Pathogenicity Flashcards

1
Q

name the steps of the basic life cycle of a pathogen?

A
  1. enter
  2. attach
  3. colonise
  4. evade host immunity
  5. produce harmful proteins
  6. disseminate
  7. release from host
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2
Q

describe the term pathogen.

A

organism capable of causing disease

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3
Q

describe the term commensal.

A

organism that is part of the normal flora

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4
Q

describe the term pathogenicity.

A

ability to cause disease

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5
Q

describe the term virulence.

A

ability to cause severe disease
eg. more virulent the more dangerous

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6
Q

what are microorganisms?

A

agents of infectious diseases

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7
Q

name 5 divisions of microorganisms?

A

bacteria
fungi
viruses
prions
parasites

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8
Q

what is colonisation?

A

when microbes find a new host and start to multiply

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9
Q

what leads to normal flora?

A

balance between colonised microbes and humans

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10
Q

what is a microbe that causes disease called?

A

infection

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11
Q

what is an endogenous infections?

A

when the source of microbe is a patients own flora

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12
Q

what is an exogenous infection?

A

when the source of microbe is flora from outside a patients body

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13
Q

give characteristics of koch’s postulates?

A
  • microbe must be present in every case of disease
  • microbe must be isolated from diseased host and grown in pure culture
  • disease must be reproduced when a pure culture is introduced into a susceptible host
  • microbe must be recovered from and experimentally infected host
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14
Q

what is koch’s postulates?

A

germ theory of disease

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15
Q

what does koch’s postulates prove?

A
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16
Q

how do microorganisms get into the body person to person?

A
  • contaminated blood or bodily fluids
  • touch
  • saliva
  • air
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17
Q

give 5 examples of how microorganisms get into a person?

A
  • person to person
  • fomites (surfaces)
  • insects
  • water
  • food
18
Q

what is attachment of a microorganisms specific to?

A

host and tissue

19
Q

what allows e coli to attach to the bladder epithelium?

A

pili (fimbriae)

20
Q

describe characteristics of pili (fimbriae) in e-coli?

A
  • proteinaceous
  • usually in gram negative
  • 4-10 nm wide
  • 0.5-4 um long
21
Q

how are pili (fimbriae) in e-coli stuck to a surface?

A

covalently

22
Q

how do UTI’s colonise?

A

faeces or perineal regions

23
Q

who is most commonly after by UTI’s?
and what % of women develop a UTI at some point in their life?

A

females under 10 and between 20-40

50% of woman

24
Q

what is the main defence against UTI’s?

A

flushing action of urine

25
Q

which protein present in urine helps bind specific Escherichia coli strains in UTI’s (helpful)?

A

Tamm-Horsfall protein

26
Q

which fruit helps protect against UTI’s?

A

cranberries

27
Q

give 4 examples of encapsulated infections?

A

meningitis
pneumonia
otitis media
sinusitis

28
Q

what is 4 things that commonly cause encapsulated infections?

A

streptococcus pneumoniae
haemophilus influenza
neisseria meningitis
group B streptococcus

29
Q

what is on the outer layer of a gram positive cell and what does it do?

A

capsule layer
protection

30
Q

what is the capsular function?

A
  • helps mediate adhesion (colonise)
  • helps immune evasion
  • protects from desiccation (doesn’t dry out)
  • receives carbs
  • encapsulated bacteria gives rise to smooth colonies
  • capsule material gives rise to capsular antigens
31
Q

name the 2 types of toxins?

A

exotoxins
endotoxins

32
Q

what are exotoxins?

A

produced inside gram positive bacteria as part of growth and metabolism.
secreted or released following lysis into surround medium.

33
Q

what are endotoxins?

A

part of outer portion of cell wall of gram negative bacteria.
liberated when the bacteria die and the cell wall breaks apart.

34
Q

what are LPS molecules detected by in gram negative?

A

macrophages

35
Q

what is LPS in a gram negative cell wall?

A

lipopolysaccharides

36
Q

is LPS endotoxin or exotoxin?

A

endotoxin

37
Q

when are LPS released from a gram negative cel wall?

A

the cell lises and they are released

38
Q

what is a common syndrome that LPS (endotoxin) can cause?

A

toxic shock

39
Q

what are exotoxins?

A

proteins

40
Q

are exotoxins and endotoxins, specific or non-specific?

A

endotoxins - non specific
exotoxins - specific

41
Q

what is the difference between exotoxins and endotoxins in terms of potency and relationship to cell?

A

endotoxins = low potency, part of outer membrane of cell

exotoxins = high potency, extracellular/ diffusible (made inside and diffused out)