In writing this review, we relied on original articles and reviews that were published in scientific journals and are searchable in database libraries (OVID, PubMed, Medline Plus Databases), and on our current readings on the topic. Due to space limitations, the number of studies quoted has been restricted. We chose articles for citation on the basis of the relevance of its contents without any bias toward author or journal.
ReviewGut flora in health and disease
Section snippets
Composition of the flora
Colonisation of the gastrointestinal tract of newborn infants starts immediately after birth and occurs within a the birth canal versus caesarean section) and the type of diet (breast versus formula feeding) might affect the colonisation pattern.7, 8, 9, 10 Other environmental factors also have a major role since differences exist between infants born in developed countries and those born in developing countries, and between infants from different hospital wards.11, 12, 13 Pioneer bacteria can
Main functions of microflora
Use of animals bred under germ-free conditions has provided important information about the effect of the microbial community of the gut on host physiology and pathology.24 Evidence obtained through such studies25 suggests that microflora have important and specific metabolic, trophic, and protective functions (panel).
Translocation of bacteria
The passage of viable bacteria from the gastrointestinal tract through the epithelial mucosa is called bacterial translocation.70 Translocation of endotoxins from viable or dead bacteria in very small amounts probably constitutes a physiologically important boost to the reticuloendothelial system, especially to the Kupffer cells in the liver. However, dysfunction of the gut mucosal barrier can result in translocation of many viable microorganisms, usually belonging to gram-negative aerobic
Colon cancer
The molecular genetic mechanisms of colorectal cancer are well established, but environmental factors such as diet might also have a major role in development of sporadic colon cancer. Dietary fat and high consumption of red meat, especially processed meat, are associated with high risk of colon cancer.76 By contrast, a high intake of fruits and vegetables, whole grain cereals, fish, and calcium has been associated with reduced risk.76, 77 Dietary factors and genetic factors interact in part
Inflammatory bowel diseases
Resident bacterial flora have been suggested to be an essential factor in driving the inflammatory process in human inflammatory bowel diseases.86 In patients with Crohn's disease, intestinal T lymphocytes are hyperreactive against bacterial antigens, and Pirzer and colleagues87 suggested that local tolerance mechanisms are abrogated in such patients. In addition, patients with Crohn's disease or ulcerative colitis have increased intestinal mucosal secretion of IgG type antibodies against a
Probiotics and prebiotics
Bacteria can be used to improve human health. A bacterium that provides specific health benefits when consumed as a food component or supplement would be called a probiotic. A consensus definition of the term was issued a few years ago and states that oral probiotics are living microorganisms that upon ingestion in specific numbers, exert health benefits beyond those of inherent basic nutrition.102 According to this definition, probiotics do not necessarily colonise the human intestine. The
Recommendations
A better understanding of our relations with the microbial world should help in prevention of diseases such as atopy, colon cancer, and inflammatory bowel diseases.
Search strategy and selection criteria
Conflict of interest statement
F Guarner and J-R Malagelada are
References (132)
- et al.
Intestinal flora in health and disease
Gastroenterology
(1984) - et al.
Development of anaerobic fecal flora in healthy newborn infants
J Pediatr
(1977) - et al.
Fermentation in the human large intestine and the available substrates
Am J Clin Nutr
(1987) - et al.
Ileal recovery of starch from whole diets containing resistant starch measured in vitro and fermentation of ileal effluent
Am J Clin Nutr
(1995) - et al.
Phytate breakdown and apparent absorption of phosphorus, calcium and magnesium in germfree and conventionalized rats
Nutr Res
(1996) - et al.
Carbohydrate fermentation decreases hepatic glucose output in healthy subjects
Metabolism
(1993) - et al.
Rapidly available glucose in foods: an in vitro measurement that reflects the glycemic response
Am J Clin Nutr
(1999) - et al.
Chronic consumption of short-chain fructooligosaccharides does not affect basal hepatic glucose production or insulin resistance in type 2 diabetics
J Nutr
(2000) - et al.
Mediation of the trophic effects of short-chain fatty acids on the rat jejunum and colon
Gastroenterology
(1994) - et al.
