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Yr 2 - Clinical Pathology > Vascular Infections > Flashcards

Vascular Infections Flashcards

1
Q

What is a vascular infection?

A

Infection where the source of infection in the heart of vascular system

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2
Q

What is the most important infection test for diagnosing invasive infection?

A

Blood cultures

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3
Q

What is bacteraemia?

A

Not a diagnosis, just means bacteria has been detected in the blood

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4
Q

What 2 components are required for the diagnosis of a bloodstream infection?

A

Bacteraemia + symptoms/signs of infection

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5
Q

Bacteraemia can be defined by the timing of bacteria presence in the blood. What are the 3 types?

A
  1. Transient
  2. Intermittent
  3. Continuous
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6
Q

What is transient bacteraemia?

A

Typically in bloodstream for minutes/hours before being cleared, often harmless and asymptomatic

(shown by peak 1)

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7
Q

What is intermittent bacteraemia? What type of infections can it be seen in?

A

Bacteria appear in bloodstream, are cleared and then appear again e.g. pneumonia, pyelonephritis, abscess, meningitis

Shown by peak 2

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8
Q

What is continuous bacteraemia? What type of infections can it be seen in?

A

Bacteria is detected every time blood cultures are taken e.g. endocarditis, mycotic aneurysm, pacing lead infection, infected DVT

Shown by line 3

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9
Q

Why should you not wait to sample blood until temp >38 degrees?

A

As this may not be the point where there is a peak in the number of bacteria in the blood - look for other symptoms e.g. confusion, tachycardia, haemodynamic instability, cold & shivery

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10
Q

What is a high temperature usually caused by?

A

High temperature is often due to the inflammatory response that occurs as a result of many organisms

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11
Q

What should you do (if you have time) before giving IV antibiotics in a patient presenting with an infection?

A

Take blood cultures

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12
Q

What is a CRBSI?

A

Intravascular Catheter-Related Bloodstream Infection

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13
Q

What are the 4 main routes of colonisation in a CRBSI?

A
  1. At time of insertion; ‘exit site’
  2. Via hub contamination (infection migrates down the lumen of the line)
  3. Haematogenous (bacterial and fungi get into blood stream via other source)
  4. Via infusion
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14
Q

Which bacteria is the most common cause of CRBSI?

A

Coagulase negative staphylococci 31%

  • Normally live on skin harmlessly, most common type
  • Skin breach can lead to infection
  • Can be due to bad handwashing
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15
Q

4 most common organisms causing CRBSI?

A
  1. Coagulase negative staphylococci 31%
  2. Staphylococcus aureus 20%
  3. Coliforms 13% e.g. E. coli
  4. Candida 9%
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16
Q

A patient presenting with which 3 features should be considered for CRBSI?

A
  1. Intravascular catheter
  2. Systemic signs of infection e.g. fever, confusion
  3. Bacteraemia or fungaemia
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17
Q

What is an indirect way of diagnosing CRBSI?

A

Clinical signs of infection that resolve on catheter removal

18
Q

What would the same organism detected in at least 1 peripheral blood culture AND the catheter tip indicate?

A

CRBSI

19
Q

What is differential time to positivity (DTP)? How can it be used to diagnose CRBSI?

A
  • DTP is the time between the through line sample becoming positive and peripheral sample becoming positive
    • 1) take peripheral culture from peripheral vein
    • 2) take blood culture from line
  • If DTP >2 hours (i.e. if through line culture becomes positive >2 hours before peripheral culture) then this is highly suggestive of CRBSI
20
Q

What is infective endocarditis?

A

Infection of the endocardium or devices within the heart

21
Q

What is the pathological lesion in infective endocarditis?

A

Vegetation;

  • Infection of the endocardium or devices within the heart
  • Wrapped in fibrin, attached usually to heart valve
22
Q

What type of bacteraemia (based on timing) is infective endocarditis? How would blood cultures demonstrate this?

A

Every blood sample should be positive for bacteraemia as this is chronic/continuous

23
Q

What are the 3 major types of presentation of infective endocarditis?

