## 7 The Oral Microbiota and Gut Microbiota Axis
### Beneficial Gut Commensal Organisms  
Many studies examining probiotic supplementation for the treatment of IBD have shown improvement in patient symptoms [116], however, more research examining the diverse relationships of multiple system environments, such as the oral cavity and digestive tract, must be investigated [117; 118]. In a paramount study by [PERSON] et al., the commensal organism _Faecalibacterium prausnitzii (F. prausnitzii)_ was delivered orally to 2,4,6-trinitrobenzenesulfonic acid (TNBS)-treated colitis mouse models and controls. Results showed _F. prausnitzii_ and its supernatant were able to successfully improve the fecal microbiota of colitis-induced mice. In patients with CD, as well as in vitro with Caco-2-cells, _F. prausnitzii_ attenuated NF-kB activation and pro-inflammatory IL-8 secretion resulting in anti-inflammatory effects along with improved shifts in the microbiota composition [119]. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Phylum** & **Genus** & **Species** & **Morphology** & **Reference** \\ \hline Proteobacteria & _Klebsiella_ & _Klebsiella pneumoniae_ & Nonmotile, encapsulated, rod-shaped bacilli, facultative anaerobic & [111] \\ Proteobacteria & _Enterobacter_ & _Enterobacter_ spp. & Rod-shaped bacilli, non-spore-forming, motile, facultative anaerobic & [49] \\ Proteobacteria & _Neisseria_ & _Neisseria_ spp. & Lipooligosaccharide (LOS), strict aerobe & [114] \\ Bacteroidetes & _Prerotella_ & _Prerotella nigrescens_ & Nonmotile, rod-shaped bacilli, anaerobic & [115] \\ Fusobacteria & _Fusobacterium_ & _Fusobacterium_ spp. & Non-spore forming, rod-shaped bacilli, potent & [115] \\  & & & LPS, anaerobic & \\ Bacteroidetes & _Porphyomonas_ & _Porphyomonas gingivalis_ & Nonmotile, Gram-negative, anaerobic, rod-shaped & [108] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Bacteria species found in both periodontitis infection and inflammatory bowel disease (IBD). Figure 3: Immune dysregulation mediated by the gut microbiota dysbiosis in an inflammatory bowel disease intestinal epithelium after ectopic colonization by oral pathologists. Follicle associated epithelium (FAE) shown by a Peyer’s patch and germinal center including naïve B and T cells maturing into memory B cells and plasma B cells. Ectopic colonization of pathologists at the intestinal epithelium shows depleted mucus layers and inadequate intestinal barrier protection by tight junctions as well as reduced diversity of gut microbiota and abundance of pathogenic organisms. Pictured is also infiltration of immune cells as well as polarization of MI macrophage cells. Abbreviations: MLN, mesenteric lymph node; FAE, follicle associated epithelium; DC, dendritic cells; MI, M1 macrophages. While it is difficult to pinpoint the range of IBD symptom-ameliorating bacteria, there are several phyla commonly found in healthy participants, such as _F. prausnitzii_[119] and _Roseburia_ spp. [120], which may be lacking in patients with IBD. Several studies indicate the positive effects of specific probiotic bacteria for humans, such as strains belonging to the genera _Lactobacillus_ and _Bifidobacterium_[121]. _Lactobacillus casei_ (_L. casei_) and _Lactobacillus rhamnus_ (_L. rhamnus_) are among the most studied strains of probiotics for their wide-range of notable health benefits [122]. In a study administering fermented milk products containing _Bifidobacterium lactis_ in murine models with colitis, researchers found a decrease in inflammation due to metabolic shifts stemming from a change in gut microbial profiles. This evidence suggests the shift to a more robust commensal bacterial gut environment may protect the lining of the gut and create a non-permissive environment for opportunistic strains [123]. Along with gut barrier protection, metabolites of intestinal bacterial species may be associated with overall human health [124; 125]. For example, the well-studied probiotic strain _L.