Immunobiology and immuno-pathology of human gut mucosa: humoral immunity and intraepithelial lymphocytes
Gastroenterology
(1989)
The absence of gut flora, the doses of antigen ingested and aging affect the long-term peripheral tolerance induced by ovalbumin feeding in mice
Res Immunol
The role of intestinal microflora on the prevention of Salmonella colonization in gnotobiotic chickens
Poultry Sci
Intestinal bacteial overgrowth and bacterial translocation in cirrhotic rats with ascites
J Hepatol
Specific species of intestinal bacteria influence the induction of aberrant crypt foci by 1,2-dimethylhydrazine in rats
Cancer Lett
Inflammatory bowel disease: Immunodiagnostics, immunotherapeutics, and ecotherapeutics
Gastroenterology
Reactivity of infiltrating T lymphocytes with microbial antigens in Crohn's disease
Lancet
Mucosal flora in inflammatory bowel disease
Gastroenterology
Association between insertion mutation in NOD2 gene and Crohn's disease in German and British populations
Lancet
Induction of wasting disease in SCID mice by the transfer of normal CD4+/CD45RBhi T cells and the regulation of this autoreactivity by CD4+/CD45RBlo T cells
Res Immunol
Stimulation of transforming growth factor- 1 by enteric bacteria in the pathogenesis of rat intestinal fibrosis
Gastroenterology
Early lesions of recurrent Crohn's disease caused by infusion of intestinal contents in excluded ileum
Gastroenterology
Microbial flora of the gastrointestinal tract
Ecological control of the gastrointestinal tract: the role of probiotic flora
Gut
Intra-abdominal infections
The microbial contribution to human faecal mass
J Med Microbiol
Functional food science and gastrointestinal physiology and function
Br J Nutr
Development and differences of intestinal flora in the neonatal period in breast-fed and bottle-fed infants
Pediatrics
Analysis of intestinal flora development in breast-fed and formula-fed infants by using molecular identification and detection methods
J Pediatr Gastroenterol Nutr
Fecal microflora in healthy infants born by different methods of delivery: permanent changes in intestinal flora after cesarean delivery
J Pediatr Gastroenterol Nutr
Effect of feeding on infants' faecal flora
Arch Dis Child
The composition of the faecal microflora in breastfed and bottle fed infants from birth to eight weeks
Acta Paediatr Scand
Intestinal colonization of enterobacteriaceae in Pakistani and Swedish hospital delivered children
Acta Pediatr Scand
Molecular analysis of commensal host-microbial relationships in the intestine
Science
Installation, équilibre et rôle de la flore microbienne du nouveau-né
Annales Pédiatriques
Intestinal floras of populations that have a high risk of colon cancer
Appl Environ Microbiol
Human colonic biota studied by ribosomal DNA sequence analysis
Appl Environ Microbiol
Direct rDNA community analysis reveals a myriad of novel bacterial lineages within the human gut
ApplEnviron Microbiol
Molecular assessment of intestinal microflora
AmJClin Nutr
Analysis of fecal populations of bifidobacteria and lactobacilli and investigation of the immunological responses of their human hosts to the predominant strains
Appl Environ Microbiol
Quantification of bacterial groups within human fecal flora by oligonucleotide probe hybridization
Appl Environ Microbiol
Variations of bacterial populations in human feces measured by fluorescent in situ hybridization with group-specific 16S rRNA-targeted oligonucleotide probes
Appl Environ Microbiol
Comparative study of bacterial groups within the human cecal and fecal microbiota
Appl Environ Microbiol
Creating and maintaining the gastrointestinal ecosystem: what we know and need to know from gnotobiology
Microbiol Mol Biol Rev
Colonic microflora: nutrition and health: summary and conclusions of an International Life Sciences Institute (ILSI) (Europe)] workshop held in Barcelona, Spain
Nutr Rev
Short chain fatty acids in human large intestine, portal, hepatic and venous blood
Gut
Digestion and physiological properties of resistant starch in the human large bowel
Br J Nutr
Protein degradation by human intestinal bacteria
J Gen Microbiol
Enumeration of human colonic bacteria producing phenolic and indolic compounds: effects of pH, carbohydrate availability and retention time on dissimilatory aromatic amino acid metabolism
J Appl Bacteriol
Intraluminal pH of the human gastrointestinal tract
Dan Med Bull
Comparison of fermentation reactions in different regions of the human colon
ApplBacteriol
Cited by (2657)
The role of the gut microbiome in gastrointestinal cancers
2024, Cellular SignallingThe Effect of Nutrient Deprivation on Early Life Small Intestinal Mucosal Microbiome and Host Proteome
2024, Journal of Nutrition