Microbiology - Infective Endocarditis

Question 1

What is infective endocarditis and how is it caused?

Answer 1

An infection of the innermost layer of the heart (usually the valves) - the endocardium

• Bacteria form vegetations on the valves, parts can fly off and travel round body causing various immune + embolic phenomena

Question 2

Which valves are involved in infective endocarditis?

Answer 2

• Mitral + aortic valves
• Tricuspid (R. sided) common in IVDU

Question 3

What are some RFs for Infective endocarditis?

Answer 3

• Bacteraemia: Long term lines, IVDU, poor dentition
• Abnormal valves: prosthetic valve, rheumatic heart disease
• Immunosuppression

Question 4

What is the difference between acute and subacute endocarditis?

Answer 4

Acute:
- Fulminant illness
- Pt very unwell: sepsis, rapid onset

Subacute:
- Weeks/months
- pt less unwell, more signs on examination

Question 5

What is a risk of prosthetic endocarditis?

Answer 5

Valve replacement

Question 6

What is non-infectious endocarditis and its causes?

Answer 6

Vegetations without infection

• SLE/APLS

Question 7

What are some causative pathogens of acute endocarditis?

Answer 7

High-virulence bacteria
- Strep. pyogenes (Group A Strep - Most common worldwide)
- Staphylococcus. aureus (Most common UK)
- CoNS - coagulase-negative staphylococci (most common in prosthetic valve)

Question 8

What are some causative pathogens of subacute endocarditis?

Answer 8

Low-virulence bacteria
- Staphylococcus epidermis
- Strep viridans
- HACEK (Haemophilus, Acinetobacter, Cardiobacterium, Eikinella, Kingella)

Question 9

What are some signs + symptoms of Infective endocarditis?

Answer 9

• Fever (PUO)
• Non-specific: anoresxia, weight loss, malaise, fatigue, night sweats, SOB
• New heart murmur (changes daily, regurgitant)

Question 10

What are some signs and symptoms characteristic of subacute infective endocarditis?

Answer 10

• Embolic phenomena: Janeway lesions, splinter haemorrhages, splenomegaly, septic abscesses, microemboli
• Immune phenomena: Roth spots, Osler’s nodes, haematuria (glomerulonephritis)

Question 11

What are the differences between Janeway lesions and Osler’s nodes?

Answer 11

Janeway lesions:
- Palms
- Painless
- Embolic phenomena

Osler’s nodes:
- Fingers
- Painful
- Immune phenomena

Question 12

What are some investigations for infective endocarditis?

Answer 12

• Blood cultures: >3 different sites, before Abx
• Echo

Question 13

What is the Duke’s criteria for diagnosis of Infective endocarditis?

Answer 13

Dx: 2 Major OR 1 Major + 1 Minor OR 5 Minor

Major:
- +ve blood culture growing typical organisms (>2x cultures >12hrs apart)
- New regurgitant murmur or evidence of vegetations on echo

Minor:
- RFs
- Fever >38C
- Embolic phenomena
- Immune phenomena
- +ve blood cultures not meeting major criteria

Question 14

What is the treatment for infective endocarditis?

Answer 14

IV Abx for ~6wks
- Start empirically, then change depending on culture results
- Acute: Flucloxacillin
- Subacute: Benzylpenicillin + gentamicin
- Prosthetic valve: vancomycin + gentamicin + rifampicin
- ?Surgical debridement

Question 15

What are the indications for surgical debridement of Infective endocarditis?

Answer 15

• Worsens on Abx
• Acute HF
• Aortic root abscess (prolonged PR on ECG)
• Prosthetic valve disease