Staph Aureus Bacteraemias Flashcards

1
Q

Does Staph Aureus cause disease via a toxin mediated mechanism or non-toxin mediated mechanism?

A

Causes disease via both toxin mediated and non-toxin mediated mechanisms

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2
Q

Is staph aureus gram positive or gram negative? How does it appear on gram stain?

A
  • Gram positive

- Forms grape like clusters and appears purple in colour on gram staining

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3
Q

What percentage of people are persistently / transiently colonized by S. aureus? Who is most vulnerable to colonization?

A
  • 25-50% of people persistently / transiently colonized
  • Insulin dependent diabetes
  • HIV infection
  • Patients undergoing haemodialysis
  • Individuals with skin damage
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4
Q

Most common sites of S. aureus colonization?

A
  1. Nostrils (anterior nares)
  • Skin
  • Vagina
  • Axilla
  • Perineum
  • Oropharynx
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5
Q

How are S. aureus blood stream infections classified?

A
  1. Environment of acquisition:
    - Healthcare associated
    - Community acquired
  2. Absence or presence of associated infection sites
    - Primary
    - Secondary
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6
Q

What are some different ways S. aureus infection can manifest itself in the patient?

A
  • Skin & soft tissue infection
  • Localized pyogenic infections (carbuncle etc.)
  • Deep seated abscess (necrotizing fasciitis etc.)
  • Bone infection (osteomyelitis etc.)
  • Infective endocarditis
  • Pneumonia / empyema
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7
Q

What are the most frequent sites for S. aureus infection to metastasize to?

A
  • Bones and joints (esp. prosthetics)
  • Epidural space and intervertebral discs
  • Cardiac valves (native / prosthetic) & cardiac devices
  • Visceral abscesses in spleen, kidneys & lungs
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8
Q

What investigations can be used for suspected S. aureus infection?

A
  • Blood culture / microscopy (multiple)
  • Bone biopsy (if bone infection)
  • XRay, CT, MRI, radionucleotide screening
  • TOE: transthoracic echocardiography

(heavily dependent on manifestation of the infection)

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9
Q

Management of S. aureus infection?

A
  • Antibiotic therapy
  • Source identification & clearance
  • Surgical intervention where appropriate (abscess drain etc.)
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10
Q

List the different antibiotics that can be used to treat S. aureus infection

A
  • Flucloxacillin
  • Vancomycin
  • Teicoplanin
  • Linezolid
  • Daptomycin
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11
Q

What needs to be known about the S. aureus infection before antibiotic treatment can be planned?

A

whether it is MRSA or MSSA

  • MRSA will not respond to methicillin based antibiotics such as flucloxacillin
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12
Q

What is the first line antibiotic for MSSA? Describe the course of treatment

A
  • Flucloxacillin

- Minimum course of treatment is 14 days

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13
Q

What is the first line antibiotic for MRSA? What are some of the downsides to use of this antibiotic?

A
  • Vancomycin

- Has poorer tissue penetration (bone & lung manifestations) & may have inconvenient side effects

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14
Q

Which antibiotic has the best tissue penetration, making it useful for bone & lung manifestations of S. aureus infection? Downsides?

A
  • Linezolid

- Has harsh side effects such as peripheral neuropathy, toxicity etc.

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