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

Question 1

what is Koch’s postulates germ theory of disease?

Answer 1

• 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

Question 2

Name some infectious agents.

Answer 2

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

Question 3

what is the microbiome?

Answer 3

community of cells that are not part of our body directly

Question 4

what is AMR?

Answer 4

antimicrobial resistance

Question 5

what are endogenous micro-organisms?

Answer 5

microorganisms within the body

Question 6

what are exogenous microorganism?

Answer 6

comes from outside the body ( not normal flora)

Question 7

What is free living organism?

Answer 7

• found in soil

- feed on dead organic material

Question 8

what is commensal organism?

Answer 8

organism gains advantage but host does not gain from association

Question 9

What is mutualistic organism?

Answer 9

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

Question 10

what is parasitic organism?

Answer 10

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

Question 11

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

Answer 11

dynamic relationship (bacteria can shift to becoming parasites)

Question 12

Describe the mutualistic relationship.

Answer 12

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

Question 13

what limits microorganisms colonising?

Answer 13

shedding of surface epithelium

Question 14

what makes up the oral microbial flora?

Answer 14

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

Question 15

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

Answer 15

teeth

Question 16

what makes oral microbial sampling difficult?

Answer 16

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

Question 17

what controls many commensals?

Answer 17

antibodies

Question 18

what can precipitate disease?

Answer 18

• change in state

- (broad spectrum antibiotics disturb microflora)

Question 19

what is the definition of pathogen?

Answer 19

• a harmful organism that produces a pathology

- virulence and its factors

Question 20

what is the definition of commensal?

Answer 20

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

Question 21

what is the definition of opportunistic pathogen?

Answer 21

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

Question 22

what is the definition of contaminant?

Answer 22

an organism that is growing in a culture by accident

Question 23

what is virulence?

Answer 23

the capacity of a microbe to cause damage to the host

Question 24

Name the virulence factors.

Answer 24

• Adhesin
• Invasin
• Impedin
• Aggressin
• Modulin

Question 25

what effect does adhesion have?

Answer 25

enables binding of the organism to host tissue

Question 26

what effect does invasin have?

Answer 26

enables the organism to invade a host cell/tissue

Question 27

what effect does impedin have?

Answer 27

enables the organism to avoid host defence mechanisms

Question 28

what effect does aggressin have?

Answer 28

causes damage to host directly

Question 29

what effect does moulin have?

Answer 29

induces damage to the host indirectly

Question 30

What is molecular koch's postulates?

Answer 30

-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

Question 31

what are the limitations?

Answer 31

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

Question 32

what is the definition of obligate pathogens?

Answer 32

must cause disease for transmission

Question 33

what is the definition of the opportunistic pathogens?

Answer 33

Do not have to cause disease for transmission

Question 34

what is the definition of "accidental" pathogens?

Answer 34

disease hinders or prevents transmission (host death)

Question 35

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

Answer 35

human disease

Question 36

what is epidemiology?

Answer 36

the study of the occurrence , spread and control of disease

Question 37

what is considered for any organism?

Answer 37

- infective dose - virulence of the organism - host status (resistance)

Question 38

what is sporadic occurrence?

Answer 38

comes and goes in low numbers -occassionally it occurs

Question 39

what is endemic occurrence?

Answer 39

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

Question 40

what is epidemic occurrence?

Answer 40

sudden increase in disease in a location of a period time

Question 41

what is pandemic occurrence?

Answer 41

same as epidemic but geographical concept - 2 or more contenants

Question 42

what is prevalence?

Answer 42

proportion of population affected

Question 43

what is retrospective?

Answer 43

clinical effect studied

Question 44

what is prospective?

Answer 44

population exposed to presumed cause studied

Question 45

what is microbiota/flora?

Answer 45

endogenous population of microbes

Question 46

what is Koch's postulates?

Answer 46

basis for demonstrating cause of disease

Question 47

what is pathogenicity?

Answer 47

capacity to cause disease/damage

Question 48

what is resistance?

Answer 48

ability to resist anti-infective measures