A Novel IBD‐Associated Mouse Pathobiont E. coli Causes Disease and Prevents Recovery from Colitis
Authors: Shawki Ali , Spalinger Marianne R. , Santos Alina N. , Canale Vinicius , Sayoc-Becerra Anica , Mitchell Jonathan , Macbeth John , Ruegger Paul M. , Borneman James , Hsiao Ansel , McCole Declan F. 
Published: April 2020

IntroductionExpansion of intestinal pathobionts, such as adherent‐invasive E. coli (AIEC), are strongly implicated in the pathogenesis of Inflammatory Bowel Disease (IBD) as AIEC increases pro‐inflammatory cytokine production and alters tight junction protein regulation, suggesting a potential mechanism of pathogen‐induced barrier dysfunction and inflammation. In mice lacking the IBD risk gene, protein tyrosine phosphatase non‐receptor Type 2 (PTPN2), we previously showed increased abundance of a novel mouse AIEC (mAIEC) which had sequence match identity of a 250bp segment to the human IBD‐associated AIEC, LF82. We functionally validated the ability of mAIEC to adhere to and invade intestinal epithelial cells in vitro. The aim of this study was to determine if mAIEC can cause disease in vivo and whether it requires other bacteria to support its pathogenicity in mice.Methods(1) Germ‐free ~12‐week old C57Bl/6 male and female mice; or (2) wild‐type 10‐week old confirmed segmented filamentous bacteria (SFB)‐free C57Bl/6 female mice (JAX labs, Stock# 000664) ± 3% dextran‐sodium sulfate (DSS) for 7 days housed in a specific pathogen‐free (SPF) vivarium; were orally gavaged with PBS or gavaged with 109 CFU of either pure mAIEC or K12 at exponential‐phase growth. Germ‐free mice received fecal microbiome transplant (FMT) by oral gavage of fresh caecal content from a Ptpn2‐KO (KO‐FMT) mouse at day 22 post‐mAIEC colonization. Disease activity index (DAI) was assessed by measuring weight loss, physical activity, general appearance, and stool consistency.ResultsmAIEC infected SFB‐free mice had a significant decrease in body weight development (P = 0.002, n = 5) but no apparent increase in DAI compared with the control E. coli K12 or PBS conditions. Infection of germ‐free mice with mAIEC did not alter body weight development compared with K12 infected mice. However, recolonization with KO‐FMT post‐mAIEC infection caused sustained weight loss in male but not female mice compared with K12 mice (P = 0.02, n = 3). To identify the effects of mAIEC infection on inflammation, SFB‐free mice were orally gavaged with mAIEC on days 0–3 of DSS administration. mAIEC+DSS treated mice showed a more severe drop in body weight development, increased disease severity (P < 0.001, n = 4–5), and a worse barrier defect associated with translocation of bacteria to the spleen and liver (P ≤ 0.002, n = 3–5) compared with DSS+PBS, DSS+K12 or non‐DSS treated PBS, mAIEC or K12 alone control groups. When administered to mice with established DSS colitis, mAIEC prevented recovery from DSS‐induced colitis compared with K12 and PBS conditions (P ≤ 0.009, n = 5).ConclusionsWe describe for the first time a novel IBD‐associated mouse AIEC that can cause or worsen disease in a host, but requires other bacteria to support its pathogenicity. This study generates new insights into environment‐microbiome interactions in IBD.Support or Funding InformationCrohn’s and Colitis Foundation Senior Research Award (D.F.M.); NIH‐2R01‐DK091281 (D.F.M.); American Gastroenterological Association IBD Research Award (D.F.M.). UCR Office of Research & Economic Development Pilot Award (D.F.M. & J.B.).