A
  • 1) Non-specific illness (lethargy, malaise, night sweats, anorexia, weight loss)
  • 2) Heart failure (SOB, orthopnea, PND)
  • 3) Results of extra-cardiac foci of infection (back pain from HVO, stroke, abdominal pain from splenic infarct
24
Q

When should you be highly suspicious of infective endocarditis?

A

Particularly if known heart valve disease, pacemaker, prosthetic valve, congenital heart disease

25
Q

What 8 clinical signs can be indicative of infective endocarditis?

A
  1. Fever >38
  2. Spinter haemorrhages
  3. Oslers nodes
  4. Janeway lesions
  5. Roth spots
  6. Conjunctival haemorrhages
  7. Splenomegaly
  8. New murmur
26
Q

Which bacteria are the 3 most common causes of infective endocarditis?

A
  1. Staphylococci (including coagulase negative staphylococcus & staphylococcus aures)
  2. Streptococci (mainly oral streptococci)
  3. Enterococci etc
27
Q

What is blood culture-negative infective endocarditis?

A

Blood culture-negative infective endocarditis refers to endocarditis without aetiology after three blood samples inoculated on standard media

28
Q

How must blood cultures be taken to diagnose infective endocarditis? What is the only exception to this?

A

Blood cultures: 3 spaced out over time (or 2 in severe sepsis)

29
Q

What imaging is used to diagnose infective endocarditis?

A

Echocardiography (transthoracic and transoesophageal)

30
Q

What are the risk factors for infective endocarditis?

A
  • Heart valve disease
  • Pacemaker
  • Prosthetic valve
  • Congenital heart disease
31
Q

What is the antimicrobial management for infective endocarditis?

A
  • Antimicrobial therapy: ideally directed towards pathogens identified by blood cultures
  • 4-6 weeks treatment usually IV but some evidence for oral switch
  • Example: flucloxacillin 2g 6-hourly IV for S. aureus (methicillin susceptible)
32
Q

When would surgery be needed in infective endocarditis?

A
  • Replace/repair damaged heart valves
  • Remove infection when antimicrobials don’t work
  • Removed infected devices e.g. pacemaker
  • Prevent complications like stroke
  • Drain purulent collections e.g. in spleen or spine
33
Q

What is a mycotic aneurysm?

A

Aneurysms resulting from, or secondarily infected by, microorganisms

34
Q

What are 4 different pathogeneses of mycotic aneurysm?

A
  • 1) Haematogenous seeding (e.g. secondary to infective endocarditis)
  • 2) Trauma to arterial wall + direct contamination (e.g. IVDU)
  • 3) Extension from a contiguous infected focus
  • 4) Secondary to septic microemboli (e.g. secondary to infective endocarditis)
35
Q

How can mycotic aneurysm present?

A
  • Presentation; usually systemic symptoms of infection and variable symptoms from aneurysm depending on location:
    • 1) No localising symptoms e.g. malaise, fever, anorexia
    • 2) Painless swelling
    • 3) Painful swelling
    • 4) Symptoms caused by rupture (e.g. intracerebral haemorrhage, collapse)
36
Q

What are the 5 bacteria that most commonly cause mycotic aneurysm?

A
  1. Salmonella spp.
  2. Staphylococcus aureus
  3. Streptococcus spp.
  4. Pseudomonas aeruginosa
  5. Escherichia coli
37
Q

How is mycotic aneurysm diagnosed?

A

Imaging (e.g. USS) and detection of bacteria within tissue

38
Q

How can a DVT become infected?

A
  • Seeded with bacteria during bacteraemia
  • Direct: IVDU injecting into femoral vein, seeds femoral DVT
39
Q

Which bacteria are the most common causes of an infected DVT?

A

Depends on mechanism but commonly S aureus, streptococci and anaerobes in IVDU

40
Q

How can an infected DVT present? Why can it sometimes present with respiratory symptoms?

A
  • Symptoms and signs of DVT
  • Systemic infection
  • Respiratory symptom
    • E.g. infected thrombus breaks from DVT travels via the venous system to the lungs – can lead to infected PE)
41
Q

Diagnosis of infected DVT?

A
  • Multiple (3) blood cultures
  • Confirmation of DVT plus exclusion of other causes e.g. IE
42
Q

Management of infected DVT?

A

Antibiotics AND anticoagulation

Yr 2 - Clinical Pathology (80 decks)

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