endocarditis Flashcards
what is transient and continuous bacteremia?
- Transient bacteremia
Common
Usually asymptomatic
Triggered by daily activities - flossing, tooth brushing, chewing hard candy, medical procedures et.c - Continuous bacteremia
Bacteremia lasting longer than 30 minutes duration
In Endocarditis, bacteremia persists over long periods – until sterilization of the vegetations due to continuous release of bacteria from vegetations
What is the classification of endocarditis based on?
Older classification based on presentation
Acuity related to organism
Acute - S. aureus, Strep pneumoniae, GAS
Subacute - viridans group strep
Currently classification is more commonly based on risk factors Nosocomial – often line associated Native valve Prosthetic valve Injection drug use associated
what is the pathogenesis of endocarditis?
transient bacteremia + turbulent flow across a valve –> bacterial adherence and colonization –> local tissue damage, platelet adherence, fibrin deposition –> vegetation this can lead to one of two things. Release of bacteria from vegetation –> circulating immune complexes –> golmerulonephritis, positive rheumatoid factor, vasculitis, osler’s nodes/roth spots OR release of tissue from vegetation –> emboli –> stroke, septic pulmonary emboli, splinter hemorrhages, metastatic abscesses, janeway lesions
what is bacterial pathogenesis for endocarditis?
- Serum resistance (complement resistance) – allows for persistence of viable bacteria in blood.
Gram positives > gram negatives - Bacterial adhesins – promote binding to endothelial cells and nonbacterial thrombus (nonbacterial thrombus forms on damaged valve surfaces)
- Invasiveness
Elaboration of extracellular proteases
Metastatic seeding
What is a roth spot?
1 – Roth spots are ring shaped retinal hemorrhages with a white center of coagulated fibrin.
Immune complex mediated vasculitis.
May also be found in HIV retinopathy, diabetes, leukemia
what are janeway lesions?
Janeway lesions are irregular, nontender hemorrhagic macules located on the palms, soles, thenar and hypothenar eminences of the hands, and plantar surfaces of the toes. They typically last for days to weeks. They are usually seen with the acute form of bacterial endocarditis.
The lesions are believed to be caused by septic microemboli from the valvular lesion. Cultures of specimen are usually positive. Histologically, Janeway lesions consist of microabscesses in the dermis with thrombosis of small vessels without vasculitis.
How do Janeway lesions and Osler’s nodes differ?
Pathogenesis- Pathogenesis, one is embolic and the other is related to immune complex
Presence or absence of tenderness
Janeway - Painless, hemorrhagic lesions
Embolic in origin
Typical locations: palms and soles
Osler’s nodes - Painful
Immune complex mediated - ?
Typical locations: finger pulp, thenar eminence
what lab features might be present in endocarditis?
anemia - usually normochromic normocytic
thrombocytopenia
hematuria
increased ESC/CRP
Indicators of immune activiation - increased rheumatoid factor, cryoglobulins, hypergammaglobulinemia, circulating immune complexes, decreased complement levels
what do you need for blood culture?
When you order a blood culture…you get:
Two bottles from one site (aerobic and anaerobic) PLUS one aerobic bottle from a second site.
Why the second site?
do help detect any contamination upon retrieval of specimen
Does this allow you to make a diagnosis of endocarditis?
No, because you need to test over time to prove it is a continual bacteremia.
What do you need to guide antibiotic choices in the blood culture? and what do you need to do in terms of documentation?
The organism – to guide antibiotic choices
A single blood culture will yield this information
Documentation of continuous bacteremia – to make diagnosis and guide duration of therapy
Requires multiple cultures over time
How can we get the information we need to make an accurate Dx?
Order one “set” of blood cultures = 3 bottles PLUS one aerobic bottle x 2 at specified times
If patient is unstable, use short intervals for multiple draws – 45-60 minutes
If patient is stable and no need to initiate antibiotics immediately, can use longer intervals such as 12 hours
Anaerobic endocarditis is rare – no need for anaerobic bottle
We are looking for a specific species to be present continuously so do not need extra vial to rule out contamination
what if someone has already started antibiotics, will this effect the blood tests?
Because it takes time for vegetations to be sterilized, we can often recover organisms even after initiation of antibiotics.
Simple Staph bacteremia should clear within 2-3 days
Staph endocarditis bacteremia typically persists 5+ days
Draw more cultures
Towards the end of the dosing interval
Use ‘resin’ bottles to enhance growth
Does he need an echo to diagnose endocarditis?
Blood cultures are positive for Staphylococcus aureus in all vials and 3 out of 3 sets taken over 4 hours.
he doesn’t need this.
what’s the role of echocardiography?
- To help confirm a clinical suspicion of endocarditis when blood cultures:
When blood cultures are negative but suspicion is high
Blood cultures not obtained early enough
Fastidious pathogens - “culture negative” endocarditis
- To assess for complications and need for surgery Size of vegetation Location of vegetations – which valve? Paravalvular abscesses Leaflet damage CHF
What is the most common bacterial cause of native valve endocarditis?
viridians group streptococcus
which organism is the most common cause of prostheticvalve endocarditis?
coagulase negative staph
