Persistence and dynamics of fluorescent in the healthy inflamed gut.

The gastrointestinal tract is the main ecological niche in which strains may provide health benefits in mammals. There is currently a need to characterize host-microbe interactions in space and time by tracking these bacteria . We combined noninvasive whole-body imaging with fluorescence confocal microscopy imaging to monitor the impact of intestinal inflammation on the persistence of orally administered NCIMB8826 in healthy and inflamed mouse colons. We developed fluorescent strains and demonstrated that mCherry is the best system for imaging and fluorescence confocal microscopy of these bacteria. We also used whole-body imaging to show that this anti-inflammatory, orally administered strain persists for longer and at higher counts in the inflamed colon than in the healthy colon. We confirmed these results by the confocal imaging of colons from mice with experimental colitis for 3 days after induction. Moreover, extended orthogonal view projections enabled us to localize individual in sites that differed for healthy inflamed guts. In healthy colons, orally administered bacteria were localized in the lumen (in close contact with commensal bacteria) and sometimes in the crypts (albeit very rarely in contact with intestinal cells). The bacteria were observed within and outside the mucus layer. In contrast, bacteria in the inflamed colon were mostly located in the lumen and (in less inflamed areas) within the mucus layer. In more intensely inflamed areas (i.e., where the colon had undergone structural damage), the were in direct contact with damaged epithelial cells. Taken as a whole, our results show that fluorescently labeled can be used to study the persistence of these bacteria in inflamed guts using both noninvasive whole-body imaging and fluorescence confocal microscopy.