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PHA 223 > micro 4 > Flashcards

micro 4 Flashcards

1
Q

how do microbial communities vary?

A

vary by site on the body

- environmental conditions and nutrient availability

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2
Q

where is there a high and a low bacterial density in the GI tract?

A 
high= colon (large intestine)
low= small intestine and stomach
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3
Q

what is the ph in the small intestine, stomach and colon?

A

small intestine- 6.5-7.5
stomach-1-2
colon 5-7

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4
Q

what is the aerobica conditions like in the small intestines, stomach and colon?

A

small intestine= dec oxygen content
stomach= oxygen present
solon= anaerobic

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5
Q

what part of the GI tract has the largest and the smallest bacterial density?

A

smallest= stomach -10^1-3

largest=colon 10^10-13

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6
Q

what is the bacterial diversity like in the small intestine?

A
  • Low bacterial diversity
  • Facultative anaerobes
  • Streptococcus, Lactobacillus, Enterobacteriaceae
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7
Q

what is the bacterial diversity like in the stomach?

A
  • Relatively low bacterial diversity

* Mainly Streptococcus and Lactobacillus

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8
Q

what is the bacterial diversity like in the colon?

A
  • High bacterial diversity
  • Particularly anaerobes
  • Clostridia
  • Bacteriodes
  • Bifidobacterium
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9
Q

why do we need a gut microbiome?

A

when healthy a balance between good and bad microorganisms is maintained which help protect against infectious deiseaes
- they also contribute to metabolism

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10
Q

how does a good microbiome contribute to metabolism?

A

provides certain nutrients which humans cannot provide normally
- •Breakdown of non-digestible substrates (e.g. dietary fibre and intestinal mucus)•Production of short chain fatty acids (e.gacetate, propionate and butyrate)
•Amino acid metabolism (e.g. Tryptophan)
•Vitamin production (e.gB10; para-aminobenzoic acid)

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11
Q

is the GI of a foetus sterile?

A

it was assumed so- but there is data to suggest that it maternal microbes can eneter fetus GI tract- seen in first meconium (poo)

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12
Q

what is GI tract microbiota and gestational age related to?

A

associated with gut microbiota abundance and diversity

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13
Q

how is type of birth linked to difference in initial microbiome?

A
  • vaginal birth derived from vaginal microbiome

- caesarean section derived from maternal skin(e.g. Staphylococcus, Propionibacterium)

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14
Q

what is the core microbiome for gestation/ parturation, infancy, puberty, adulthood, old age?

A 
1- facultative anaerobes, proteobacteria
2-bacteroides, bifidobacterial
3- firmicutes, Bacteroides
4-bacteroides, firmicutes
5- obligate and facultative anaerobes
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15
Q

what are probiotics?

A

they are a chemical substrate that is selectively used by a host microorganism to produce a healthy benefit

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16
Q

what criterial do prebiotics have to meet?

A
  • Non digestible and resistant to breakdown by stomach acid and human enzymes
  • Selectively fermented by intestinal microorganisms
  • Selectively target and stimulate growth/activity of beneficial bacteria
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17
Q

what are bacterial targets for prebiotic substrates?

A

Bifidobacteria and Lactobacilli

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18
Q

are all prebiotics fibre?

A

yes but not all fibre is prebiotic

19
Q

what are probiotics?

A

re live cultures of miroorganisms promoted with health benefits claims;

20
Q

what are 2 examples of probiotic microbacteria?

A

•Lactobacilli and bifidobacteria

21
Q

how do probiotics work?

A 
a- co-aggregation
b-biocirfactant production
c- bacteiocin and H2O2 production
d-signalling effects
e-competitive exclusion
f-immunomodulation
g-modulation of tight junctions
22
Q

do probiotics work?

A

high quality evidence but not scientificially proven- states that they are not intended
to diagnose, treat, cure, or prevent any disease.

23
Q

how is gut microflora disrupted by antibiotics?

A

•Susceptible cells killed indiscriminately

24
Q

what can misuse of antibiotics lead to in gut microflora?

A
  • Growth of resistant subpopulation
  • Removal of repressing microorganisms
  • Lead to secondary infections
25
Q

how long aprox does it take for gut microflora to return to normal after antibiotics?

A

40 days-some still missing

composition still different

26
Q

what is faecal microbial transplants?

A
  • Basic idea is to transplant faecal microbes from healthy individual to a recipient
  • Usually taken from parent/partner etc
  • Can also be autologous
  • Needs to be screened for pathogens!•Has been used to treat patients with CDI
27
Q

what non-infectious diseases has gut-microbiome been linked to?

A

obesity

depression

28
Q

how is helicobacter pylori linked to gut microbiota?

A
  • linked to stomach ulcers/peptic ulcer disease

- risk factor for gastric cancer

29
Q

what type of bacteria is h.pylori?

A

gram negative, curved rod, microaerophilic

30
Q

what strains of h.pylori have a pathogenicity island?

A

CagPAI
- 40kn of DNA encoding for 31 genes
absent from non-pathogenetic strains

31
Q

how do h.pylori survive and colonise?

A
  • Uses flagella to swim into the mucus lining
  • Breaks down urea
  • Sticks tightly to stomach epithelial cells
32
Q

does h.pylori perfer a more acidic or basic environment?

A

perfers less acidic- swim away using flagella

33
Q

how does h.pylori produce urease?

A

produces urease
creates a bufffer zone of higher ph
its also toxic
may help recruit neutrophils to mucosa

34
Q

what happens when T4SS from cagPAI injects Cag into GEC cytosol?

A
  • Once inside its phosphorylated by Srcand Ablkinases
  • Interacts with host cell proteins with have SH2 domains
  • Produces cytoskeleton rearrangement
  • Deregulates some signal transduction pathways
35
Q

how commmon is CAGA?

A

is the 4thmost abundant protein produced by H. pylori

•Suggests that large amounts needed to have an effect

36
Q

what is cagA associated with?

A

•Associated with ↑ Inflammation and more severe disease outcomes

37
Q

what role does VACA play?

A
  • Vacuolating cytotoxin (VacA) hypothesised in 1988

* Proteinaceous component of H. pyloriculture supernatant vacuolated cultured eukaryotic cells

38
Q

where is vacA present?

A

A single intact vacAgene present in all H. pylori strains

•Also present in H. cetorumstrains

39
Q

what does vacA do in cells?

A
  • Can enter cells but doesn’t have enzymatic activity
  • Can form anion selective membrane channels
  • Cl-, HCO3-, small organics
  • Can potentially cause cell death by altering mitochondria
40
Q

how can vacA affect the immune system?

A
  • Inhibits activation of T and B-cells
  • Impaired macrophage engulfment
  • Can stimulate expression of COX-2 in macrophages and neutrophils (↑ proinflammatory)
41
Q

how do you diagnose h.pylori?

A 
serology
urea breath test
faecal antigen testing
rapid urease test
histology
42
Q

how do you treat h.pylori?

A
  • PPI
  • Antibiotics
  • No penicillin allergy: Amoxicillin AND either clarithromycin or metronidazole
  • Penicillin allergy: Clarithromycin AND metronidazole
43
Q

what are gut virome?

A
  • These viruses have a role to play
  • Vectors for gene transfer
  • Non-host based antibacterial defence
44
Q

what are examples of pro and euk gut vurome?

A
  • Prokaryotic(e.g. CrAssphage and Microviridae bacteriophages). THESE MAKE UP THE MAJORITY •Eukaryotic
  • Commensal viruses which can cause disease (e.g. Adenoviridae)•Disease causing (e.g. Rotavirus in some individuals)

PHA 223 (42 decks)

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