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Endocarditis Flashcards

1
Q

What is Infective Endocarditis

A

A destructive process that affects mostly valves, leads to CHF, embolization and death if untreated

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2
Q

How to diagnose Endocarditis

A

Blood Tests 95% of cases

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3
Q

What are the causes of Endocarditis

A

Bacterial - Staphylococcus aureus and Streptococcus viridans cause > 80%, Yeast or Fungal infections

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4
Q

Where does Endocarditis occur?

A

Mostly valves, also paps or endocardial surface of ventricles, catheters, pacemaker wires, prosthetic materials

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5
Q

What is the classic presentation of Endocarditis?

A

Vegetations usually on the low pressure side of the valve(flow side) which is the atrial side for MV/TV and ventricle for PV/AOV

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6
Q

What does Endocarditis look like?

A

Shaggy smudgy, pedunculated, usually highly mobile and can seed other areas. Vegetations vary widely in appearance

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7
Q

what are the consequences of bacteria forming a plaque in heart valve?

A

Heart failure
Septicaemia with possible septic shock
Blood vessel blockage – tissue death

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8
Q

how does this happen?

A

Cant open properly
Can cause blockage
results in tissue death

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9
Q

what can predispose you to endocarditis?

A

Damaged heart valves
Replacement heart valves
Intravenous drug abuse
Long term venous access
Eg cancer patients, ICU patients

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10
Q

Subacute Endocarditis

A

Subtle presentation- Usually by streptococcus viridans carrying a low grade fever, fatigue, weight loss, cough, weakness, patient may not recognize seriousness of it

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11
Q

Acute Endocarditis

A

Usually staphylococcus aureus, carrying a high fever, rapid onset of symptoms like heart murmurs and can lead to CHF symptoms

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12
Q

Acute Endocarditis continued

A

Embolization signs with left heart involvement- petechiae and purpuric skin lesions and Janeway lesions, TIA, CVA

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13
Q

Purpuric skin lesions and petechiae

A

clumps on legs

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14
Q

Janeway lesions

A

on palms and soles of the feet

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15
Q

How to diagnose Endocarditis?

A

FUO, + new murmurs+ blood cultures

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16
Q

Blood cultures not always accurate for endocarditis

A

multiple samples needed, antibiotics for 2+ days affects results and fungal etiologies often have negative cultures

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17
Q

What size veg can echo detect?

A

> 3mm

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18
Q

What size veg can TEE detect?

A

> 1mm

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19
Q

If no veg does that mean no endocarditis?

A

No, must follow DUKE criteria

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20
Q

what are the major indicators of endocarditis

on criteria of DUKE?

A

Multiple positive blood cultures
- Typically 3 sets over 24 hours
Positive for typical endocarditis
- associated organism
Positive echocardiogram
- Visualisation of obstructing mass

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21
Q

what are the minor indicators of endocarditis?

A

Temperature above 38C
Predisposing heart condition
Immunologic phenomena
glomerulonephritis
Vascular phenomena
emboli
Positive blood culture – not fitting with major
Positive echo – not fitting with major

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22
Q

diagnosis based on DUKE criteria

A

2 major criteria
1 major and 3 minor criteria
5 minor criteria

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23
Q

Complications of endocarditis

A

Valvular regurgitation that worsens as lesion enlarges, valvular destruction, CHF from severe or acute regurg

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24
Q

Perivalvular abscesses (MV/AOV ring)

A

extensions of active infective disease, echolucent or echodense areas adjacent to valve apparatus, fistula formation, evaluate with color and doppler carefully, TEE

25
Perivalvular abscesses - what can happen
Emobization -TIA, CVA, LV wma- pulmonary embolus, pericarditis and pericardial effusion can result, mycotic aneurysm can occur- echolucent but hard to tell from abscess
26
Can Mechanical and tissue valves be affected by Infective endocarditis?
Yes - shadows and artifacts may impair visualization and perivalvular leaks or dehiscence may cause a rocking motion of the sewing ring
27
which organism causes 40% of endocarditis?
Viridans streptococci
28
where is it normally found?
a oral flora
29
how can infection start?
from brushing teeth with cut up mouth
30
which organism causes another 15% of infections?
Enterococci
31
where is it normally found?
gut
32
which organism causes 30% of infections?
Staphylococcus aureus
33
which group of people if Staphylococcus aureus infections much higher?
iv drug users
34
which group of organisms cause 10% of infections?
HACEK group - Haemophilus aphrophilus Actinobacillus actinomycetemcomitans Cardiobacterium hominis Eikenella corrodens Kingella kingeae
35
where are HACEK group found?
oral flora
36
pathogenesis of endocarditis?
Damaged or inflammed valve Organism binds to exposed antigens Eg fibronectin Immune response with fibrin deposition Binding of organism to fibrin antigens
37
how does the infection progress?
the cycle repeats Formation of growth - “vegetation” Disrupts valve function May shed infective fragments
38
in diagnosis, how is blood drawn for culture?
Clean skin site with alcohol - based wipe (make sure alcohol evaporates) Draw 5 – 10mls venous blood
39
how is the blood then processed?
Change needle on syringe Inject blood into culture vial Contains liquid culture media
40
what does culture vial base include to aid diagnosis?
fluorescent dye
41
how does the dye help?
Dye reacts with products of bacterial metabolism Fluorescent spectrum of dye changes with such reactions
42
how is this processed?
Automated system detects spectrum shift Automated system sounds alarm to indicate possible positive culture
43
what is done if a culture vial is flagged as positive?
~ 1ml removed Gram stain
44
what happens once Gram stain report completed?
Clinical team notified - Presumptive diagnosis discussed - presumptive antibiotics discussed
45
what is done to confirm diagnosis more?
Subculture to solid media - Purity plate for subsequent identification
46
what is done to aid antibiotic prescribing?
Disc sensitivity testing
47
what media is used for the subculture when gram negative bacillus suspected?
GNB’s MacConkey and chocolate at 37C in 5% CO2 Blood agar at 37C anaerobic Neomycin Blood agar 37C anarobic
48
gram negative cocci?
GNC’s chocolate at 37C in 5% CO2 Blood agar at 37C anaerobic
49
clumped cells?
GPC's Chocolate at 37C in 5% CO2 Blood agar at 37C anaerobic DNA’ase plate Plasma solution
50
chains?
GPC and GPB Blood and MacConkey at 37C in 5% CO2 Blood agar at 37C anaerobic
51
what must be passed onto clinical team?
With final identification With actual sensitivity profile Allows modification of initial therapy if needed
52
how long is Normal blood culture incubation?
5 days
53
why is it increased length of time in endocarditis?
increased to 10 days Fastidious and slow growing HACEK organisms
54
what is the standard therapy for Gram positive endocarditis?
a penicillin + gentamicin
55
what are the roles of each antibiotic?
Penicillin – breaks cell wall Gentamicin – attacks ribosome and prevent recovering from cell wall damage
56
what special requirements do Streptococci need in sensitivity testing?
Use “High dose” gentamicin disc Sensitive streptococci show synergy with penicillin and low dose gentamicin. Resistant streptococci: no synergy so gentamicin not used
57
why is Penicillin MIC testing a good idea?
Need an indication of degree of sensitivity Influences treatment duration
58
how long is treatment normally?
prolonged; months
59
how do you check on progress?
But testing blood regularly to insure enough antibiotic are in the blood to kill the specific organism infecting

medical microbiology (29 decks)

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