L25, L27- CVS Infections I, II Flashcards
endocarditis will mostly affect (1) valves; it will often specifically affect (2) valve in (3) patients
1- mitral, aortic
2- tricupid
3- IV drug users
briefly describe the pathogenesis of endocarditis
1) initial damage via mechanical and endothelial injury
2) platelet and fibrin thrombus
3) bacteremia (via some exposure or route of administration)
4) bacterial adhesin
5) biofilm formation (vegetation)
what is a NBTE
nonbacterial thrombotic endocarditis due to inflammation and or microscopic thrombi after some sort of initial damage (mechanical or endothelial injury)
vegetation in endocarditis will often occur at (1) point of the heart because of (2)
low pressure side of valve (atrial side): mitral valve prolapse or something else will cause turbulent blood flow and stasis in atrium allowing vegetation (and or coagulation / thrombus to form)
what are the 3 features of endocarditis that must be considered
1) Etiological Agent: bacteria, fungi
2) Valve Type: native valve (72%) or prosthetic valve (21%- either early/days-wks or late/mos-yrs after surgery)
3) community vs nosocomial (antibiotic resistant, opportunistic) acquired infection
Endocarditis is more likely to occur in (men/women) of the (2) age group.
- (3) cardiac risk factors
- (4) non-cardiac risk factors
1/2- men, >65 y/o
3- previous IE hx, prosthetic valve, cardiac device, congenital / valvular heart disease
4- IV drug use or IV line, immunosuppression (drugs or disease), recent dental or surgical procedure, hemodialysis
the risk factors of endocarditis are related to (1) or (2)
1- direct damage to endothelium
2- introduction of microorganism into blood
IE is diagnosed based on (1), which includes (2), (3), (4)
(infective endocarditis) Duke criteria: -clinical presentation: sxs, risk factors -microbiology: blood cultures -imaging: echocardiogram
List the clinical features of IE (indicate the 2 most common features)
(infective endocarditis)
-fever (80%), heart murmur (85%)
- embolic phenomenon (>50%), petechiae (20-40%), skin manifestations (18-50%), splenomegaly (20-57%)
- Uncommon: osler’s nodes (painful red lesions on hands/feet), janeway lesions (nonpainful nodules of soles/palms), roth spots (white on retina)
describe taking blood cultures in suspected infective endocarditis (IE)
- 2 bottle (aerobic and anaerobic) sets from 3 different locations (=> 96-98% detection)
- note: bacteremia is usually continuous and best to take sample prior to antibiotics
-10% of cases have no growth (blood culture negative endocarditis)
(1) is the first imaging completed in suspected IE
(2) will be complete subsequently if (1) is positive for IE or IE is still suspected
1- transthoracic echocardiogram
2- transesophageal echocardiogram
list the major criteria for IE in Duke Criteria
1) Positive Blood Culture: from 2/3 of samples for most organisms, 3/3 of any organism, or 1/3 for coxiella burnetti
2) evidence of endocardial involvement: echocardiogram shows oscillating intracardic mass on valve, abscess, partial dihiscence of prosthetic valve, or new valvular regurgitation
list the minor criteria for IE in Duke Criteria
- Risk factors: predisposing cardiac condition, IV drug use
- Temp. > 38C, 100.4F
- vascular phenomenon
- immunological phenomenon
- microbiological evident (incomplete blood culture evidence for major parameters otr something else)
- echocardiogram findings not meeting major criteria
Describe Duke Criteria in terms of diagnosing
Definite IE (major - minor): 2 - 0, 1 - 3, 0 - 5
Possible IE: 1 - 1, 0 - 3
Rejected: alternate Dx, resolution <4days with antibiotics, criteria not met
80% of cases of IE are caused by…..
- Staph spp.
- Strep spp.
list the medically relevant Staph. spp. for IE and include the biological features
All: gram+, catalase+, ‘grapelike’ clusters, comensal flora of skin / mucous membranes
Coagulase+: S. aureus
CoNA: S. epidermidis, S. lugdunensis, S. saprophyticus
S. aureus is one of the most common causes of endocarditis in (native/prosthetic) valves. It is a fairly (aggressive/benign) disease and increases the risk for (3).
1- both valve types
2- aggressive
3- embolism, stroke, persistent bacteremia, death
S. aureus bacteria that cause endocarditis usually (do/do not) have polysaccharide capsules. The main surface adhesin is (2) and the critical toxin is (3). The last important virulence factor of S. aureus that is critical to vegetation is (4).
1- do have capsules (90%)
2- Clumping factor A (ClfA)- fibrinogen binding protein
3- α-toxin / α-hemolysin
4- biofilm formation (colonization in layers thru polymer attachment)
The major endocarditis causing CoNS is (1), usually in a (2) setting with (3) patients.
(1) is usually found on (4), therefore introduction into blood is commonly through (5) [note- also a factor for (2)].
1- S. epidermidis
2- hospital-setting (33% of all PVE)
3- prothetic valve patients (major cause of PVE)
4- human skin
5- medical device insertion (via patients or healthcare worker’s skin)
briefly describe the pathogenesis of S. epidermidis causing endocarditis
1) found on skin (patient or healthcare worker) –> picked up by anything inserted / passing through external barrier)
2) rapidly attaches to biomaterial => biofilm
3) inc immunosuppressed and compromised populations and inc use of bioprosthetic devices
(1) is the second most common CoNS causing endocarditis. It is not as frequent as other IEs, but it is usually more (2) and most cases require (3).
1- S. lugdunensis
2- aggressive (>50% => destructive IE)
3- surgery
S. lugdunensis is mostly found on (1). (2) and (3) are its important virulence factors. (4) and (5) are its critical agar / culture distinguishing features.
1- skin, inguinal region
2- adhesion factor (ClfA) binds fibrinogen
3- biofilm formation
4- non-mannitol fermenter
5- β-hemolysis (blood agar, complete hemolysis)
describe how to differentiate S. aureus and S. epidermidis
1) Coagulase Test: + = aureus / - = epidermidis
2) Mannitol agar:
- Selective: 7.5% NaCl only allows Staph. spp. to grow
- Differential: only S. aureus ferments mannitol (+, red –> yellow), S. epidermidis remains red (-)
(1)% of nosocomial S. aureus strains of methicillin resistance and (2)% S. epidemidis are resistant.
1- 40-60% (aureus)
2- 75-90% (epidermidis)
