1. Usual subacute bacterial endocarditis (SBE) pathogens include:

a. S. viridans

b. Enterococci (E. faecalis, E. faecium)

c. E. coli

d. Legionella, Coxiella burnetii, Chlamydia psittaci, Brucella

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Answer: Viridans streptococci from the mouth is responsible for 50-70% of all cases of native valve endocarditis in normal hosts. Usual endocarditis pathogens following GI and GU procedures are enterococci. Pathogens causing culture-negative endocarditis, which require specific serology for diagnosis, include Legionella, Coxiella burnetii, Chlamydia psittaci, and Brucella. E. coli is a common urinary tract pathogen, but is not a usual cause of SBE. (Answer: all except c)

2. Preferred IV treatment regimens for SBE include:

a. S. viridans: Ceftriaxone + gentamicin x 2 weeks

b. E. faecalis: Vancomycin + gentamicin x 2 weeks

c. E. faecium: Vancomycin + gentamicin x 4 weeks

d. S. bovis: Ceftriaxone + gentamicin x 2 weeks

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Answer: Preferred IV therapy for S. viridans SBE is a 2-week course of ceftriaxone 2 gm (IV) q24h plus gentamicin 120 mg (IV) q24h. For E. faecalis, therapy consists of vancomycin 1 g (IV) q12h plus gentamicin 80 mg (IV) q8h x 4-6 weeks, not 2 weeks. E. faecium (VRE) is resistant to vancomycin, and should be treated with linezolid 600 mg (IV) q12h x 4-6 weeks. S. bovis is treated the same as S. viridans SBE. (Answer: a, d)

3. In patients with S. viridans SBE:

a. Vegetations and fever without positive blood cultures or peripheral manifestations of SBE is adequate for the diagnosis

b. Vegetations may persist after antibiotic therapy, but are sterile

c. It is important to repeat blood cultures to document clinical
 responsiveness, even if the patient defervesces and appears to be responding clinically
d. A minimum of 4 weeks of antibiotic therapy is required

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Answer: S. viridans endocarditis presents as a subacute febrile illness " localizing symptoms/signs in a patient with a heart murmur. Peripheral manifestations (e.g., clubbing, splenomegaly, petechiae) are often absent with early diagnosis and treatment. Diagnosis is confirmed by positive blood cultures plus a cardiac vegetation on transthoracic or transesophageal echo; vegetations without positive blood cultures or peripheral manifestations of SBE are not diagnostic of endocarditis. Cardiac valve/mural vegetations may persist after antibiotic therapy, but are sterile. Weekly ESRs should be followed to monitor antibiotic response; repeat blood cultures are not required unless the patient has persistent fevers or is not responding clinically. A 2-week course of antibiotics is acceptable for uncomplicated S. viridans SBE. Prognosis is related to the extent of embolization and severity of heart failure, although cure rates generally exceed 90%. (Answer: b)

4. All of the following statements about SBE are true except:

a. S. bovis SBE is often associated with GI polyp or tumor

b. Enterococcal SBE commonly follows GI/GU instrumentation

c. Non-enterococcal Group D streptococci (S. bovis) is penicillin-sensitive, unlike Group D enterococci (E. faecalis)

d. Most cases of "culture-negative" SBE are not really culture negative, but are due to fastidious organisms requiring prolonged incubation with enhanced CO₂ atmosphere for growth

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Answer: The most common SBE pathogens following GI/GU instrumentation are enterococci, especially E. faecalis. S. bovis is responsible for 10% of endocarditis cases, and is often associated with colonic polyps (65%) or malignancy (20%). S. bovis is sensitive to penicillin, unlike E. faecalis. Most cases of culture-negative SBE are not really culture negative, but are due to fastidious organisms (HACEK group), which require CO₂/special media (Castaneda vented bottles) and prolonged incubation (2-4 weeks) for growth. (Answer: all are true)

 5. Usual acute bacterial endocarditis (ABE) and prosthetic valve endocarditis (PVE) pathogens include:

a. S. aureus for ABE in normal hosts

b. S. aureus and P. aeruginosa for ABE in IV drug abusers

c. S. viridans in early PVE

d. S. viridans and S. epidermidis in late PVE

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Answer: S. aureus is the most common cause of ABE (in normal hosts and IV drug abusers), and is the most common cause of early PVE (within 60 days of prosthetic valve replacement). S. aureus endocarditis is a severe infection (esp. in non-addicts), affects normal and abnormal valves, and is associated with multiple metastatic abscesses. S. viridans and S. epidermidis are common causes of late PVE. S. viridans is a common cause of SBE and late PVE, but not early PVE. (Answer: c)

