title: Giardia duodenalis induces pathogenic dysbiosis of human intestinal microbiota biofilms.
abstract: Giardia duodenalis is a prevalent cause of acute diarrheal disease worldwide. However, recent outbreaks in Italy and Norway have revealed a link between giardiasis and the subsequent development of chronic post-infectious irritable bowel syndrome. While the mechanisms underlying the causation of post-infectious irritable bowel syndrome remain obscure, recent findings suggest that alterations in gut microbiota communities are linked to the pathophysiology of irritable bowel syndrome. In the present study, we use a laboratory biofilm system to culture and enrich mucosal microbiota from human intestinal biopsies. Subsequently, we show that co-culture with Giardia induces disturbances in biofilm species composition and biofilm structure resulting in microbiota communities that are intrinsically dysbiotic - even after the clearance of Giardia. These microbiota abnormalities were mediated in part by secretory-excretory Giardia cysteine proteases. Using in vitro cell culture and germ-free murine infection models, we show that Giardia-induced disruptions of microbiota promote bacterial invasion, resulting in epithelial apoptosis, tight junctional disruption, and bacterial translocation across an intestinal epithelial barrier. Additionally, these dysbiotic microbiota communities resulted in increased activation of the Toll-like receptor 4 signalling pathway, and overproduction of the pro-inflammatory cytokine IL-1beta in humanized germ-free mice. Previous studies that have sought explanations and risk factors for the development of post-infectious irritable bowel syndrome have focused on features of enteropathogens and attributes of the infected host. We propose that polymicrobial interactions involving Giardia and gut microbiota may cause persistent dysbiosis, offering a new interpretation of the reasons why those afflicted with giardiasis are predisposed to gastrointestinal disorders post-infection.
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Beatty
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Sarah V
authors.initials: SV
authors.lastname: Akierman
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada; Department of Physiology & Pharmacology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Motta
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Stacy
authors.initials: S
authors.lastname: Muise
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Workentine
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Joe J
authors.initials: JJ
authors.lastname: Harrison
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Amol
authors.initials: A
authors.lastname: Bhargava
authors.affiliation: Department of Medicine, Division of Gastroenterology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Beck
authors.affiliation: Department of Medicine, Division of Gastroenterology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Rioux
authors.affiliation: Department of Medicine, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Gordon Webb
authors.initials: GW
authors.lastname: McKnight
authors.affiliation: Department of Physiology & Pharmacology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: John L
authors.initials: JL
authors.lastname: Wallace
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 4N1, Canada; Department of Physiology & Pharmacology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada. Electronic address: aburet@ucalgary.ca.
authors.forename: Andre G
authors.initials: AG
authors.lastname: Buret
mesh_terms: D000818:Animals; D017209:Apoptosis; D018441:Biofilms / Q000254:growth & development*; D001706:Biopsy; D018938:Caco-2 Cells; D003106:Colon / Q000382:microbiology / Q000473:pathology; D057056:Cysteine Proteases / Q000378:metabolism; D005243:Feces / Q000382:microbiology / Q000469:parasitology; D000069196:Gastrointestinal Microbiome / Q000502:physiology*; D005856:Germ-Free Life; D016829:Giardia lamblia / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D005873:Giardiasis / Q000150:complications* / Q000469:parasitology; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology; D043183:Irritable Bowel Syndrome / Q000209:etiology*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D011817:Rabbits; D051381:Rats; D013559:Symbiosis
chemical_list: D057056:Cysteine Proteases
keywords: Biofilm; Gastrointestinal microbiome; Giardia duodenalis; Post-infectious irritable bowel syndrome