Lecture 21: Infective endocarditis

Question 1

What are indications for endocarditis?

Answer 1

• Symptoms and signs of infection
• Embolic phenomena
• Abnormal heart valve

= Endocarditis

Question 2

What are the signs and symptoms of endocarditis?

Answer 2

• Fever
• Splinter haemorrhages
• Early diastolic murmur

Question 3

Describe endocarditis pathogenesis:

Answer 3

Turbulent flow through abnormal valve, due to congenital abnormality, nodules from rheumatic heart disease
->
Platelets and fibrin attach to damaged valvular epithelium forming sterile vegetations
->
Transient bacteraemia arising from mouth, skin, gut, urinary tract, etc, seeds bacteria onto sterile vegetations
->
Infected vegetation enlarges and sheds infected emboli and leads to valvular destruction

Question 4

Describe the flow diagram of endocarditis

Answer 4

Insert slide 9

Question 5

Whats the diagnosis methods of endocarditis?

Answer 5

• > Continuous bacteraemia (on 3 blood cultures 20 mins apart) or culture excised valve)
• > High concentration of bacteria in and on vegetation, with bacteria continually shed from vegetation into blood

= Organism identified in about 95% cases

Question 6

What are the three types of bacteraemia?

Answer 6

True, contaminant, transient

Question 7

What is true bacteraemia?

Answer 7

• Pathogen cultured
• Sometimes more than one set of blood cultures positive
• Clinically compatible infective source identifed

Question 8

What is contaminant bacteraemia?

Answer 8

• Skin commensal cultured
• Only one set of blood cultures positive
• no apparent infective source

Question 9

What is transient bacteraemia?

Answer 9

• Gut or mouth organism cultured
• Blood cultures only positive briefly
• No apparent infective source

Question 10

Whats the treatment of infective endocarditis?

Answer 10

• Infection of heart valves is never cured by host defenses - universally fatal without effective antibiotic treatment

Bactericidal antibiotic treatment for weeks

Question 11

What mainly causes endocarditis?

Answer 11

Viridans streptococci

Question 12

Once a microbial is identified what is the importance of antibiotic susceptibility testing?

Answer 12

Need to test the bacteria to determine minimum inhibitory concentration distribution to determine dosage of antibiotic

I.e minimum inhib concentration to kill viridans streptococci

Question 13

What is MIC of penicillin? - viridans streptococci

Answer 13

Most strains of viridans streptococci are inhibited by concentrations of penicillin that are readily achieved in serum with IV treatment

but, minority of strains of viridans streptococci are inhibited by slightly higher concentrations that cannot be readably achieved with IV treatment

Question 14

What is MIC of penicillin? - staphylococci aureus

Answer 14

Minority strains of staphylococcus aureusare inhibited by concentrations of penicillin that are readily achieved in serum with IV treatment

but, majority of strains of staphylococcus aureus are inhibited by slightly higher concentrations that cannot be readably achieved with IV treatment

Question 15

What is bacteriastatic vs bacteriacidal? Whats the consideration of vegetations and treatment?

Answer 15

Use a bactericidal drug or drug combination - because neutrophils have difficulty entering vegetations

Bacteristatic antibiotics: Erythromycin, doxycycline, etc (host defenses do the rest, no function in this case because of difficulty)

Bacteriacidal Antibiotic: I.e penicillin, cephalosporin

Question 16

What is the endocarditis treatment?

Answer 16

Antibiotic: Dependent on organism
Method: IV
Dose: Always high dose
Duration: Usually 2 weeks, often 4
Cure rate: 70-90%

Question 17

How is endocarditis prevented?

Answer 17

Reduced risk of bacteraemia in persons known to have abnormal heart valves

i.e antibiotic prophylaxis at time of dental work (lol this doesnt help)

Usually give only one dose of penicillin

Question 18

Describe rheumatic pathogenesis and note how this is different to infective endocarditis?

Answer 18

Pharyngitis due to strep. pyogenes -> Immune responses to GAS throat infection -> Inflammation of joints, heart valves, skin, brain

Question 19

How is rheumatic fever diagnosed?

Answer 19

Inflammation (not infection) of heart, joints, skin, brain

Fever

Raised ESR and CRP

S. pyogenes isolated from throat

Antibody responses to s. pyogenes

Question 20

Compare and contrast ARF and endocarditis:

Answer 20

ARF: S. pyogenes only -> immunological damage to valve

Endocarditis: Viridans streptococci + Others -> infects valves -> vegetations (pre-existing?)

Question 21

Insert slide 35

Answer 21

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