Endocarditis

Question 1

What is the definition of endocarditis?

Answer 1

Infection of the endocardium with formation of a vegetation resulting in damage to the cusps of valves

Question 2

What is quorum sensing?

Answer 2

Ability of an organism to produce chemical messengers to attract other bacteria

Question 3

What are some of the gram positive bacteria which cause endocarditis

Answer 3

• Gram positive rods,
• Staphylococci: Coagulase negative staphylococci or staph. aureus (methicillin resistant/sensitive)
• Streptococci: Strep viridans (oral flora) or enterococci

Question 4

What are the gram negative causes of endocarditis?

Answer 4

• Enterobacteriales (E.coli)
• Pseudomonas aeruginosa
• HACEK organisms
• Coxiella burnetii (Q fever)

Question 5

What fungi species can cause endocarditis

Answer 5

Candida species

Question 6

What are the different classifications of endocarditis?

Answer 6

• Native valve endocarditis (NVE)
• Endocarditis in IV drug users
• Prosthetic valve endocarditis

Question 7

What are the most common causative organisms for the different classes of endocarditis

Answer 7

• NVE: S. viridans
• IV drug users: S. aureus
• Prosthetic valve endocarditis: CoNS

Question 8

What are the risk factors for native valve endocarditis?

Answer 8

• Underlying valve abnormalities (aortic stenosis or mitral valve prolapse)
• Common causes for aortic stenosis is age related calcification, calcification of congenitally abnormal valve and rheumatic fever.

Question 9

Explain the pathogenesis of rheumatic fever

Answer 9

• Commonly caused by a streptococcus pyogens infections. The strep has M proteins which result in the formation of anti M antibodies. However M proteins are genetically similar to cardiac valves thus causing an autoimmune attack. This can result in a stenosis or regurgitation.

Question 10

What is the common valve affected in IVDU endocarditis and what are the different presentations?

Answer 10

• Tricuspid valve
• Acute: toxic presentation with progressive valve destruction and metastatic infection. Commonly caused by S.aureus.
• Subacut : Mild toxicity with presentation occuring over weeks to months. Rarely leads to metastatic infection. Commonly caused by strep.viridans or enterococcus

Question 11

What are the early manifestations of endocarditis?

Answer 11

• Incubation period of around 2 weeks
• Presents with fever and new murmur (think IE!) however murmur is absent in tricuspid endocarditis
• fatigue and malaise

Question 12

What are some of the embolic events in endocarditis

Answer 12

• Small emboli which can cause petechiae, splinter haemorrhages, haematuria.
• Large emboli which can cause a CVA or renal infarction
• Right sided endocarditis can cause a septic pulmonary emboli.

Question 13

What are some of the long term effects of endocarditis?

Answer 13

• Osler’s nodes which are painful palpable lesions found on the hands and feet.
• Immunological reactions which can cause splenomegaly. nephritis, vasculitis lesions of the skin and eye, clubbing.
  -Tissue damage which can cause valve destruction or valve abscess

Question 14

What should make you think infective endocarditis?

Answer 14

• ALL patietns with S.aureus bacteraemia
• IV drug users with ANY positive blood culture,
• All patients with prosthetic valves and positive blood culture

Question 15

How is the diagnosis of endocarditis made?

Answer 15

• 3 sets of blood cultures with 10mls/bottle, before antibiotics and with aseptic technique
• Echocardiogram (transoesophageal is more sensitive but more invasive)

Question 16

What is Duke criteria for endocarditis?

Answer 16

Two major criteria: Typical organism in 2 separate blood cultures. Positive echo or new valve regurgitation.
Five minor criteria: Predisposition, fever >38. Vascular phenomena (septic emboli), immunological phenomena (oslers nodes). Positive blood cultures which don’t meet major criteria.
Need 2 majors, 1 major and two minors or all 5 minors for a diagnoses

Question 17

What is the different managements for endocarditis

Answer 17

Medical - antimicrobial therapy using bactericidal agents.
Indications for surgery: Heart failure, uncontrollable infection (Abscess, persistent fever and pos blood cultures for> 7 days or infection caused by multi drug resistant organisms) or for the prevention of an emboli if they have large vegetations

Question 18

What is the antimicrobial therapy used for different organisms?

Answer 18

Streptococcus - Benzylpenicillin +/- gentamicin.
Enterococcus - Amoxicillin/vancomycin +/- gentamicin.
MSSA - Flucloxacillin +/- gentamicin.
MRSA - Vancomycin +/- gentamycin
CoNS - Vancomycin +/- Gentamycin +/- Rifampicin