Internal Medicine_Infectious Diseases_15

Question 2

What is the most common cause of inflammatory cardiac disease of any pathogen?

Answer 2

Staphylococcus aureus

Increased risk with IV drug users, prosthetic valves, and cardiac devices.

Staphylococcus aureus is the leading cause of prosthetic valve IE, and typically causes acute (sudden onset over subacute) disease with rapid onset of high fever, and severe constitutional symptoms.

Question 3

Infectious endocarditis secondary to Staphylococcus aureus commonly has what systemic complication?

Answer 3

Septic emboli (PE in lungs)

Question 4

What are the most common locations of infective endocarditis (IE) in order of frequency?

Answer 4

1. Mitral valve
2. Aortic valve
3. Tricuspid valve (common in IV drug users)

Question 5

Following Staphylococcus aureus, what is the second most common pathogen that causes Infectious endocarditis in IV drug users?

Answer 5

Candida

Question 6

What are the common risk factors for infective endocarditis?

Answer 6

Prosthetic valves
Cardiac devices
Valvular disease (e.g., mitral valve prolapse, rheumatic heart disease)
Congenital heart disease
IV drug use (IVDU)
Poor dental hygiene or recent dental procedures

Question 7

What is the major causative organism of infective endocarditis secondary to gingival manipulation and poor dentition?

Answer 7

Streptococcus viridans (usually subacute).

HACEK organisms (rare).

Question 8

What is the major causative organism of infective endocarditis secondary to either UTIs or genitourinary procedures (cytoscopy)?

Answer 8

Enterococcus spp (usually subacute)

Can be right-sided or left-sided.

Question 9

What is the major causative organism of infective endocarditis secondary to colon cancer?

Answer 9

Streptococcus gallolyticus (bovis)

Question 10

What is the major causative organism of infective endocarditis secondary to prosthetic devices?

Answer 10

Coagulase-negative Staphylococci (S. epidermitis)

Coagulase-negative staphylococci (e.g, S. epidermidis), which have the ability to adhere to foreign bodies and form a biofilm, are a common cause of early-onset prosthetic valve IE (i.e., ≤ 12 months following surgery) or venous catheters. IE due to S. epidermidis typically has an insidious onset with a subacute disease course.

Even though the course can be subacute, symptoms will usually manifest early following surgical interventions (days to weeks).

Question 11

What is the major causative organism of infective endocarditis in immunocompromised patients?

Answer 11

Candida or other fungal pathogens.

Question 12

What is the major causative organism of infective endocarditis secondary to animal exposure?

Answer 12

Brucella or Coxiella

These are implicated in about 5% of native infective endocarditis.

Question 13

What are the clinical features of infective endocarditis?

Answer 13

Dyspnea (SOB), cough, pleuritic chest pain.

Constitutional symptoms: Fever, weight loss, night sweats.
Cardiac: New murmur or worsening of preexisting murmur.
Vascular phenomena: Splinter hemorrhages, Janeway lesions.
Immunologic phenomena: Osler nodes, Roth spots, glomerulonephritis.

Question 14

What is the Modified Duke Criteria for the diagnosis of infective endocarditis?

Answer 14

2 major criteria

OR

1 major + 3 minor criteria

OR

5 minor criteria

Question 15

What are the major criteria for the Modified Duke Criteria?

Answer 15

1.Echocardiographic evidence.

2.Positive blood cultures
- typical organisms: 2 cultures drawn >12 hours apart.
- nontypical organisms: 3 cultures with the 1st and last drawn at least 1-hr apart

3.Serology from a culture negative organism (>1:800)
- Coxiella
- Bartonella
- Tropheryma whipplei

Question 16

What are the minor criteria for the Modified Duke Criteria?

Answer 16

Predisposing factor (e.g., congenital heart disease, prosthetic valve, IV drug use).
Fever >38°C.
Vascular events (e.g., Janeway lesions, arterial emboli, septic infarcts).
Immunologic events (e.g., Osler nodes, Roth spots, RF).
New valvular regurgitation.
Atypical blood culture or serology.

Question 17

How is infective endocarditis managed?

Answer 17

First: Obtain 3 sets of blood cultures before starting antibiotics.

Second: Empiric therapy for acutely ill patients: Vancomycin ± gentamicin.

Third: Transition to pathogen-specific antibiotics once cultures are available (typically 4–6 weeks total therapy).

Last: Surgery if severe valve dysfunction, abscess, or persistent infection.

Question 18

What are complications of infective endocarditis?

Answer 18

Heart failure
Perivalvular abscess (conduction defects or persistent bacteremia)
Septic emboli (e.g., strokes, pulmonary infarcts)
Mycotic aneurysms
Glomerulonephritis

Question 19

When is prophylaxis for infective endocarditis indicated?

Answer 19

When an invasive procedure is performed and a specific history involving infective endocarditis.

