Bacteremia and Infective Endocarditis

Question 1

Transient bacteremia:

Answer 1

Occurs during normal daily activities (toothbrushing, bowel movements).

Question 2

Intermittent bacteremia:

Answer 2

Occurs with infection and obstruction (pyelonephritis, cholecystitis), and undrained abscesses

Question 3

Continuous (“high-grade”) bacteremia:

Answer 3

Endovascular infections: endocarditis, infected arterial aneurysms, infected grafts and shunts

Question 4

Interpretation of blood cultures:

Answer 4

Normal skin flora are usually contaminants: (coagulase-negative staph, Bacillus, proionibacterium acnes, viridans strep)
True pathogens are rarely contaminants:
(gram-negative bacilli, S. aureus, anaerobes, S. pyogenes, S. pneumoniae)

Question 5

When to suspect that an organism is a contaminant

Answer 5

Clinical course is not suggestive of bacteremia
Primary infection with the same organisms is not found
Predisposing factors are absent
There is no leukocytosis or left shift

Question 6

Acute endocarditis:

Answer 6

May occur on normal or abnormal valves
Acute onset, hectic pace, early complications
Caused by virulent organisms (S. aureus, beta-hemolytic strep, pneumococcus)

Question 7

Subacute endocarditis:

Answer 7

Usually occurs on abnormal valves
Subacute onset (months), insidious course
Caused by less virulent organisms (Viridans strep, coagulase-negative staph)

Question 8

Factors predisposing to native valve IE:

Answer 8

Injection drug use
Mitral valve prolapse
Degenerative valve disease
Rheumatic heart disease
Poor dental hygiene
Long-term hemodialysis
Previous endocarditis

Question 9

Staph aureus IE:

Answer 9

Nosocomial, IDU

Question 10

Coagulase-negative staph IE:

Answer 10

Medical interventions

Question 11

Enterococci IE:

Answer 11

Bladder outlet obstruction

Question 12

Polymicrobial IE:

Answer 12

IDU

Question 13

Culture-negative IE:

Answer 13

Due to recent antibiotic treatment or fastidious organisms

Question 14

Manifestations of SBE:

Answer 14

FEVER (>95%), anorexia, weight loss, malaise, night sweats, MYALGIA, HEART MURMURS (may be pre-existing), embolic stigmata (petechiae), splenomegaly, major emboli, SPLENIC INFARCTS, renal manifestations

Question 15

Manifestations of ABE:

Answer 15

Abrupt onset, HIGH FEVER, RIGORS, prominent cutaneous manifestations, visceral emboli, CHANGING HEART MURMUR (signifies rapid valve destruction), rapid development of CHF

Question 16

IDU associated endocarditis:

Answer 16

Usually in people without congenital heart disease, S. aureus, Pseudomonas, polymicrobial, Candida, high frequency of TRICUSPID VALVE infection, fever, cough, chills, malaise, PLEURITIC chest pain from septic pulmonary emboli

Question 17

Prosthetic valve IE causes:

Answer 17

Early: Coagulase-negative staph
2-12 months: Coagulase-negative staph
>12 months: Streptococci

Question 18

Duke criteria:

Answer 18

Major criteria:
Microbiologic (typical organisms on 2 separate BCs or persistently positive BCs) OR
Evidence of endocardial involvement (new valvular regurgitation, positive echocardiogram)
Minor criteria:
Predisposition to IE (IDU, previous IE, heart disease, prosthetic valve), fever, vascular phenomenon, immunologic phenomenon (RF, glomerulonephritis, Osler’s nodes, Roth spots), microbiologic findings that don’t meet major criteria
Definite: 2 major or 1 major + 3 minor or 5 minor
Possible: 1 major + 1 minor or 3 minor

Question 19

Complications of IE:

Answer 19

Valve damage causing CHF, myocardial abscess, extension into septum causing heart block, purulent pericarditis, EMBOLI, mycotic aneurysm, spleen abscesses

Question 20

Susceptible viridans streptococci treatment:

Answer 20

Penicillin G or ceftriaxone (4 weeks)

Question 21

Resistant viridans streptococci treatment:

Answer 21

Penicillin G (4 weeks) + gentamicin (2 weeks)

Question 22

Enterococci, other streptococci treatment:

Answer 22

Penicillin G + gentamicin (2-6 weeks)

Question 23

MSSA treatment:

Answer 23

Nafcillin (4 weeks)

Question 24

MRSA treatment:

Answer 24

Vancomycin (4 weeks)

Question 25

HACEK organisms treatment:

Answer 25

(Hemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella)
Ceftriaxone (4 weeks)

Question 26

Prosthetic valve treatment:

Answer 26

6 weeks instead of 4. Add a second agent: gentamicin for sensitive strep, rifampin for MSSA, MRSA, coagulase-negative staph

Question 27

Indications for surgery in IE:

Answer 27

Persistent bacteremia despite therapy, perivalvular invasive disease, moderate/severe CHF, recurrent major emboli, large vegetations, specific organisms (Pseudomonas, fungi, resistant enterococci)

Question 28

Prophylaxis for high risk patients (history of endocarditis, prosthetic valves, cyanotic congenital heart disease):

Answer 28

Dental procedures, upper respiratory tract surgery, esophageal surgery, biliary tract surgery, intestinal surgery, UT surgery, surgery involving infected tissues

Question 29

Endocarditis principles of treatment:

Answer 29

Obtain blood cultures before treating.

Use high doses of parenteral agents (4 weeks for native valve endocarditis, 6 weeks for prosthetic valve endocarditis)

Question 30

Factors affecting mortality in IE:

Answer 30

Causative organism
Complications of co-existing conditions (CHF, neurologic events, renal failure)
Perivalvular extension
Appropriate surgical intervention
Much lower mortality rate with right-sided IE