Intestinal mucosal layers are colonized by a complex microbiota that provides beneficial effects under normal physiological conditions, but is capable of contributing to chronic inflammatory disease such as inflammatory bowel disease (IBD) in susceptible individuals. Studies have shown that the enteric microbiota may drive the development of the gut immune system and can induce immune homeostasis as well as contribute to the development of IBD although the precise etiology is still unknown. Therefore, intestinal microbes seem to play a key role in the disease pathogenesis. Especially, dysbiosis, which is a shift in the composition of enteric microbiota to a nonphysiologic composition, is associated with one or more defects in mucosal immune functions, including microbe recognition, barrier function, intercellular communication, and anti-microbial effector mechanisms. This review focuses on the impact of enteric microbiota on the development and perpetuation of IBD. In addition, interactions with enteric bacteria and mucosal cells, including intestinal epithelial cells, dendritic cells, and T cells, to induce immune responses at mucosal surfaces have been discussed in the point of IBD pathogenesis. Further extension of the knowledge of enteric microbiota may lead to insights on the pathogenesis and new therapeutic strategies for IBD.
Bacterial Physiological Phenomena ; Host-Pathogen Interactions ; Humans ; Inflammatory Bowel Diseases/*microbiology/pathology ; Intestinal Mucosa/immunology/microbiology ; Intestines/microbiology/pathology ; T-Lymphocytes/immunology/metabolism

Advances in sequencing technology and the development of metagenomics have opened up new ways to investigate the microorganisms inhabiting the human gut. The intestinal microbiota confer protection against pathogens, contribute to the maturation of the immune system, and regulate host metabolism. The composition of gut microbiota in early life is influenced by mode of birth, diet, and antibiotics. Decreased biodiversity and alterations in the composition of the intestinal microbiota have been observed in many diseases including obesity, neonatal necrotizing enterocolitis, inflammatory bowel disease, and recurrent Clostridium difficile infection. Therapeutic options for the diseases linked to imbalance in the microbiota include modifying the gut microbiota through diet, probiotics, and fecal transplants.
Animals ; Anti-Bacterial Agents/therapeutic use ; Clostridium difficile/isolation & purification/pathogenicity ; Enterocolitis, Pseudomembranous/drug therapy/microbiology/pathology ; Fatty Liver/etiology/microbiology ; Humans ; Inflammatory Bowel Diseases/etiology/microbiology ; Intestines/*microbiology ; *Microbiota ; Obesity/etiology/microbiology

No abstract available.
Adult ; Aged ; Biopsy ; Colon/*microbiology/pathology ; Fusobacterium/genetics/*isolation & purification ; Humans ; Inflammatory Bowel Diseases/microbiology/*pathology ; Male ; Middle Aged ; Polymerase Chain Reaction ; RNA, Ribosomal, 16S/chemistry/genetics/metabolism ; Republic of Korea ; Sequence Analysis, DNA ; Young Adult