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262A Oral Biology > Microbiology - NH > Flashcards

Microbiology - NH Flashcards

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1
Q

What is a bacterial pathogen of the upper respiratory tract? What disease(s) does it cause?

A

L15
Streptococcus pneumoniae
- causes sinusitis and Otitis media (OM)

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2
Q

What are the virulence factors of Streptococcus pneumoniae?

A

L15

  • alpha-haemolytic: partial lysis RBC
  • capsule: prevents complement activation
  • cell wall adhesins: endothelial cell adhesion
  • pneumolysin: cytolytic and cytotoxic
  • autolysin: self-destruct protein
  • neuroamidase: expose receptors for adhesion
  • IgA1 protease: cleaves IgA antibodies + evades mucosal immune system
  • hydrogen peroxide: toxic to cells
  • competence: ability to take up DNA + antigenic variants
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3
Q

How is alpha-haemolysis a virulent factor of S. pneumoniae?

A

L15

- partially lyses RBC

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4
Q

Why is the capsule a virulent factor for S. pneumoniae?

A

L15

  • prevents activation of complement cascade
  • low antigenicity
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5
Q

Why are cell wall adhesins a virulent factor of S. pneumoniae?

A

L15

- endothelial cell adhesion

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6
Q

Why is pneumolysin a virulent factor of S. pneumoniae?

A

L15

  • cytolytic and cytotoxic exoprotein
  • binds Fc portion of antibodies
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7
Q

Why is autolysin a virulent factor of S. pneumoniae?

A

L15

  • self-destruct protein
  • releases cell contents
  • i.e. more toxins
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8
Q

Why is neuramidase a virulent factor of S. pneumoniae?

A

L15

- expose receptors for adhesion

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9
Q

Why is IgA1 protease a virulent factor of S. pneumoniae?

A

L15

  • cleaves secretory IgA antibodies
  • evades mucosal immunity
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10
Q

why is competence a virulent factor of S. pneumoniae?

A

L15

  • ability to take up DNA from environment
  • modify genetic structure = antigenic variants of the capsule
    i. e. change surface proteins to evade immune response
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11
Q

Why is hydrogen peroxide a virulent factor of S. pneumoniae?

A

L15

- toxic to cells

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12
Q

What types of virulence factors allow a microbe to be a successful pathogen?

A

L15

  • ability to adhere to and colonise the host
  • adapt to the environmental changes within the host
  • avoid host defence system
  • be able to defeat the host defence system
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13
Q

What are the virulence factors of Mycobacterium tuberculosis? Why do they contribute to pathogenicity of M.tb?

A

L16

  • mycolic acid (waxy layer) on cell wall: resists desiccation
  • grows slowly: common antibiotics (penicillin) are ineffective
  • resistant to lysis agents: can grow inside phagocytes
  • produce cord factor: increase survival within the host
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14
Q

Why is mycolic acid a virulent factor of M.tb?

A

L16

it is a waxy layer on the cell wall and enables resistance to desiccation

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15
Q

Why is slow growth a virulent factor of M.tb?

A

L16

means that common antibiotics (penicillin) are ineffective

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16
Q

Why is resistance to lysis agents a virulent factor of M.tb?

A

L16

- enables bacteria to grow inside the phagocytes

17
Q

Why does production of cord factor contribute to the virulence of M.tb?

A

L16

  • increases the survival of the bacteria in the host
  • strains that do not produce cord factor are less virulent
18
Q

What infections does Staphylococcus aureus cause?

A

L17

  • folliculitis
  • scalded skin syndrome
19
Q

What are the virulence factors of S. aureus and what do they do?

A

L17
enzymes:
- coagulase: clots blood
- hyaluronidase: breaks down hyaluronic acid
- staphylokinase: breaks down blood clots
- lipases: break down lipids
- beta-lactamase: destroys beta-lactam antibiotics (penicillin)
anti-phagocytic defences:
- polysaccharide slime layer (capsule): prevents phagocytosis + enables adherence
- protein A: binds to antibody stems = prevents phagocytosis + complement activation
toxins:
- cytolytic toxin: disrupts cell membranes
- leukocidin: kills leukocytes (WBC)
- exfoliative toxin: breaks down desmosomes
- Toxic Shock Syndrome toxin: superantigen

20
Q

How does coagulase contribute to the virulence of Staphylococcus aureus?

A

L17

  • clots blood
  • camouflages from phagocytes
21
Q

How does hyaluronidase contribute to the pathogenicity of S. aureus?

A

L17

  • degrades hyaluronic acid
  • hyaluronic acid is a major component of cell-cell matrix
  • allows bacterium to spread
22
Q

How is staphylokinase a virulent factor of S. aureus?

A

L17

  • breaks down blood clots
  • allows rapid spread through damaged tissue
23
Q

How do lipases contribute to the virulence of S. aureus?

A

L17

  • break down lipases
  • allows growth in sebum
  • in sebaceous glands, hair follicles
24
Q

How does beta-lactamase contribute to the virulence of S. aureus?

A

L17

  • destroys beta-lactam antibiotics
  • penicillin
25
Q

How does polysaccharide slime layer (capsule) contribute to the virulence of S. aureus?

A

L17

  • prevents phagocytosis
  • enables attachment to medical devices (shunts, catheters)
26
Q

How does protein A contribute to the virulence of S. aureus?

A

L17

  • binds to antibody stems
  • prevents phagocytosis
  • inhibits complement activation
27
Q

How does cytolytic toxin contribute to the virulence of S. aureus?

A

L17

  • disrupts cell membranes
  • allows spread
28
Q

How does leukocidin contribute to the virulence of S. aureus?

A

L17

- kills leukocytes (WBC)

29
Q

How does exfoliative toxin contribute to the virulence of S. aureus?

A

L17

  • breaks down desmosomes (cell-cell contacts)
  • allows dissemination (spread)
30
Q

How does Toxic Shock Syndrome toxin contribute to the virulence of S. aureus?

A

L17

  • is a super antigen
  • triggers fever, vomiting, rash, shock
  • usually fatal

262A Oral Biology (4 decks)

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