Question 20

Which invasive procedures, following a specific history of infective endocarditis, call for prophylaxis with antibiotics?

Answer 20

Dental procedures involving gingival manipulation such as an extraction, implants, peridontal, and cleanings (due to risk of gingival bleeding).

Respiratory biopsy.

Procedures on infected GI/GU tract or skin.

Heart surgery involving prosthetic valves or intracardiac materials.

The most commonly used antibiotic regimen is oral amoxicillin administered 30–60 minutes prior to a high-risk procedure. Alternatives to amoxicillin include intravenous ampicillin in patients unable to take oral medication and azithromycin in patients allergic to penicillin.

Question 21

What specific past heart issues call for prophylaxis with antibiotics due to an increased risk of infective endocarditis?

Answer 21

Implantation of prosthetic valves or cardiac material.

History of endocarditis.

Unrepaired cyanotic congenital heart disease.

Question 22

In relation to infective endocarditis, is prophylaxis with antibiotics warranted when a patient has a limb prosthesis?

Answer 22

No

Question 23

Prophylaxis due to specific history in relation to infective endocarditis, is with which antibiotics?

Answer 23

Prophylactic regimen: Amoxicillin.

Alternatives: cephalexin, clindamycin, azithromycin.

Question 24

A 30-year-old IV drug user presents with fever and a new murmur. Blood cultures grow gram-positive cocci in clusters. What is the most likely pathogen, and which valve is likely affected?

Answer 24

Pathogen: Staphylococcus aureus
Valve: Tricuspid
Treament: Vancomycin

Question 25

A 65-year-old male with a history of colon cancer presents with fatigue, fever, and a new murmur. Blood cultures grow Streptococcus gallolyticus (bovis). What is the next best step in management?

Answer 25

Perform a colonoscopy to evaluate for malignancy or polyps.

Streptococcus gallolyticus can be found in the normal bowel flora of healthy humans. A link between S. gallolyticus bacteremia, particularly in endocarditis, and colorectal cancer has been well established. However, it remains unclear whether this pathogen is part of the etiology of colorectal malignancies or a consequence of the disease. A colonoscopy is indicated in all patients with S. gallolyticus on blood culture.

Question 26

A patient with a prosthetic valve develops fever, weight loss, and positive blood cultures for coagulase-negative staphylococci. What is the most appropriate initial treatment?

Answer 26

Empiric antibiotics: Vancomycin + Rifampin ± Gentamicin.

Question 27

A patient with fever, Osler nodes, and Janeway lesions meets 1 major Duke criterion and 2 minor criteria. Is this sufficient for a definite diagnosis of infective endocarditis?

Answer 27

No. To meet criteria for definite IE:

2 major OR 1 major + 3 minor OR 5 minor are required.

Question 28

A 45-year-old woman presents with fever, weight loss, and fatigue. She has a history of mitral valve prolapse. Physical examination reveals splinter hemorrhages and a new systolic murmur. Blood cultures are pending. What is the next best step in management?

A) Start broad-spectrum antibiotics.
B) Obtain 3 sets of blood cultures.
C) Perform echocardiography.
D) Prescribe prophylactic antibiotics.

Answer 28

B) Obtain 3 sets of blood cultures.

Explanation: Blood cultures should always be obtained before starting antibiotics to improve diagnostic yield. Empiric antibiotics can be started after cultures are drawn.

Question 29

A 60-year-old man with a history of aortic valve replacement presents with fever, chills, and confusion. Blood cultures grow Staphylococcus epidermidis. Echocardiography reveals a 1.5 cm vegetation on the prosthetic valve. What is the definitive treatment?

A) High-dose vancomycin for 6 weeks.
B) Rifampin for 4 weeks and gentamicin for 2 weeks.
C) Surgical valve replacement.
D) Amoxicillin for 6 weeks.

Answer 29

C) Surgical valve replacement.

Explanation: Prosthetic valve endocarditis with large vegetations and systemic symptoms often requires surgical intervention in addition to antibiotics. Indications for aortic valve replacement in IE include severe destruction of the valve, leading to aortic regurgitation and heart failure, persistent infection despite appropriate antibiotic treatment, and infections with difficult-to-treat pathogens (e.g., fungi, resistant organisms), among others. If a patient makes made a full recovery following antibiotic therapy and a repeat echocardiography shows only mild aortic regurgitation, surgery would not indicated.

Question 30

A 32-year-old man presents with fever and hematuria. Blood cultures grow Enterococcus faecalis. What is the most likely predisposing factor, and how should this patient be managed?

A) Recent dental procedure; treat with vancomycin.
B) IV drug use; treat with ceftriaxone.
C) Genitourinary manipulation; treat with ampicillin and gentamicin.
D) Colon cancer; treat with ceftriaxone and doxycycline.

