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Divine infection > Key Bacteria - Staphylococci > Flashcards

Key Bacteria - Staphylococci Flashcards

1
Q

Give 7 key characteristics for all Staphylococci bacteria?

A
  • Gram positive
  • Cocci
  • In clusters
  • non-motile
  • non-spore forming
  • Facultative anaerobic
  • Either coagulase positive or negative
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2
Q

What is the structure of Staphylococcus aureus?

A

Gram positive Cocci bacteria

In clusters

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3
Q

Where is Staph. aureus found?

A

Found on skin and mucous membranes

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4
Q

How is Staph. aureus spread?

A

Contagious spread, from person to person.

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5
Q

Examples of conditions commonly linked to Staph. aureus infection?

A
  • Sepsis
  • Pneumonia
  • Localised skin infections
  • Cellulitis
  • Endocarditis
  • Abscesses
  • Co-morbidities & immunosuppression
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6
Q

Staph. aureus virulence factors?

A
  • Capsule
  • Coagulase enzyme
  • Cytotoxic exotoxins
  • Protein A
  • Fibronectin-binding protein
  • Clumping factor
  • Superantigen exotoxins
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7
Q

Explain the Capsule, as a virulence factor of Staph. aureus?

A

Enables inc. resistance to phagocytosis

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8
Q

Explain Protein A as a virulence factor of Staph. aureus

A

Binds to Fc region of IgG antibodies, and acts as an anti-opsin.

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9
Q

Explain Fibronectin-binding protein as a virulence factor of Staph. aureus

A

Promotes binding to mucosal cells & tissue matrices

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10
Q

Explain Coagulase enzyme as a virulence factor of Staph. aureus?

A

Enzyme catalyses breakdown of fibrinogen to form clot

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11
Q

Explain Clumping factor as a virulence factor for Staph. aureus?

A

This FnBP (…) enhances clumping of the organism in the presence of plasma

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12
Q

Explain cytotoxic exotoxins as a virulence factor for Staph. aureus?

A

Exotoxins are toxic to, and attack mammalian cells. Cause lysis of cells.

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13
Q

Explain superantigen exotoxins as a virulence factor of Staph. aureus?

A

Affinity for T-cell receptor—MHC Class 2 Antigen complex.
The toxins stimulate an enhanced T lymphocyte response.
Causes toxic shock by release of large amounts of T-cell cytokines
(Potential link to DIC)

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14
Q

Investigations for Staph. aureus infection?

A
  • Full blood count = inc. WBC, neutrophils etc.
  • CRP (signifies inflammation)
  • blood culture — swab for gram stain
  • Coagulase test = positive result
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15
Q

Treatment for Staph. aureus infection?

A

Antibiotics

  • Flucloxacillin = inhibits formation of cross links in thick peptidoglycan cell wall (Staph. aureus = gram positive)
  • Amoxicillin = same effect
  • Amoxiclav = use when resistant to amoxicillin
  • Vancomycin = for MRSA
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16
Q

What is the structure of Staph. Epidermidis?

A

Gram positive, cocci bacteria

17
Q

Where is Staph. epidermidis found?

A

Present normally on skin and mucous membranes

18
Q

How is Staph. epidermidis infection spread?

A
  • Contagious spread person to person
  • Biofilm = allows it to spread from surface to person

Contraction - Key clinically relevant HAI
- on catheters, prosthetic devises & heart valves

19
Q

Examples of conditions commonly linked to Staph. epidermidis?

A
  • Skin infections
  • Sepsis
  • Prosthetic device & heart valve infections
  • Endocarditis (infection of the heart valves and parts of the inside lining of the heart muscle)
  • Catheter infections (catheter-induced UTIs)
20
Q

Staph. epidermidis virulence factors?

A
  • Biofilm production

- Capsule

21
Q

Explain Biofilm as a virulence factor of Staph. epidermidis?

A

Extracellular (glycocalyx) “slime” production that:

  • Acts as a glue adhering it to surfaces and cells
  • Also acts as a diffusion barrier to host defences and antibiotics, causes resistance to phagocytosis and some antibiotics (e.g. vancomycin)
22
Q

Investigations for Staph. epidermidis infections?

A
  • Full blood count
  • Blood cultures = gram +ve cocci (clusters)
  • CRP
  • Coagulase test = coagulase negative
23
Q

Treatments for Staph. Epidermidis?

A

Antibiotics
- vancomycin

  • or rifampin if vancomycin resistant

Divine infection (6 decks)

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