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Flashcards in 10 Normal microbiota Deck (18)
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1
Q

How many microbial cells does the human body harbour?

A

10^14

10x the number of human cells

2
Q

Define normal flora and colonisation.

A

Normal flora: organisms food in a given location in a state of health.
Colonisation: establishment at a site in the body.

3
Q

Define neutralism.

A

Neither organism derives benefit or harm from the symbiosis.

4
Q

What is a non-sterile body site?

Which sites are they?

A

No mechanism to maintain sterility.

Conjunctiva, nasopharynx, GI tract, vagina, skin.

5
Q

How is sterility maintained in sterile sites? (3)

Name some examples.

A

Surface cleaning - LRT.
Barriers allowing uni-directional flow - cervix, urethra, eustachian tube.
Physical separation pleural + peritoneal cavity. Spinal cord + meninges.

6
Q

What is tissue tropism in regard to microbiology?

A

Propensity for a particular organism to grow in a particular habitat.

7
Q

What are the skin flora? (3)

A

Coagulase-negative staphylococci (staphylococcus epidermis).
Staphylococcus aureus.
Propionibacterium acnes.
Skin near any orifice may be similar to the orifice.

8
Q

Which micro-organisms are commonly mouth flora? (2)

A

Viridian’s/oral streptococci.

Anaerobes.

9
Q

What is the flora in the pharynx? (5)

A
Streptococcus pyogenes.
Haemophilus influenza.
Streptococcus pneumoniae.
Neisseria meningitidis.
S. aureus.
10
Q

What is the normal flora in the vagina?

How and to what does this change after puberty? (3)

A

Pre-puberty: skin, lower GI (E.coli).
Post: Glycogen present due to oestrogen. Lactobacillus acidophilus ferments glycogen, maintains pH 3. Skin flora + C. albicans.

11
Q

What is the normal flora in the stomach and small intestine?

A

Low pH inhibits growth.
Aerobes: acid-tolerant lactobacilli, H.pylori.
Counts increase distally.

12
Q

What is the normal flora of the large intestine? (8)

A

> 400 organisms.
95-99% anaerobes: Bacteroides, Clostridium, Bifidobacteria.
Aerobes: g-ve bacilli: Escherichia coli, Klebsiella, Enterobacter, Proteus, Citrobacter.

13
Q

What are the benefits of normal flora? (3)

A

Synthesis of vitamins K and B12.
Colonisation resistance by pH generation and antibacterial agents (collisions, bacteriocins, FAs etc).
Induction of cross-reactive antibodies.

14
Q

Which conditions is the micro biome thought to play a role in? (6)

A
IBDs.
Metabolic disorders.
Hypertension.
Obesity.
Cancer.
Infection (especially C.diff).
15
Q

What does C.diff infection lead to? (3)

A

Toxin production.
Diarrhoea.
Pseudomembranous colitis.

16
Q

Which diseases have faecal transplants been suggested for? (7)

A
C. diff (very effective).
MS.
Chronic fatigue syndrom.e
Idiopathic thrombotic purpura.
Ulcerative colitis.
IBS.
Diabetes mellitus.
17
Q

How may normal flora become pathological? (3)

Examples?

A

Overgrowth - thrush.
Translocation - conjunctivitis, intravenous catheter infection.
Cross-infection - MRSA.

18
Q

Which clinical conditions are commonly caused by normal flora? (6)

A
Abscesses.
Dental caries, periodontal disease, pharyngitis.
Pneumonia.
Endocarditis.
Gastroenteritis + peritonitis.
Urogenital infection.