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20 Cards in this Set

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probiotics

live microorganisms which when administered in adequate amounts confer a health benefit on the host

prebiotics

dietary substances that nurture a selected group of microorganisms living in the gut


-favour growth of beneficial bacteria over harmful bacteria

eg of prebiotics

fermentable carbs:


-oligofructose, inulin, galacto-oligosaccharides, lactulose


-found in cookies, cereals, chocolate, dairy products




eg: fermentation of oligofructose in colon


--> increase # of bifidobacteria


--> increase calcium abs


--> increase fecal weight


--> shortening of GI transit time

probiotic uses

-prevent and treat conditions caused by pathogenic bacteria (tx and prevention of AAD, acute infectious diarrhea)


-eradication of H pylori


-boost immune response


-prevent URTIs


-improve IBD and IBS


-improve lactose intolerance


-decrease cholesterol


-assist in weight loss

mechanism of probiotic/host interaction

Theory 1: restore balance to intestinal flora


Theory 2: anti-microbial effects


Theory 3: stimulate immune fxn

Theory 1: restore balance to intestinal flora

-counteract disturbances by recolonizing the intestine and crowding out 'bad' bacteria


-compete for adhesion helping to enhance epithelial barrier (help w mucous production)

theory 2: antimicrobial effects

-produce substances (lactic/acetic acid, peroxides, or bacteriocins (toxins)) to block colonization of pathogens

theory 3: stimulate immune fxn

-enhance Ab production and natural killer cell activity; alter cytokine release


-improve phagocytic activity




*only in healthy individuals; not people w immune system hypersensitivity

properties of an ideal probiotic

-high adherence to intestinal wall


-stable against gastric acid, bile, oxygen & enzymes


-nonpathogenic


-able to co-aggregate as part of the natural gut flora


-resistant to the effects of an abx


-evidence for a health benefit

main microorganisms used in probiotic formulation

Lactobacillus


Bifidobacteria


Saccharomyces

Lactobacillus

G+ rods, anaerobes


-able to survive gastric conditions better than bifidobacteria


-do not require enteric coating


-can latch onto intestinal wall for _> 1w


-lactic acid producing


-used to ferment milk to make yogurt


-aka Acidophilus

Bifidobacteria

G+, anaerobes


-mostly colonize in the colon


-appear to be the most important organism in intestine for providing a microbial barrier to infection


-also a lactic acid bacteria


-predominant intestinal flora of breast-fed infants

saccharomyces boulardii

a nonpathogenic yeast


-mostly colonize in the colon


-believed to be a strain of Saccharomyces cerevisiae (baker's yeast)

Abx-associated diarrhea (AAD)

occurrence: 1-44%


-caused by disruption of gut microbiota caused by abx therapy


-episodes range from mild (stopping when abx stop) to serious (bowel perforation, death)




increased risk w:


-age, co-morbidity, broad spectrum abx, length of tx

efficacy in AAD

-evidence supports use of S. boulardii and L. rhamnosus GG


-insufficient evidence to rate: Bifidobacteria




more effective at higher doses?


_> 50 billion cfu/d




take for same duration as abx


-space doses by 2h


-continue 1-2w after d/c abx (?)

efficacy in CDAD

evidence positive


-specific strain, length of tx, safety in immunocompromised not known




L. rhamnosus, LGG (Culturelle) most often used


some evidence for S. boulardii




doses used: at least 10 billion organisms/d

efficacy in IBS

fairly positive evidence for treating overall sx and abdominal pain in IBS


-supporting evidence for B. infantis 35624

efficacy in prevention of acute URTI

better than placebo at reducing # episodes and duration (0.4 of a day) -CS??


-quality of evidence is very LOW




most studied was Lactobacillus (different spp. & strains)


-most given w milk-based food


-doses used: 10^9 or 10^10 CFU/d

yogurt vs NHP?

available in fermented dairy foods


-stability is an issue (should be refridgerated)


-some yogurts contain encapsulated powdered bacteria


-short shelf life




pharmaceutically based delivery systems are more reliable

adverse effects

-very well tolerated


common SE:


-transient: bloating, diarrhea, abdominal discomfort




may down-regulate immune fxn in immunocompromised pts -best to avoid