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Y2 Clinical Pathology > Vascular Infections > Flashcards

Vascular Infections Flashcards

1
Q

What is meant by the term “vascular infection”?

A

There is a source of infection in the heart or vascular system

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2
Q

What is bacteraemia?

How is this different to a bloodstream infection?

A

Bacteraemia is NOT a diagnosis - it means that bacteria have been detected in the blood

blood cultures are an important infection test

bacteraemia + symptoms/signs of infection = bloodstream infection

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3
Q

What are the 3 different types of bacteraemia?

A

1. Transient

2. Intermittent

  • pneumonia, pyelonephritis, abscess, meningitis

3. Continuous

  • endocarditis, mycotic aneurysm, pacing lead infection, infected DVT
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4
Q

When should blood cultures be taken?

A

Blood cultures are taken when temperature reaches 38oC or above

don’t just sample blood when temp > 38oC, use other features such as confusion

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5
Q

What is the pathogenesis of an intravascular catheter-related bloodstream infection (CRBSI)?

A

The routes of colonisation and infection are:

  • at the time of insertion
  • via hub contamination
  • haematogenous
  • via infusion
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6
Q

What organisms are most commonly responsible for an intravascular catheter-related bloodstream infection (CRBSI)?

A
  • Coagulase negative staphylococci (31%)
  • staphylococcus aureus (20%)
  • candida (9%)
  • enterococci (9%)
  • coliforms (13%)
  • pseudomonas aeruginosa (4%)
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7
Q

How is CRBSI diagnosed?

A

Clinical diagnosis is unreliable

CRBSI should be considered in any patient with an intravascular catheter and

  1. Systemic signs of infection, or
  2. Bacteraemia or fungaemia
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8
Q

when CRBSI is suspected, what tests are used to diagnose it?

A
  • Clinical signs of infection that resolve on catheter removal
  • same organism from at least 1 peripheral blood culture and catheter tip OR
  • differential time to positivity (DTP)

paired peripheral and through line blood cultures (same volume, same time) should be sent from all lumens when CRBSI is suspected

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9
Q

What is differential time to positivity (DTP)?

How can it be used to detect CRBSI and what is the main limitation?

A

Same volume of blood from the lumen and peripheral vein is taken at the same time

growth of microbes from a blood sample drawn from a catheter at least 2 hours before microbial growth is detected int he blood sample from a peripheral vein

using DTP > 2 hours will fail to detect some CRBSIs, but a positive result has a high probability of being CRBSI

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10
Q

What reading for DTP is highly specific for CRBSI?

A

a DTP > 2 hours is highly specific for CRBSI

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11
Q
A
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12
Q

What is infective endocarditis?

A

An infection of the endocardium or devices within the heart

there are vegetations present which contain densely packed bacteria

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13
Q

What types of things should be looked for in a clinical history for infective endocarditis?

Which patients are at high risk?

A
  • Non-specific illness
    • lethargy, malaise, night sweats, anorexia, weight loss
  • heart failure
    • ​shortness of breath, orthopnea, PND
  • results of extra-cardiac foci of infection
    • ​back pain from HVO, stroke, abdominal pain from splenic infarct

particularly in patients with known heart valve disease, pacemaker, prosthetic valve or congenital heart disease

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14
Q

what is meant by “stigmata” when performing a clinical examination of a patient with infective endocarditis?

A

A physical mark that is characteristic of the disease

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15
Q

What are the clinical signs of infective endocarditis?

How common are they?

A
  • Fevers > 38oC (96%)
  • splinter haemorrhages (8%)
  • Oslers nodes (3%)
  • Janeway lesions (5%)
  • Roth spots (2%)
  • conjunctival haemorrhages (5%)
  • splenomegaly (11%)
  • new murmur (48%)
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16
Q

What is the aetiology of infective endocarditis like?

A
17
Q

What are Osler nodes?

A

Red-purple, slightly raised, tender lumps, often with a pale centre

pain often precedes the development of the visible lesion by up to 24 hours

18
Q

what are janeway lesions?

A

Non-tender, small erythematous or haemorrhagic macular, papular or nodular lesions on the palms or soles

they are only a few millimetres in diameter

19
Q

what are Roth spots?

A

White-centred retinal haemorrhages that are associated with multiple systemic illnesses

20
Q

How is infective endocarditis diagnosed?

A

Echocardiography (transthoracic and transoesophageal)

AND

blood cultures - 3 sets taken at different times

(2 sets in severe sepsis)

21
Q

What is involved in the antimicrobial management of infective endocarditis?

How long is treatment given for and what are the different treatments?

A

Antimicrobial therapy should be directed towards the pathogens identified by blood cultures

treatment for 4-6 weeks is usually IV, but some evidence for oral switch

usually treatment is fluclocoaxacillin 2g 6-hourly IV for S. Aureus (methicillin-susceptible)

22
Q

In addition to antimicrobials, what is involved in the non-antimicrobial management of infective endocarditis?

A

Surgery may be required to:

  • replace or repair damaged valves
  • remove infection when antimicrobials don’t work
  • remove infected devices e.g. pacemaker
  • prevent complications like stroke
  • drain purulent collections e.g. in spleen or spine
23
Q

What is a mycotic aneurysm?

A

Aneurysms resulting from, or secondarily infected by, microorganisms

24
Q

What is involved in the pathogenesis of mycotic aneurysm?

A
  • Haematogenous seeding (e.g. secondary to IE)
  • trauma to arterial wall + direct contamination (e.g. IVDU)
  • extension from a contiguous infected focus
  • secondary to septic microemboli (e.g. secondary to IE)
25
Q

What is the presentation of mycotic aneurysm like?

A

Usually systemic symptoms of infection and variable symptoms from aneurysm, depending on the location

  • no localising symptoms
  • painless swelling
  • painful swelling
  • symptoms caused by rupture (e.g. intracerebral haemorrhage, collapse)
26
Q

What organisms tend to cause mycotic aneurysm?

A
  • Salmonella spp
  • staphylococcus aureus
  • streptococcus spp
  • pseudomonas aeruginosa
  • escherichia coli
27
Q

What is involved in the diagnosis and management of mycotic aneurysm?

A

Diagnosis:

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

Management:

  • surgical removal
  • stenting or coiling (depending on location) with antibiotics
28
Q

What is an infected deep vein thrombosis?

A

DVTs can be seeded with bacteria during bacteraemia or directly

e.g. IVDU injecting into femoral vein, seeds femoral DVT

29
Q

What is the presentation of infected DVT like?

A
  • Symptoms/signs of DVT and systemic infection and/or respiratory symptoms
  • when infected thrombus breaks from DVT, it travels via the venous system to the lungs (infected pulmonary emboli)
30
Q

What typically causes an infected DVT?

A

It depends on the mechanism, but commonly:

  • S aureus
  • streptococci
  • anaerobes in IVDUs
31
Q

What is involved in the diagnosis and management of infected DVT?

A

Diagnosis:

  • multiple (3) blood cultures
  • confirmation of DVT plus exclusion of other causes

Management:

  • antibiotics plus anticoagulation
32
Q
A

Y2 Clinical Pathology (76 decks)

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