity and perioperative complications

Abstract

Background and aims: Enteral nutrient deprivation via parenteral nutrition (PN) in a mouse model leads to a local mucosal inflammatory response. This proinflammatory response leads to a loss of epithelial barrier function and atrophy of the intestine. Although the underlying mechanisms are unknown, a potential contributing factor is the impact PN has on the intestinal microbiome. We recently identified a shift in the intestinal microbial community in mice given PN; however, it is unknown whether such changes occur in humans. We hypothesized that similar microbial changes occur in humans during periods of enteral nutrient deprivation.

Methods: A series of small bowel specimens were obtained from pediatric and adult patients undergoing small intestinal resection. Mucosally associated bacteria were harvested and analyzed using 454 pyrosequencing techniques. Statistical analysis of microbial diversity and differences in microbial characteristics were assessed between enterally fed and enterally deprived portions of the intestine. Occurrence of postoperative infectious and anastomotic complications was also examined.

Results: Pyrosequencing demonstrated a wide variability in microbial diversity within all groups. Principal coordinate analysis demonstrated only a partial stratification of microbial communities between fed and enterally deprived groups. Interestingly, a tight correlation was identified in patients who had a low level of enteric microbial diversity and those who developed postoperative enteric-derived infections or intestinal anastomotic disruption.

Conclusions: Loss of enteral nutrients and systemic antibiotic therapy in humans is associated with a significant loss of microbial biodiversity within the small bowel mucosa. These changes were associated with a number of enteric-derived intestinal infections and intestinal anastomotic disruptions.

Keywords: intestine; microbiota; microflora; parenteral nutrition.

Figures

Figure 1

Phylum level analysis after Ribosomal Database Project (RDP) classification of pyrosequenced small bowel mucosa-associated bacteria samples. Groups of patients are broken down by degree of enteral nutrition, as well as by separating the two neonatal samples. Mucous fistula denotes bowel completely unexposed to nutrients and partial feeding meant intestine where

Figure 2

Unweighted Unifrac principal coordinates analysis of control and TPN small bowel samples. Axis-1 (X) and axis-2 (Y) account for 11.9% and 8.6% of overall differences, respectively.

Figure 3

Inverse Simpson index and enteral nutrition. All patients outside of the newborn period with a sample that scored less than 10, signifying a less diverse microbiota, were complicated with an infectious or anastomotic complication(*).