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Infection and Immunology > Bacterial infection 1 > Flashcards

Bacterial infection 1 Flashcards

1
Q

Infection

A

Microbe is established in a host

May not involve disease or any symptoms
Can lead to disease

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2
Q

Nosocomial infections

A

Acquired in hospital

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3
Q

Disease

A

Infection causes damage or pathology to host

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4
Q

Pathogenesis

A

Sequence of events + mechanisms + processes that cause disease

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5
Q

Catheter associated UTI

A

Often nosocomial

Often asymptomatic + infected unless serious complications arise

Encrustation + blockage issues

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6
Q

Latent TB

A

TB lives but doesn’t grow in body
Asymptomatic
Can’t spread between people
Can advance to TB disease

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7
Q

TB disease

A

Active + grows in body
Symptomatic
Can spread between people
Fatal if untreated

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8
Q

Dynamic balance between health + disease

- disease factors

A

Pathogen exposure
Routes of transmission
Pathogen load
Site of pathogen exposure

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9
Q

Dynamic balance between health + disease

- health factors

A 
Immune status 
Nutrition 
Vaccination 
Sanitation 
Injury 
Ageing 
Medical devices
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10
Q

Parasite

A

Org that colonises host + causes harm

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11
Q

Primary pathogens

A

Breach defences + cause disease in a healthy host

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12
Q

Opportunistic pathogen

A

Cause disease in compromised host

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13
Q

Pathogenicity

A

Ability to cause disease

  • combines infectivity + virulence
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14
Q

Virulence

A

Measure indicating severity of a disease

e.g. LD50 for lethal pathogens

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15
Q

LD50

A

= Lethal dose 50%

No. of orgs (cells/virions) required to kill 50% of hosts in a test group

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16
Q

How do infections begin?

A

Exposure to a pathogen

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17
Q

Route of transmission

A
  1. Exposure
  2. Adherence
  3. Invasion
  4. Infection
    (can lead to further exposure at local sites)
  5. Toxicity or Invasiveness (can lead to further exposure)
  6. Tissue damage + disease
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18
Q

Transmission

A

Horizontal - indirect or direct
Vertical
Vehicle
Insect vectors

19
Q

Horizontal indirect transmission

A

Inanimate objects (fomites), vehicle transmission or an insect vector

20
Q

Horizontal direct transmission

A

By direct contact or aerosolisation e.g. sneeze

21
Q

Vertical transmission

A

An insect can transmit an infectious agent to its offspring

22
Q

Vehicle transmission

A

Inanimate objects

- e.g. fomites, food, water, air

23
Q

Virulence factors

A

Bacterial traits that facilitate infection

e.g. toxins, effector proteins , biofilm formation, adhesion

24
Q

Molecular Koch’s postulates

A

= set of criteria that must be met to show a gene in a pathogen encodes a product that will contribute to disease

25
Q

Molecular Koch’s postulates

- trait should be associated w/ a pathogenic strain

A

Inactivation of suspected virulence gene
-> should lead to measurable loss in virulence

Replacement of inactive gene w/ function copy should restore virulence (measure using LD50)

26
Q

After exposure

A

Pathogen finds site of colonisation

- stays there via attachment mechanisms

27
Q

Innate defences role

A

Try to exclude + clear bacteria before they can cause disease

28
Q

Innate defences

e.g.s

A

Mucociliary escalator + microflora

All mucosal sites have fluid flow + resident microflora

Peristalsis in intestine

Stomach acid

29
Q

Adhesion

A

To avoid clearance mechanisms

- stick to hosts (often mucosal surfaces)

30
Q

Adherence molecules

A

Pili
= specific specialised structures

Adhesions
= range of proteins + molecules

31
Q

Pili

A

Repeating subunits assembled on cell surface

Proteins at top vary to recognise different host cell receptors

Adhesin at tip

32
Q

Pili

- common e.g.s produced by pathogenic bacteria

A

Type 1 + Type 4

Type 4 can retract

  • pull bacteria closer to host
  • twitching motility
  • disrupt tight junctions between cells
33
Q

Pili

- interactions

A

Doesn’t provide close cell-cell contact

34
Q

Pili

+ adhesins

A

Bind to components present on host cells
- via hydrophobic or charge interactions,
or receptor-ligand interactions (specific binding)

35
Q

E.coli EPEC

  • name
  • virulence factors
A

= Enteropathogenic E. coli

Attaching lesions
Pedestal formation

36
Q

Pathovars

A

Pathogenic strains grouped based on their disease characteristics

37
Q

E.coli EPEC

  • route of transmission
  • reservoirs
  • colonisation
A

Faecal-oral route of transmission
- via contaminated food/surfaces

Animals

Colonise intestinal tissues facilitated by type 4 pili
+ systems to promote close contact w/ epithelial cells

38
Q

E.coli pathovars

A

Virulence capabilities of pathovars largely determined by acquisition of PAIs

39
Q

PAIs

A

Pathogenicity Islands
= clusters of genes that encode for various virulence factors

Can be transferred between strains or species

40
Q

Pili affects…

A

Host range

Sites of infection within hosts

41
Q

EPEC features

A

35kb PAI
= LEE

adhere to gut epithelia tissue

form micro colonies + attaching lesions

LEE encodes Initimin/TIR proteins

42
Q

EPEC adhesion to epithelial cells in intestine

A

Pili interact w/ N-acteyl-lactosamine- containing receptors on host cells

Pili also important for EPEC self-interactions
-> micro colonies

Retraction of Type 4 pili

  • > cells closer
  • > LEE system can work effectively
43
Q

Intimin

A

OM protein made by EPEC strains

BUT no natural receptor in host cells so EPEC produces + injects Tir via T3SS

44
Q

Tir

A

= Translocated intimin receptor

Localises to membrane + provides receptor for Initmin
-> pedestal formation triggered

Infection and Immunology (13 decks)

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