Answer 30

C) Genitourinary manipulation; treat with ampicillin and gentamicin.

Explanation: Enterococcal endocarditis is often associated with genitourinary procedures or infections. The combination of ampicillin and gentamicin provides synergistic activity.

Note: Ampicillin can be replaced with Penicillin G.

Note: Treatment regimen can be with Ampicillin and Ceftriaxone.

Note: with penicillin resistance, treat with Vancomycin and Gentimicin.

Question 31

A 28-year-old IV drug user presents with fever and a new systolic murmur. Transthoracic echocardiography (TTE) is inconclusive. What is the next best imaging study?

A) Chest X-ray.
B) CT scan of the chest.
C) Transesophageal echocardiography (TEE).
D) Repeat TTE in 48 hours.

Answer 31

C) Transesophageal echocardiography (TEE).

Explanation: TEE is more sensitive than TTE for detecting vegetations and is the preferred imaging modality when TTE is inconclusive.

Question 32

A 52-year-old man presents with a 2-week history of fever and malaise. Blood cultures grow Streptococcus viridans. Modified Duke Criteria are met for infective endocarditis. What is the standard antibiotic regimen for this patient?

A) Vancomycin for 4–6 weeks.
B) Ceftriaxone for 2 weeks.
C) Penicillin G ± gentamicin for 4–6 weeks.
D) Amoxicillin for 2 weeks.

Answer 32

C) Penicillin G ± gentamicin for 4–6 weeks.

Explanation: Native valve endocarditis caused by Streptococcus viridans is typically treated with penicillin G, often combined with gentamicin for synergistic activity.

Note: Viridans is the second most common cause of native valve infective endocarditis while S. aureus is the most common.

Note: an alternative to these antibiotics is Vancomycin.

Question 33

A 70-year-old man presents with a history of fever, a new murmur, and a petechial rash. Echocardiography shows a vegetation on the mitral valve. Blood cultures are negative after 48 hours. What is the most likely cause?

A) Recent antibiotic use.
B) Infection with HACEK organisms.
C) Coxiella burnetii infection.
D) Staphylococcus epidermidis.

Answer 33

A) Recent antibiotic use.

Explanation: Negative blood cultures in infective endocarditis are commonly due to prior antibiotic use. Rarely, fastidious organisms like HACEK or Coxiella burnetii can also cause culture-negative endocarditis.

Question 34

Infective endocarditis secondary a HACEK organism (Haemophilus genus, Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae) is treated with … ?

Answer 34

Ceftriaxone

Alternatively: Cefepime, Ampicillin or Ciprofloxacin

Note: use Ampicillin only if in vitro susceptibility has been proven.

Question 35

A 35-year-old woman with a history of cyanotic congenital heart disease undergoes a dental extraction. What prophylactic antibiotics should she receive, and why?

A) None; prophylaxis is not indicated.
B) Ceftriaxone to prevent Staphylococcus aureus.
C) Amoxicillin to prevent Viridans streptococci.
D) Vancomycin to prevent Enterococcus faecalis.

Answer 35

C) Amoxicillin to prevent Viridans streptococci.

Explanation: Patients with cyanotic congenital heart disease are at risk for endocarditis, particularly with dental procedures. Amoxicillin is the first-line prophylactic antibiotic for Viridans streptococci.

Question 36

What pathogens are most commonly implicated in Central line-associated bloodstream infection?

Answer 36

Staphylococci such as S. aureus account for the majority of cases of healthcare-associated IE.

Rapid progression and an acute onset of symptoms is usually S. aureus. Acute IE due to S. aureus can quickly lead to complications such as valvular insufficiency, heart failure, and septic emboli. Therefore, in addition to removing the infected CVC, empiric antibiotic therapy (vancomycin plus beta-lactam for native valve endocarditis) should be initiated after obtaining blood cultures.

Coagulase-negative staphylococci (e.g., S. epidermidis), S. aureus, enterococci, and Candida spp. are the organisms most commonly associated with CLABSI with a more insidious progression (weeks to months) with low-grade fever and nonspecific symptoms.

Question 37

Is Streptococcus pneumoniae a common cause of IE?

Answer 37

No.

Streptococcus pneumoniae is a very rare cause of IE, although it is more commonly seen in patients with underlying conditions such as HIV, cirrhosis, asthma and diabetes mellitus.

Question 38

What pathogen is the most common cause of subactue infective endocarditits?

Answer 38

Viridans streptococci (e.g. S. sanguinis, S. mutans, S. salivarius, S. mitis, and S. anginosus) are the most common cause of subacute IE and generally affect individuals with preexisting damage to the heart valves, structural heart defects, or prosthetic valves. These organisms are usually precluded in IE in associated with prosthetic valves where Coagulase-negative staphylococci (e.g, S. epidermidis) is usually implicated.

