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Mechanisms of Disease > Human microbiota > Flashcards

Human microbiota Flashcards

1
Q

What percentage of cells in the human body are of human origin?

A

10%

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2
Q

What does it mean if a micro-organism is described as ‘virulent’ or ‘pathogenic’?

A

It causes disease

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3
Q

What are Koch’s postulates?

A
  1. The causative organism must be isolated from every individual suffering from the disease in question;
  2. The causative organism must be cultivated artificially in pure culture;
  3. When the causative organism is inoculated from pure culture, the typical symptoms of the infection must result;
  4. The causative organism must be recoverable from individuals who are infected experimentally.
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4
Q

What are the problems with Koch’s postulates?

A

difficulty of isolation of causative agent, impossible to grow some pathogens in artificial culture, ethical objections, animal models not sufficient

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5
Q

What type of parasites are viruses?

A

obligate intracellular parasites

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6
Q

What is the generic structure of a virus?

A

nucleic acid core wrapped in a protein coat (some also have an envelope)

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7
Q

What makes retroviruses unusual?

A

The virion carries an RNA copy of the genome but upon infection of host cell, a cDNA copy of the virus genome is made using the enzyme reverse transcriptase

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8
Q

What is the name of the units making up the protein coat of a virus?

A

capsomeres

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9
Q

Which special class of virus attacks bacteria?

A

bacteriophages

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10
Q

What are believed to cause spongiform encephalopathies?

A

prions

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11
Q

Are all fungi prokaryotic or eukaryotic?

A

eukaryotic

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12
Q

Most fungi have a cell wall made of what?

A

chitin

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13
Q

Define moulds

A

fungi that grow in mats of tiny filaments (hyphae) forming mats called mycelia

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14
Q

What are unicellular fungi?

A

yeasts

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15
Q

Name 2 common superficial infections caused by mould

A

ringworm and athletes foot

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16
Q

Name the 4 classes of protista

A

apicomlexa, flagella Protista, ciliate Protista, amoebae

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17
Q

Name a Protista that can cause vaginal infection

A

trichomonas vaginalis

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18
Q

What do bacterial cells lack?

A

membrane bound nucleus

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19
Q

Are bacteria prokaryotes or eukaryotes?

A

prokaryotes

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20
Q

What are the two most common shapes of bacteria?

A

cocci or bacilli

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21
Q

What does the gram reaction test in bacteria?

A

Their ability to retain a crystal violet-iodine dye complex

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22
Q

What does the envelope of a gram-positive bacteria mainly comprise of ?

A

30-40 layers of peptidoglycan

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23
Q

What is the outer leaflet of gram negative bacteria mainly comprised of?

A

lipopolysaccharide

24
Q

Are gram positive or negative bacteria surrounded by fimbriae?

A

Gram negative

25
Q

What is the function of fimbriae?

A

aid adhesion onto particular surfaces

26
Q

How do gram-negative bacteria exchange genetic material?

A

Through sex pili tubes

27
Q

What is the purpose of a bacterial cell’s capsule?

A

protects the bacterium, even within phagocytes

28
Q

What type of bacteria produce a slime allowing them to stick to plastics?

A

coagulase-negative staphylococci

29
Q

What are endospores?

A

highly resistant structure produced by some bacteria

30
Q

What is a common means of spreading GI infections?

A

faecal-oral route

31
Q

Define fomites

A

inanimate objects that can act as the vectors of infection

32
Q

Define normal flora

A

organisms found in a given location in a state of health

33
Q

Define colonisation

A

establishment at a site in the body

34
Q

Define symbiosis

A

two or more organisms co-exist in close physical association

35
Q

What are the 4 types of symbiosis?

A

mutualism, neutralism, commensalism, parasitism

36
Q

Define mutualism

A

both organisms benefit from symbiosis

37
Q

Define neutralism

A

neither organism derives benefit or harm from symbiosis

38
Q

Define commensalism

A

one organism benefits, while the other does receive not benefit or harm from symbiosis

39
Q

Define parasitism

A

one organism (parasite) benefits at the expense of the other (host_)

40
Q

Define a sterile site and give an example

A

a site with no normal flora, for example to lower respiratory tract

41
Q

How is sterility of sterile sites maintained?

A

surface cleaning, barriers that allow uni-directional flow, physical separation from non-sterile sites

42
Q

What is tissue tropism?

A

cells and tissues of a host which support growth of a particular virus or bacteria

43
Q

Where is coagulase-negative staphylococci found as normal human flora?

A

skin

44
Q

At what sites in the body can staphylococcus aureus be found as normal flora?

A

skin, nostrils, pharynx

45
Q

What is produced in the vagina post-puberty due to circulating oestrogens?

A

glycogen

46
Q

What normal flora is found in the vagina post-puberty?

A

LACTOBACILLUS, skin flora, a few C. albicans

47
Q

What characteristic of the stomach and small intestine prevents bacterial growth?

A

low gastric pH

48
Q

Are the bacteria of the stomach and the small intestine mainly aerobic or anaerobic?

A

aerobic

49
Q

Name the 2 main normal flora found in the stomach and small intestine

A

acid-tolerant lactobacilli and H. pylori

50
Q

Are the bacteria of the large intestine mainly aerobic or anaerobic?

A

anaerobic

51
Q

What prevents overgrowth of pathogens in the large intestines?

A

colonisation resistance by normal gut flora

52
Q

What are the 3 main benefits of normal flora?

A

synthesis and excretion of vitamins, colonisation resistance, induction of cross-reactive bodies

53
Q

What is the main risk factor for clostridium difficile infection?

A

antibiotic treatment

54
Q

What type of treatment has made a ‘come-back’ in treating C.diff?

A

faecal transplants

55
Q

What are the 3 main pathologies of normal flora?

A

overgrowth, translocation, cross-infection

56
Q

Give an example of normal flora overgrowth?

A

vaginal thrush

57
Q

Give an example of a translocation infection

A

conjunctivitis

Mechanisms of Disease (16 decks)

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