6. Which of the following statements about acute bacterial endocarditis are true:

a. Methicillin-sensitive S. aureus (MSSA) endocarditis in normal hosts can be effectively treated with IV naficillin or meropenem or imipenem

b. ABE should be treated for 2-4 weeks in normal hosts and 4-6 weeks in IV drug abusers

c. Tricuspid valve endocarditis is more common in IV drug abusers than normal hosts, and is often associated with multiple septic emboli

d. Janeway lesions (nontender hemorrhagic lesions of the palms and soles), splenomegaly, and clubbing are more common in ABE than SBE

e. Teichoic acid antibody levels should be followed weekly in S. aureus ABE, and fall (along with the ESR) with effective therapy

f. Premature closure of the anterior mitral leaflet is an early sign of impending mitral valve regurgitation

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Answer: Patients with ABE are critically ill with high fever (except in some elderly patients or those with severe heart failure or renal failure) and cardiac vegetations. Due to the fulminant nature of ABE, a baseline echocardiogram should be obtained to watch for/identify valve destruction, heart failure, and ring/perivalvular abscesses; premature closure of the mitral valve leaflet signifies impending aortic valve regurgitation. Preferred IV therapy for ABE due to MSSA consists of a 4-6 weeks of nafcillin 2 gm (IV) q4h or meropenem 1 gm (IV) q8h or imipenem 1 gm (IV) q6h. ABE and PVE require a minimum of 4 weeks of antibiotic therapy. S. aureus ABE should be followed with weekly teichoic acid antibody levels, which fall along with the ESR with effective therapy. Janeway lesions (caused by septic embolic) are usually seen in ABE, whereas splenomegaly, clubbing of the fingers, and petechiae are more common in SBE. More than 70% of IV drug abusers with right-sided (tricuspid valve) endocarditis have associated septic pulmonary emboli mimicking pneumonia. Compared to S. aureus endocarditis in non-addicts, S. aureus endocarditis in IV drug abusers is usually less severe and associated with a better prognosis if not complicated by abscess, valve regurgitation, or heart failure. (Answer: a, c, e)

7. Which of the following statements about prosthetic valve endocarditis (PVE) are true:

a. Valve removal is always necessary for cure of early and late PVE

b. In late PVE, culture of the removed valve may be negative, but valve gram stain is usually positive

c. PVE is equally common after replacement of a non-infected or infected native valve

d. Most cases of late PVE occur 6-12 months post-operatively

e. The mortality rate for early PVE is higher than late PVE

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Answer: Patients with early PVE improve clinically on treatment, but are not cured without valve replacement. Valve removal may be necessary for late PVE due to S. epidermidis, but is not always required. Culture of the removed valve may be negative, but valve gram stain is usually positive. Late PVE usually presents 18-24 months after valve replacement, and occurs more commonly after replacement of an infected native valve than a non-infected valve (4% vs. 0.5% per patient-year), although not necessarily with the original pathogen. Early PVE resembles ABE, and is a more serious infection than late PVE, manifesting a more fulminant course and high mortality rates (~ 30%); late PVE resembles S. viridans SBE clinically. (Answer: b, e)

8. Endocarditis prophylaxis is:

a. Directed against S. viridans from the mouth for above-the-waist procedures

b. Directed against Enterococci for below-the-waist procedures

c. Fully protective is given properly

d. Preferred via the parenteral route for patients with previous endocarditis, shunts, or rheumatic valve disease

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Answer: Endocarditis prophylaxis is designed to prevent native/prosthetic cardiac valve infections by preventing procedure-related bacteremias due to cardiac pathogens. For procedures above-the-waist, usual pathogens are viridans streptococci from the mouth. For procedures below-the-waist, usual pathogens are enterococci. Since procedure-related bacteremias are usually asymptomatic and last less than 15 minutes, single-dose oral regimens prior to the procedure usually provide effective prophylaxis. Parenteral SBE prophylaxis is preferred for patients with previous endocarditis, shunts, or prosthetic heart valves. Regimens vary among the experts, and no regimen is fully protective. (Answer: a, b)

9. Which of the following patient-procedure combinations require endocarditis prophylaxis:

a. Patient with ostium primum atrial septal defect (ASD) undergoing Cesarean section

b. Patient with previous rheumatic fever without valve disease undergoing cholecystectomy

c. Patient with previous endocarditis undergoing flexible bronchoscopy with biopsy

d. Patient with MVP with valvular regurgitation undergoing urethral catheterization in the presence of a UTI

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Answer: Endocarditis prophylaxis is indicated for patients with cardiac conditions in Column A undergoing procedures in Column A in the table below. Prophylaxis is not recommended for patients or procedures in Column B. (Answer: d)

10. Appropriate endocarditis prophylaxis regimens include:

a. Above-the-waist procedures: Amoxicillin 1 gm (PO) 1 hour preprocedure

b. Above-the-waist procedures, prior anaphylactic reaction to penicillin: Cephalexin 1 gm (PO) 1 hour preprocedure

c. Below-the-waist procedures: Amoxicillin 2 gm (PO) 1 hour preprocedure

d. Below-the-waist procedures, prior endocarditis: Amoxicillin 2 gm (PO) 1 hour preprocedure

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Answer: a, c (see Tables 1 and 2, below)