IE due to infection with viridans streptococci typically occurs > 1 year after valve replacement (i.e., late-onset IE).

Subacute IE, which is characterized by an insidious onset (weeks to months) and less severe constitutional symptoms (e.g., low-grade fever), is most commonly caused by viridans streptococci.

Question 39

If blood cultures drawn from a patient with suspected IE (with a prosthetic valve) confirm infection with methicillin-susceptible Staphylococcus epidermidis, what is the most appropriate pharmacotherapy?

Answer 39

Intravenous therapy with nafcillin and rifampin for at least 6 weeks in combination with gentamicin for 2 weeks is the treatment of choice for prosthetic valve IE due to methicillin-susceptible staphylococci. Treatment with gentamicin is restricted to 2 weeks because the risk of renal toxicity increases with duration of therapy. Prosthetic valve IE generally requires a longer duration than native valve IE.

Prosthetic valve IE caused by methicillin-resistant staphylococci should be treated with an intravenous combination of vancomycin, rifampin, and gentamicin.

Question 40

What is the treatment for Staphylococcus epidermidis IE on a native valve?

Answer 40

Intravenous gentamicin and penicillin G are effective in the treatment of native valve IE caused by penicillin-susceptible gram-positive cocci as long as there are no complications, such as perivalvular abscess. If the response to therapy is adequate (resolution of fever, chills), a 2-week course is sufficient.

Question 41

What are the two forms of S. aureus of IE and how are they treated differently?

Answer 41

MSSA (Methicillin-susceptible)
For native valve: Oxacillin, Nafcillin or Cefazolin
For Prosthetic valves: Oxacillin or Nafcillin WITH Rifampin and Gentamicin

MRSA (Methicillin-resistant)
For native valve: Vancomycin
For Prosthetic valves: Vancomycin WITH Rifampin and Gentamicin

Question 42

What makes a pulmonary septic emboli secondary to Staphylococcus aureus more common than Roth spots, Janeway lesions, embolic arterial occlusion of the kidney, brain, and spleen?

Answer 42

Septic pulmonary embolism is a common and severe complication of right-sided IE from the tricuspid valve in the heart and is caused by bacterial thromboemboli that form and dislodge into the lung. Patients present with cough, pleuritic chest pain, and nodular pulmonary infiltrates. While tricuspid valve IE is rare, nonsterile injections (e.g., in individuals who use IV drugs) leading to bacteremia as well as indwelling intravascular devices increase the risk for this condition.

Question 43

Osler nodes are more common in _____ IE.

Answer 43

Osler nodes are more common in protracted IE.

Osler nodes typically occur in protracted cases of IE. These are painful nodules on the pads of the fingers as a result of circulating immune complex deposition in the skin and are a relatively rare but highly suggestive finding of IE.

Question 44

When this is seen along with a heart murmur, think ….

Answer 44

Infective endocarditis. Hemorrhages underneath the fingernails (i.e., splinter hemorrhages) are a common finding in IE and are caused by septic microemboli from infected heart valves.

Immune complex deposition or microthrombosis occurs in subacute, infective endocarditis, as well as with SLE, or rheumatoid arthritis.

Question 45

What eye finding is associated with infective endocarditis?

Answer 45

Retinal hemorrhages with pale centers (i.e., Roth spots) are highly suggestive of IE.

This is a rare finding.

Question 46

What vascular symptom is associated with infective endocarditis?

Answer 46

Janeway lesions are typically caused by septic microembolisms secondary to infective endocarditis.

Question 47

Why is gentamicin not a great antibiotic for the treatment of a HACEK organism (Haemophilus genus, Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae) ?

Answer 47

Gentamicin is effective against gram-negative bacteria including HACEK organisms. However, gentamicin is both nephrotoxic and ototoxic, and the risk of developing one or more of the side effects of gentamicin is considerably higher if used for longer than 2 weeks. Since antibiotic therapy would be indicated for a minimum duration of 4 weeks in the case of infective endocarditis caused by a HACEK organism, a different antibiotic regimen is preferred, such as ceftriaxone.

Question 48

Is thrmobolytic therapy recommended for septic emboli?

Answer 48

Thrombolytic therapy is not recommended for patients with IE and embolic stroke because of the risk of cerebral hemorrhage. Empiric antibiotic treatment, which reduces the risk of recurrent embolism, should be initiated after collecting three sets of blood cultures. Moreover, evaluation of the brain with a noncontrast CT is indicated to rule out hemorrhage. Cardiothoracic surgery may be necessary for complicated IE.

Question 49

Echocardiographic evidence of IE is generally collected with … ?

Answer 49

Transthoracic echocardiography is typically performed first, since it is a much less invasive test.

Question 50

Streptococcus pyogenes would be considered a typical or nontypical bacterial cause for IE?

Answer 50

nontypical

Streptococcus pneumoniae is also nontypical.