Why Does SIBO Keep Coming Back After Treatment? — Why the loss of epithelial hypoxia drives the recurrence

The healthy colonic environment is hospitable to obligate anaerobes because the colonocytes consume the oxygen at the surface. Faecalibacterium prausnitzii , Roseburia intestinalis , the Lachnospiraceae and Ruminococcaceae more broadly, the taxa most consistently associated with healthy gut function, are obligate anaerobes that cannot survive at meaningful oxygen concentrations. The healthy community is built by the host. The host's oxygen consumption creates the niche the community lives in. When colonocyte oxidative metabolism falters, oxygen consumption falls. Oxygen leaks into the lumen. The obligate anaerobes lose their competitive advantage. Facultative anaerobes, particularly Enterobacteriaceae like E. coli and Klebsiella , and in some patients the sulfate-reducing taxa, expand into the new aerobic-tolerant environment. This is the mechanism of dysbiosis viewed correctly. It is not a primary microbial disease. It is the readout of a host substrate that has lost the capacity to define its own niche. The microbial composition changes because the conditions that maintained the previous composition no longer exist. Antimicrobial treatment in this state reduces the displaced community temporarily. The Enterobacteriaceae or sulfate-reducers are knocked down. But the colonocyte substrate failure that allowed them to expand has not been addressed. The luminal oxygen remains elev