OC-020 The Murine Gastric Microbiome is Influenced Both by Helicobacter Felis Infection and Somatic Deletion of NF-Kappab Family Members
Authors: S L Burgess, J Caamaño, D M Pritchard, M Burkitt
Journal: Gut (2013)

<h3>Introduction</h3> The development of gastric atrophy in C57BL/6 mice infected with <i>Helicobacter felis</i> is differentially regulated by signalling involving NF-κB1 and NF-κB2. After infection, more severe atrophy developed in <i>Nfkb1</i><i><sup>-/-</sup></i> mice than wild-type (WT), whilst <i>Nfkb2</i><i><sup>-/-</sup></i> mice were protected from atrophic gastritis. Previous studies have also shown that the development of <i>H. pylori</i> induced gastric pathology was delayed in INS-Gas mice maintained in germ free, compared to conventional animal house conditions. Consequently we hypothesised that the different phenotypes observed in <i>H. felis</i> infected mice lacking specific NF-κB proteins may be influenced by altered gastric microbiomes. We have therefore quantified the abundance of specific bacterial phyla in <i>Nfkb1</i><i><sup>-/-</sup></i>, <i>Nfkb2</i><i><sup>-/-</sup></i> and C57BL/6 mice with and without <i>H. felis</i> infection. <h3>Methods</h3> Groups of 3 C57BL/6, <i>Nfkb1</i><i>-/-</i> and <i>Nfkb2</i><i>-/-</i> mice aged 6 weeks were infected with <i>H. felis</i> by gavage. Animals were euthanased at 12 weeks and gastric antral DNA was extracted. Total bacterial load and relative abundance of α<i>-Proteobacteria</i>, γ<i>-Proteobacteria</i>, <i>Bacteriodetes</i>, <i>Firmicutes</i> and <i>Actinobacteria</i> were determined by qPCR of 16S rDNA. <i>H. felis</i> colonisation was quantified by qPCR for <i>Flaa,</i> samples were normalised to murine<i> Gapdh</i>. <h3>Results</h3> Untreated WT mice had 3.4 and 2.6 fold greater universal bacterial transcripts than <i>Nfkb1</i><i>-/-</i> and <i>Nfkb2</i><i>-/-</i> mice respectively. <i>Actinobacteria</i> abundance was 6.0 fold greater in untreated <i>Nfkb1</i><i>-/-</i> mice <i>cf</i> WT and 7.0 times greater in <i>Nfkb2</i><i>-/-</i> mice. α<i>-Proteobacteria</i> were 9.0 times more abundant in untreated <i>Nfkb1</i><i>-/-</i> mice <i>cf</i> WT. <i>H. felis</i> infection of WT mice resulted in 5.6 and 16.7 fold increases in α<i>-Proteobacteria</i> and γ<i>-Proteobacteria</i> respectively<i> cf</i> uninfected mice. γ<i>-Proteobacteria</i> were more abundant in all infected groups, but significantly more so in <i>Nfkb2</i><i>-/-</i> mice than others. This correlated with a 30 fold higher abundance of <i>H. felis</i> (Phylum: γ<i>-Proteobacteria</i>) in infected <i>Nfkb2</i><i>-/-</i> compared to WT mice. Infected <i>Nfkb2</i><i>-/-</i> mice also had a 3.3 fold greater abundance of <i>Actinobacteria</i><i>cf</i> infected WT mice. No statistically significant differences were observed in the abundance of <i>Firmicutes</i> or <i>Bacteroidetes</i>. <h3>Conclusion</h3> Constitution of the murine gastric antral microbiome is influenced both by <i>Helicobacter felis</i> infection and somatic deletion of NF-κB family members. Since deletion of NF-κB1 and NF-κB2 have been reported to alter susceptibility to <i>H. felis</i> induced gastric atrophy, these data support the hypothesis that specific differences in microbiota may be responsible for, or reflect this altered susceptibility. Further studies are needed to determine whether specific organisms influence the development of gastric pathology either individually or within complex communities. <h3>Disclosure of Interest</h3> None Declared