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MD2001 NG > intro to microbial infection > Flashcards

intro to microbial infection Flashcards

1
Q

4 barriers to entry of the immune system

A

normal microbiota
physical barriers
chemical barriers
phagocytes

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2
Q

what is the normal microbiota?

A

this is the microorganisms that reside in the tissue and skin

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3
Q

what does the microbiota do?

A
  • they offer protection by competing with pathogens
  • they produce antibiotic substances
  • they produce toxic metabolic products
  • may alter pH
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4
Q

what will the normal microbiota be suppressed by?

A

antibiotics

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5
Q

what are the examples of physical barriers?

A

skin - secretes sebum and fatty acids that inhibit growth
mucus clearance
flushing - pee, tears, sweat
peristalsis - moves waste out of the body preventing biofilms forming.

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6
Q

what are examples of chemical barriers?

A

mucus
antimicrobial proteins
gastric acid
plasma proteins

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7
Q

what is bacterial growth and survival dependant on?

A

upon the ability of an organism to sense its environmental conditions and respond to external stimuli

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8
Q

what are the 2 ways infection happens?

A

invading host tissue
exerting effects from mucosal surface

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9
Q

when does an infection occur

A

when a microorganism causes ill health

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10
Q

what is disease?

A

the damage to cells, tissues and organs that causes dysfunction

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11
Q

what are the 6 things that may cause disease?

A
  • bacterial
    fungal
    viral
    protist
    macro parasite
    prion
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12
Q

commensal

A

a micro organism that forms part of the hosts normal microbiota

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13
Q

pathogen

A

an organism that causes disease

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14
Q

pathogenicity

A

the capacity to cause disease

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15
Q

pathogenesis

A

the development of disease

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16
Q

virulence

A

a measure of the capacity to cause disease

17
Q

what are the 3 types of pathogen?

A

obligate pathogen = almost always associated with disease
conditional pathogen = may cause disease if certain conditions are met
opportunistic pathogen = usually only effects an immune compromised host

18
Q

what are the 6 steps in infection?

A

1- recognition
2- attachment and entry
3- multiplication
4- evasion of host defences
5/6- shedding and damage

19
Q

what are the 4 ways infection can be established in a healthy host?

A

1- microbes with mechanisms for attachment and penetration
2- microbes introduced to host by biting arthropods
3- microbes introduced to host via skin wounds
4- microbes only able to infect when host defences are impaired

20
Q

what is tissue tropism?

A

the affinity of the microbe for a specific tissue
defines the tissue that supports the growth of the microbe

21
Q

do all microbes have the same tropism?

A

no, some have a broad range of cells and tissues they will infect, others can be very specific.

22
Q

what are the influencing factors for tissue tropism?

A
  • presence of cell receptors
  • transcription factors
  • temp
  • physical barriers
  • ph
23
Q

what cell will varicella zoster virus infect?

A

nerve cells

24
Q

what cells will HBV infect

A

liver cells

25
Q

what cells will helicobacter pylori infect?

A

gastric mucosa

26
Q

what cells will HIV infect

A

t lymphocytes

27
Q

what cells will neisseria meningitides infect?

A

nasopharyngeal epithelium

28
Q

where will the influenza virus attach?

A

to cilia and microvilli on the tracheal epithelium

29
Q

what cells will the vibrio cholerae infect?

A

villi of intestinal epithelium

30
Q

what are the factors that favour good virulence?

A
  • toxin secretion (bacteria and fungi)
  • antibiotic resistance
  • pilus formation
  • capsule
  • iron transport systems
  • adhesion factors
  • enzymes
31
Q

describe endotoxins

A
  • low toxicity
  • part of the cell wall of gram negative
  • low specificity
  • found in lipopolysaccharide area
32
Q

describe exotoxins

A
  • highly toxic
  • secreted from bacterial cells
  • produced by gram positive and negative
  • can be converted into toxoids for vaccine use
33
Q

what are the factors that favour antibiotic resistance for a microbe?

A
  • resistance genes on plasmids
  • production of enzymes
  • impermeability
  • efflux mechanisms
  • alteration of target site
34
Q

what 3 factors does transmission depends on?

A

1- the number of micro organisms shed
2- the number of micro organisms required to infect
3- the micro organisms stability in the environment

35
Q

fomite transmission

A

via an inanimate object

36
Q

what are the 2 types of vectors in animal to human transmission

A

invertebrate vectors - arthropods and shellfish
vertebrates - mammals and birds

MD2001 NG (28 decks)

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