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Microbiology > M3- Koch's postulates - basis of infectious disease I > Flashcards

M3- Koch's postulates - basis of infectious disease I Flashcards

1
Q

what is Koch’s postulates germ theory of disease?

A
  • the microorganism is present in every case of the disease but absent from healthy organisms
  • the suspected organism must be isolated and grown in a pure culture
  • the same disease must result when the isolated microorganism is inoculated into a healthy host
  • the same microorganism must be isolated again from the diseased host
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2
Q

Name some infectious agents.

A
  • bacteria- prokaryotic, single celled organisms
  • viruses- non-living, obligate parasites
  • fungi- eukaryotic single to multi-cellular infectious agents
  • protozoa- amoeba
  • parasites
  • prions -infectious proteins
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3
Q

what is the microbiome?

A

community of cells that are not part of our body directly

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4
Q

what is AMR?

A

antimicrobial resistance

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5
Q

what are endogenous micro-organisms?

A

microorganisms within the body

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6
Q

what are exogenous microorganism?

A

comes from outside the body ( not normal flora)

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7
Q

What is free living organism?

A
  • found in soil

- feed on dead organic material

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8
Q

what is commensal organism?

A

organism gains advantage but host does not gain from association

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9
Q

What is mutualistic organism?

A

(symbiotic) relationship , when host and organism gain mutal value

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10
Q

what is parasitic organism?

A

live on or in living creatures causing harm/damage to the host

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11
Q

what is the relationship between bacteria in a mutualism state to parasitic state?

A

dynamic relationship (bacteria can shift to becoming parasites)

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12
Q

Describe the mutualistic relationship.

A
  • organism can produce nutrients or vitamins
  • can degrade harmful chemicals
  • can exclude access/colonisation by exogenous pathogens (colonisation resistance)
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13
Q

what limits microorganisms colonising?

A

shedding of surface epithelium

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14
Q

what makes up the oral microbial flora?

A
  • mucosa of lips, cheeks and palate
  • tongue
  • tooth surfaces
  • saliva
  • tonsillar area
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15
Q

what oral microbial flora is the only naturally non-shedding community in the body?

A

teeth

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16
Q

what makes oral microbial sampling difficult?

A
  • stimulated /non-stimulated salvia
  • mucosal surfaces -difficult to swab
  • plaque
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17
Q

what controls many commensals?

A

antibodies

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18
Q

what can precipitate disease?

A
  • change in state

- (broad spectrum antibiotics disturb microflora)

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19
Q

what is the definition of pathogen?

A
  • a harmful organism that produces a pathology

- virulence and its factors

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20
Q

what is the definition of commensal?

A
  • an organism that is part of the normal flora
  • often mutualistic relationship
  • endogenous
21
Q

what is the definition of opportunistic pathogen?

A

-an organism that causes infection when opportunity / change in natural immunity arises e.g. in an immunocompromised individual

22
Q

what is the definition of contaminant?

A

an organism that is growing in a culture by accident

23
Q

what is virulence?

A

the capacity of a microbe to cause damage to the host

24
Q

Name the virulence factors.

A
  • Adhesin
  • Invasin
  • Impedin
  • Aggressin
  • Modulin
25
Q

what effect does adhesion have?

A

enables binding of the organism to host tissue

26
Q

what effect does invasin have?

A

enables the organism to invade a host cell/tissue

27
Q

what effect does impedin have?

A

enables the organism to avoid host defence mechanisms

28
Q

what effect does aggressin have?

A

causes damage to host directly

29
Q

what effect does moulin have?

A

induces damage to the host indirectly

30
Q

What is molecular koch’s postulates?

A

-A virulence trait should be strongly associated with pathogenic strains of the species
• Inactivation of gene(s) associated with the virulence trait should decrease pathogenicity
• Restoration of an inactivated/mutated gene with the wild type restores pathogenicity
• The gene is expressed at some point during infection.
• Antibodies directed against the gene product protect the host

31
Q

what are the limitations?

A
  • organism cannot be cultured/isolated -obligate intracellular organisms
  • organism is a human pathogen- no model organisms to inoculate
32
Q

what is the definition of obligate pathogens?

A

must cause disease for transmission

33
Q

what is the definition of the opportunistic pathogens?

A

Do not have to cause disease for transmission

34
Q

what is the definition of “accidental” pathogens?

A

disease hinders or prevents transmission (host death)

35
Q

what is the only method of transmission of an obligate pathogens?

A

human disease

36
Q

what is epidemiology?

A

the study of the occurrence , spread and control of disease

37
Q

what is considered for any organism?

A
  • infective dose
  • virulence of the organism
  • host status (resistance)
38
Q

what is sporadic occurrence?

A

comes and goes in low numbers -occassionally it occurs

39
Q

what is endemic occurrence?

A

present all the time in population but in low levels i.e common cold

40
Q

what is epidemic occurrence?

A

sudden increase in disease in a location of a period time

41
Q

what is pandemic occurrence?

A

same as epidemic but geographical concept - 2 or more contenants

42
Q

what is prevalence?

A

proportion of population affected

43
Q

what is retrospective?

A

clinical effect studied

44
Q

what is prospective?

A

population exposed to presumed cause studied

45
Q

what is microbiota/flora?

A

endogenous population of microbes

46
Q

what is Koch’s postulates?

A

basis for demonstrating cause of disease

47
Q

what is pathogenicity?

A

capacity to cause disease/damage

48
Q

what is resistance?

A

ability to resist anti-infective measures

Microbiology (30 decks)

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