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PHAR20400 > PARADIGMS OF INFECTIOUS DISEASE > Flashcards

PARADIGMS OF INFECTIOUS DISEASE Flashcards

1
Q

What is the definition of virulence?

A

The relative ability of a pathogen to cause disease (measure of pathogenicity)

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2
Q

What do pathogens use to enhance their pathogenicity (3)?

A
  • Virulence factors
  • Toxicity and invasiveness (can determine whether an infection is local or systemic)
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3
Q

What is the definition of attenuation and how does it occur? (3)

A
  • The decrease or loss of virulence
  • Caused by the alteration of favourable growth conditions of an organism, resulting in reduced virulence
  • Can occur naturally or can be caused deliberately when producing a vaccine
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4
Q

What is the definition of toxicity (2)?

A
  • The organism releases a toxin, this toxin inhibits host cell function or kills the host cell
  • The toxin can travel to different sites - this can lead to systemic infection
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5
Q

How to measure virulence (2)?

A
  • Virulence can be estimated from experimental studies of the LD50 (lethal dose50)
  • LD50 is the amount of a agent required to kill 50% of a test group
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6
Q

What is the definition of invasiveness?

A
  • Ability of a pathogen to grow in host tissue at densities that inhibit host function
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7
Q

When a pathogen enters a host, what is it called? Also, how do pathogens spread after entering the host?

A
  • Adherence - entry of the pathogen into the host
  • Spreads throughout the host via circulatory or lymphatic systems
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8
Q

Give two examples of anatomical virulence factors of a bacterial cell?

A
  1. Capsule - Protects bacterial cell and allows the organism to invade the immune system
  2. Pili (proteinaceous structures)- Allows attachment of bacteria to host cells and prevents organisms from being washed away
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9
Q

What is the definition of a non-invasive pathogen (4)?

A
  • Involves viable bacteria1 but the bacteria doesn’t penetrate the epithelial layer2
  • Localised at point of entry3 or mediated by exotoxins4
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10
Q

What are some examples of non-invasive pathogens? (3)

A
  1. Diptheria
  2. Whooping cough (pertussis)
  3. Cholera
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11
Q

What’s the causative agent of Diptheria?

A

Corynebacterium diphtheriae - inhaled

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12
Q

What’s the morphology of Diptheria? (3)

A
  • Gram-positive
  • Non-motile
  • Clubbed morphology
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13
Q

What’s the clinical presentation of Diptheria? (3)

A
  • Pseudomembrane (throat)
  • Difficulty swallowing
  • Systemic effects – heart complications, coma, death
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14
Q

What’s the pathogenesis (how can it cause disease) of Diptheria?

A

Production of AB toxin inhibits EF2 which prevents protein synthesis and kills the cell

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15
Q

What’s the causative agent of Whooping cough (pertussis)?

A

Bordetella pertussis

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16
Q

What’s the morphology of Whooping cough (pertussis)? (3)

A
  • Gram-negative
  • Aerobic cocco-bacillus
  • Confined to humans
17
Q

What’s the clinical presentation of Whooping cough (pertussis)? (3)

A
  • Paroxysms of cough (whoop)
  • CNS effects
  • Secondary pneumonia
18
Q

What is the pathogenesis (how it cause disease) of Whooping cough (pertussis)? (4)

A
  • Attachment and replication on ciliated URT mucosa
  • Produces pertussis exotoxin, tracheal cytotoxin and invasive adenylate cyclase toxin
19
Q

What’s the causative agent of Cholera?

A

Vibrio cholera

20
Q

What’s the morphology of the causative agent of Cholera? (2)

A
  • Comma shaped
  • Gram-negative
21
Q

What’s the clinical presentation of Cholera?

A
  • Infects small intestine causing rice water stools
22
Q

What is the pathogenesis (how it cause disease) of Cholera?(4)

A

Cholera toxin1 increases adenylate cyclase activity2 which causes excess salt and water movement into the lumen of the small intestine3,death by dehydration4

23
Q

What is meant by a partially-invasive pathogen?(3)

A

Invade epithelial layer1 but don’t penetrate deeper tissue2. They invade at primary site of infection only3

24
Q

Give an example of a disease caused by a partially invasive pathogen and name it’s causative agent(s)? (3)

A

Shigellosis
Causative agent:

  1. Shigella sonnei – mild infections
  2. Shigella flexneri – severe infections
  3. Shigella dysenteriae – very severe
25
Q

What’s the morphology of the causative agent of Shigellosis? (3)

A
  • Gram-negative rods
  • Facultative anaerobes
  • Non spore forming
26
Q

What’s the clinical presentation of Shigellosis?

A

Blood and puss in diarrhoea

27
Q

How do primary invasive pathogens spread?

A

Enter lymphatic system from a primary infection site

28
Q

What is the pathogenesis (how it cause disease) of Shigellosis?

A
  • Attachment and invasion of distal ileum and colonic epithelia
  • Shiga toxin (an AB toxin)
29
Q

Give an example of a disease caused by a primary invasive pathogen and name it’s causative agent?

A

Disease: Enteric fever (typhoid)

Causative agent: Salmonella enterica serovar Typhi

30
Q

What’s the clinical presentation of Enteric fever (typhoid)? (4)

A
  • Systemic infection
  • Constipation/diarrhoea
  • Fever
  • 3 week symptom duration (3% become chronic carriers)
31
Q

How is Enteric fever (typhoid) transmitted?

A
  • Person to person spread
  • Consumption of contaminated foods (infection of small intestine)
32
Q

What is the pathogenesis of Enteric fever? (2)

A
  • Primary infection via Jejunum or Distal Ileum (e.g. Small intestine) and is uptaken via M cells in the intestines
  • Travel through epithelia into the bloodstrean (systemic dissemination)
    • Macrophage can be the vehicle in which the organism moves through the body
33
Q

Give examplesof diseases that don’t have bacterial colonization (3) and explain why they’re able to cause disease?

A
  • Clostridium botulinum, Staphylococcus aureus and
  • They cause disease because the food contains toxins (chemical or bacterial origin)
34
Q

What’s the morphology of the causative agent of Botulism? (2)

A
  • Obligately anaerobic
  • Spore forming
35
Q

Where is Staphylococcus aureus found?

A

Creamy foods and custards

36
Q

What causes the symptoms (nausea, abdominal pain) of Staphylococcus aureus? (3)

A
  • S aureus produces an enterotoxin
  • When ingested, S aureus interacts with the gastric mucosa
  • Symptoms are produced
37
Q

What is the morphology of Bacillus cereus? (2)

A

Obligately aerobic but spore forming bacterium

38
Q

What are the two disease forms of Bacillus cereus?

A
  1. Emetic toxin - heat stable, short incubation
  2. Enterotoxin (Nhe and HBL) - heat labile, longer incubation, cause diarrhoea

PHAR20400 (20 decks)

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