Flashcards in Microbiome App Deck (25)
What does microbiome mean?
The collective genome of symbionts
What is normal biota?
Microbial pathogens found on and in us
What is the first line of defense?
Why do we use 16S rDNA?
To identify previously unknown bacteria
To answer these questions:
How stable an individual's microbiota are? Do all humans have a core microbiome? What effects genetic diversity of the microbiome?
What are the most common mechanisms of bacterial interference?
Harmless bacteria displacing pathogenic bacteria; Fecal microbiota transplant used to restore missing bacteroidetes and firmicutes
What can happen is resident microbiota are disturbed?
Transient microbiota may take over and cause disease
What oral bacteria may cause endocarditis after tooth extraction?
Streptococci of the viridans group (alpha-hemolytic strep other than S. pneumoniae)
Early dental plaque:
Gram positive colonizers such as Streptococcus sanguis; specific ionic and hydrophobic interactions as well as lectin-like surface structures adhere to the pellicle
Late dental plaque:
Gram negative anaerobes; make high molecular weight polyglycans
What is the role of sucrose in dental caries?
Sucrose is the substrate S. mutans uses and produces acid along with extracellular polyglycans and levans by transferase enzymes
What is the most significant bacteria in dental caries?
What is responsible for damage to the periodontium?
Bio-film induced chronic inflammatory disease (host response is responsible)
What are the strategies to prevent dental caries and periodontitis?
Removal of calcified deposits
Limited sucrose intake
Good nutrition with adequate protein intake
Reduction of acid production by decreasing carb intake
What is the quantity of bacteria in the stomach vs the colon like?
Stomach: few due to low pH
Colon: gradually increasing due to alkalinity
What is the type of bacteria in the stomach and colon respectively?
Stomach: H. pylori
What are the major functions of intestinal microbiota in defense?
Defense: displaces potential pathogens indirectly by competing for nutrients and receptors or antimicrobial factors
Induce secretions of IgA and develop intestinal humoral immunity and modulate T cell response and cytokine profiles
Major functions of intestinal microbiota in metabolism:
Contribute AA to host
Produce short-chain FA to control intestinal epithelial cell differentiation
Synthesize vitamin K, biotin, folate and ion absorption
Aid in fermentation and nondigestible dietary residues
Fat gut deposit leading to obesity
Mechanisms by which methanogens increase ATP production in bacteria:
Reduce small organic compounds into methane in the presence of H2; removal of excess H2 prevents the inhibition of bacterial NADH dehydrogenase
Rationale of doing a FMT in C. difficile infection?
Displace harmful bacteria
Restore colonic microbiota to natural state by replacing bacteroidetes and firmicutes
How can oral administration of insoluble antibiotics affect gut flora during and after treatment?
Result in self-limiting diarrhea or life-threatening pseudomembranous colitis
Intentional suppression of fecal flora is done preoperatively
What insoluble antibiotics are given for aerobic bacteria?
Neomyocin + erythromycin
What insoluble antibiotics are given for anaerobic bacteria?
What species cause peritoneal abscesses in cases of colonic perforation?
Bacteroides fragilis (penicillin resistant)
What role do microbiota and host immunity play in inflammatory bowel diseases?
Associated with loss of immune tolerance to bacterial antigens
Leads to intense inflammation caused by an exuberant immune response