Gut microbiota biofilm disruptions by Giardia: Pathology in human enterocytes and germ‐free mice

Giardia duodenalis may cause post‐infectious Irritable Bowel Syndrome (PI‐IBS). Mechanisms underlying PI‐IBS are unknown, but disruptions in the intestinal microbiota of IBS patients are documented. The intestinal microflora exists as biofilms, and we hypothesized that disruptions in these communities may lead to PIIBS. Aim To study effects of Giardia on the species, and pathogenic profile of microflora biofilms. Methods Microbiota from human colonic mucosal biospies were cultivated as biofilms, and assessed in CaCo2 monolayers and germ‐free (GF) mice. Results Giardia alters species profiles in microflora biofilms, and promotes planktonic growth via exopolysaccharide breakdown. Monolayers exposed to Giardia ‐treated biofilms showed altered occludin and TLR‐4 expression, and apoptosis. GF mice humanized with Giardia ‐treated biofilms show mucosal granulomas and increased mast cell tryptase. Conclusion Giardia disrupts human microbiota biofilms, which disturb epithelial integrity and TLR‐4 expression, and cause intestinal pathophysiology in GF mice. The data illustrate novel pathways employed by pathogens that may lead to PI‐IBS. Supported by NSERC.