The Intestinal Microbiota: Prebiotics, Probiotics, Symbiotics Flashcards
What is the difference between microbiota and microbiome?
microbiota: all the living microrganisms that inhabit the host
microbiome: the mutual interaction of these organisms with the host cells
What important role does the microbiota play in host health?
- stimulate the immune system and development of gut structure
- aid in defense against invading pathogens
- provide nutritional benefits to the host
what are the different methods of characterizing the microbiota?
bacterial culture
molecular technique: RNA/DNA, PCR, analysis of amplicons (denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE), and terminal restriction fragment length polymorphism (T-RFLP)), quantification (qPCR, FISH)
metagenomics (gene content)
transcriptomics (gene expression)
What are the pros and cons to performing a bacterial culture for microbiota analysis?
What type of bacteria predominates in the GI tract?
What specific bacterial groups predominate?
anaerobes
Bacteroides, Clostridium, Lactobacillus, Bifidobacterium spp., and Enterobacteriaceae.
What prevents the retrograde movement of bacteria from the colon into the SI normally?
ileocolic valve along with normal intestinal motility
The bacterial population in the GI tract is very stable. What are the mechanisms that control the bacterila populations?
(1) gastric acid
(2) the antimicrobial effect of bile
(3) intestinal motility
(4) intestinal mucus
(5) local immune responses
What type of archaea are most abundant in the GI tract?
What type of fungi is most abundant?
Most viral sequences represent what type of virus?
Methanobacteria or methanogens (metabolize Hydrogen end product of bacterial fermentaiton to methane better than hydrogen sulfite)
yeast and molds
bacteriophage
For PCR amplification of bacteria, what gene is used?
16s rRNA
What information does the analysis of amplicons (DGGE, TGGE, T-RFLP) provide?
phylogenetic
What is the concepto of colonization resistance?
The microbiota also protects the host from invading pathogens→This occurs through competition for oxygen, nutrients, and mucosal adhesion sites as well as creation of a physiologically restrictive barrier for nonresident bacteria.
What allows for communication between the microbiota and host immune system?
What benefits does this communication system provide?
TLR (toll-like receptors)
Substances that inhibitbacteiral growth
bacteriocins
What is the main product of fermentation that serves as an energy source for the bacteria and promotes epithelial cell growth in the colon?
volatile fatty acids (7% of ME)
What are the three main ways GI disease can result in relationship to the microbiota and immune system dysfunction?
- pathogen colonization
- overgrowth of commensal organisms
- altered communication
What types of bacteria increase with IBD?
Decrease with IBD?
Increase with boxer histiocytic ulcerative colitis?
Proteobacteria in the duodenum
beneficial Clostridium clusters.
adherent and invasive E. coli (respond to treatment with fluoroquinolones)
What pathogens that colonize in GI tract often cause GI disease?
salmonella
campylobacter
C. difficile
What conditions are associated with overgrowth of commensals?
dysbiosis
ARD (abx responsive diarrhea)- SI bacterial overgrowth (SIBO)
EPI→SIBO
SX→altered motility
Types of altered communication of microbiota and immune system that results in GI disease?
shift toward gram negative organisms→decreases colonization resistance
TLR→alterations to T-cells
histiocytic ulcerative colitis in boxers (intracellular E. Coli)
What two conditions are abx most commonly used to rebalance the microbiota?
- intstinal dysbiosis (ARD/SIBO)
- IBD
What are prebiotics?
What two benefits do they provide?
Examples?
nondigestible dietary carbohydrates
Benefits:
- stimulate the growth and metabolism of endogenous enteric protective bacteria (Lactobacillus and Bifidobacterium)
- increase SCFA
Examples: lactosucrose, fructooligosaccharides (FOS), psyllium, and bran
What are probiotics?
living microrganisms that impart a health benefit beyond basic nutrition
What are the proposed benefits of probiotics?
What are the most commonly studied microrganisms?
- improved epithelial barrier function
- modulation of mucosal immune system
- alteration of the microbiota, specifically inhibiting colonization by pathogenic bacteria
Lactobacilli, Bifidobacteria, and Enterococci have been the most commonly studied.
What information should the manufacturer provide for a probiotic?
- the number of live, microbial colony-forming units per unit weight
- genus,
- species, and (preferably) strain
of each organism
