Infective Endocarditis Flashcards Preview

Medical Microbiology Exam > Infective Endocarditis > Flashcards

Flashcards in Infective Endocarditis Deck (16)
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1
Q

What is infectious endocarditis?

A

Inflammation of the endocardium, usually to the inner valves, due to infection.

2
Q

What causes infective endocarditis?

A

Infection of the heart is caused by a variety of organisms
Infective endocarditis is initiated by microbial colonisation of natural or prosthetic heart valves, shunts and the septa
Most often bacteria – bacterial endocarditis

3
Q

How is infective endocarditis classified?

A

Classified in 2 ways:
Acute – presents with a high fever and high toxicity
- Death if untreated in few days or weeks
Sub-acute – presents with low grade fever, weight loss and night sweats
- Death in weeks to months

4
Q

Who is most at risk for infective endocarditis?

A

People with heart defects are at risk

Those with previous diseases:
Infective endocarditis, rheumatic heart disease

5
Q

What predisposing factors increase risk of infective endocarditis? (4)

A

Heart valve replacement
Intravenous drug use
Periodontal disease
Poor oral hygiene

6
Q

What organisms are most commonly associated with infective endocarditis? (6)

A
Streptococcus viridans (30-40%)
Enterococci (5-18%)
Other streptococci (15-25%)
Staphylococcus aureus (15-40%)
Coagulase-negative staphylococci (4-30%)
Gram negative bacilli (2-13%)
7
Q

What are the symptoms of infective endocarditis? (11)

A

Symptoms of endocarditis initially resemble influenza
- Febrile - fever never exceeds 39oC
- Chills
- Night sweats
- Anorexia
- Myalgia
- Arthralgia
Some patients experience neurological symptoms
- Strokes
- Intracerebral and subarachnoid haemorrhage
Peripheral symptoms include:
- Petechiae - conjunctiva (Roth spots), bucal mucosa and extremities
- Splinter and subungual haemorrhages
- Osler nodes on digits

8
Q

How does colonisation on the heart valves begin?

A
  • Turbulent flow mechanically damages the endothelium
  • Damage induces the deposition of platelets and fibrin
    - Induces further deposition
    - Eddies form that trap circulating bacteria
    - Bacteria bind to cause more damage – inflammation and complement
    - Thrombotic mesh forms - Mature vegetation
9
Q

Why are patients with abnormal valves at higher risk for infective endocarditis?

A

Abnormal valves are prone to damage

  • Turbulent flow mechanically damages the endothelium
  • Fibrin and platelets are deposited
  • Fibrin deposits colonised by bacteria
  • Bacteria are resistant to platelet antimicrobial peptides and persist
10
Q

How does mature vegetation contribute to the survival of bacterial pathogens?

A

Mature vegetation is a protective mechanism for the bacteria

  • It is an example of the biofilm mode of growth
  • Bacteria growing in a biological matrix on abiotic or biotic surfaces
  • Gives protection from immune system
  • Gives protection from antibiotics
11
Q

How do septic emboli form?

A

Increased turbulence can form septic emboli

  • Parts break off due to shear forces
  • May block blood vessels leading to stroke or allow abscess formation
12
Q

How does host immunity contribute to damage?

A

Inflammatory responses

  • IL – 1 may have a role in causing increased fibroblast proliferation and profibrotic factors
  • Deposition rate increased

Complement

  • Responds to immune complexes formed in response to bacterial cells
  • Complexes cause glomerulonephritis – physical blockage
  • Complement causes arthritis and cutaneous squelae
  • Splinter haemorrhages, Osler nodes, Janeway lesions
13
Q

What complications can occur from infective endocarditis?

A
Heart failure or severe damage
 - Congestive heart failure
 - Ruptured chordae tendineae
 - Perforation of valves
Complications depend on side affected
 - Left - coronary emboli
 - Right - lung complications
14
Q

How is infective endocarditis treated?

A

Highly aggressive therapy is required due to the protective effects of the mature vegetation

  • High concentrations must be given
  • Balance toxicity and efficacy
  • Treatment is over long periods
  • Surgery may be necessary
  • Removal and replacement of heart valves is common
15
Q

What treatment would be given for infectious endocarditis due to E. faecium?

A

IV Ampicillin 2g every 4 hours
IV Gentamicin 80mg twice daily

Both given over a course of 4 weeks, however 6 weeks of combination therapy is recommended in patients who had symptoms that persisted for at least 3 months before beginning therapy

16
Q

How is infective endocarditis diagnosed?

A

3 sets of blood cultures of 1 hour or longer

Echocardiography if enterococcal endocarditis is suggested.