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Microbes and You > Probiotics L3 > Flashcards

Probiotics L3 Flashcards

1
Q

what is a probiotic

A

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

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2
Q

what is the beneficial bacteria effect in normal gut flora

A

health-promoting bacteria

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3
Q

what are examples of beneficial bacterial in the gut flora

A

lactobacilli and bifidobacteria

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4
Q

is the normal gut flora harmful

A

Potentially harmful or pathogenic bacteria

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5
Q

example of harmful gut flora

A

e.g. clostridia

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6
Q

what can harmful gut flora cause

A

May cause a person to a number of clinical diseases: including bowel cancer and inflammatory bowel diseases

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7
Q

what do probiotics aim to improve

A

aim to improve numbers of beneficial bacteria, reduce the numbers/effects of the detrimental species

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8
Q

what are some probiotic properties

A
  • Beneficial effect on host
  • Nonpathogenic and nontoxic
  • Contain large number of viable cells
  • Capable of surviving and metabolising in gut
  • Remain viable during storage and use
  • Good sensory properties
  • Isolated from same species as intended host, e.g. from a human if for human consumption
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9
Q

how do probiotics survive through the GI tract

A

Resistance to bile, hydrochloric acid and pancreatic juice

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10
Q

what are the beneficial effects on the host caused by probiotics

A
  • Colonisation of gastrointestinal tract in humans
  • Adherence to epithelial cells (colonisation ability and immune system cross-talk)
  • Antimicrobial activity – outcompete detrimental bacteria naturally in intestine
  • Anti-carcinogenic activity (reduction of carcinogen levels)
  • Immune modulation or stimulation in human trials
  • Reduction of intestinal permeability in human trials, stopping other organism passing across gut membrane into blood stream then to rest body
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11
Q

how are probiotics designed for stress tolerance

A
  • Salivary enzymes
  • Gastric enzymes
  • Body temperature, survive stomach acids
  • Low pH
  • Gastric juice
  • Bile salts
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12
Q

how do probiotics have adhesion ability

A
  • Autoggregation assays, bacteria stick together
  • Degree of hydrophobicity, how water replent they are
  • Adhesion to mammalia epithelial cells
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13
Q

what is the anti-pathogenic activity caused by probioitcs

A
  • Antimicrobial metabolites production, do they make anything that kill other bacteria
  • Can they outcompete pathogenic bacteria
  • Co-aggregation with pathogens, can they survive and join with pathogens present
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14
Q

what are the safety assessments for probiotics

A
  • Taxonomy identification – know what exact organism it is
  • Absence virulence
  • Enterotoxins (toxin produced in/affecting intestines) production
  • Haemolytic activity – destruction of red blood cells
  • Transferable antibiotic resistance genes, genes that will lead to antibiotic resistance
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15
Q

what are the host associated functional properties that probiotics have

A
  • Anticancer
  • Anti-cholesterol
  • Antidepressant
  • Anti-anxiety
  • Anti-obesity
  • Anti-diabetic
  • Immunostimulant, do they stimulate immune system
  • Secretion of functional molecules
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16
Q

what are the mechanisms of probiotic activities

A
  1. Antimicrobial activities
  2. Improved environment for beneficial bacteria to grow
  3. Production of beneficial end products
  4. Reduce of harmful end products
  5. stimulation of the immune system as a defence against pathogens
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17
Q

what end products do probiotics reduce

A

reduced levels of carcinogens by inactivating enzymes e.g. nitrate reductase that can result in the production of carcinogens

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18
Q

example of an end product probiotics increase

A

e.g. SCFA

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19
Q

what are the antimicrobial activities of probiotics

A
  • Competition for nutrients, attachment sites on intestinal mucosa
  • Organic acids – some produce lactic acid, production can decrease lumen pH
  • SCFA production
  • Hydrogen peroxide production
  • Bacteriocins production
20
Q

what are bacteriocins

A

biologically active proteins

proteins or peptides

21
Q

what do bacteriocins do

A

antibacterial activity against other species kill other bacteria – kill bacteria that don’t possess the immunity protein

22
Q

is hydrogen peroxide toxic to bacteria

A

can be toxic to some bacteria

23
Q

what are some probiotics used for in gastrointestinal disease

A

Some probiotics used to stop or treat gastrointestinal diseases, e.g.
Antibiotic-associated diarrhoea

24
Q

what has Saccharomyces boulardii been used for

A

reduce antibiotic associated diarrhoea

25
Q

what is L. casei Shirota aka Yakult used to treat

A

reduce SIBO

26
Q

what is lactase

A

enzyme made by the cells lining the villi of small intestine

27
Q

what does lactase do

A

converts lactose to glucose and galactose

28
Q

what is lactase deficiency

A

inability to digest and absorb lactose

29
Q

what is lactose

A

main sugar in milk – a disaccharide

30
Q

what does lactose intolerance cause

A

causes gastrointestinal related symptoms e.g. diarrhoea, flatulence

31
Q

what are the symptoms of lactose intolerance caused by

A

bacteria in the gut fermenting the lactose

32
Q

what bacteria converts lactose to lactate

A

Homofermentative lactic acid bacteria (LAB) can convert lactose to lactate without producing gas

33
Q

what immunomodulation and immunostimulation problems can probiotics be used to treat

A
  • Dysfunctional immune response
  • Food allergy
  • Atopic dermatitis/eczema
  • In some animal models Lactobacillus acidophilus shown anti-tumour activity
34
Q

what is a prebiotic

A

non-digestible food that benefits host, selectively stimulates growth and/or activity of one or limited number of bacteria in the colon, can improve hosts health

35
Q

what is symbiotic

A

Probiotics + prebiotic = symbiotic

involving interaction between two different organisms living in close physical association

36
Q

what are prebiotic typically

A

non-digestible carbohydrate, some peptides/proteins or certain lipids

37
Q

what can prebiotics not be digested by

A

Cannot be digested other than by bacterial activity

38
Q

what must prebiotics be selected for

A

must be chosen to target growth of single/limited numbers of bacterial species in gut

39
Q

what do lactobacillus do

A

They ferment glucose

40
Q

what do homofermenters produce

A

sole product = lactic acid

41
Q

what do heterofermenters produce

A

end products = lactic acid, acetic acid, CO2 and ethanol

42
Q

what does lactobacillus produce

A

bacteriocins
hydrogen peroxide
diacteyl

43
Q

what is diacetyl

A

gives food the ‘buttery’ taste, reported to have antimicrobial properties

44
Q

what is lactobacillus commonly used in

A

food fermentation

45
Q

what is GRAS

A

Generally Regarded As Safe status, easier to pass safety regulations

46
Q

what are the possible problems with probiotic studies

A
  • Strong placebo effect
  • Can be very strain and condition dependent
  • Effects in healthy individuals are hard to detect

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