PBL Case 1

Question 1

MOA Ceftriaxone:

Answer 1

• Inhibits cell wall synthesis

- Binds to penicillin binding proteins, inhibiting peptidoglycan synthesis

Question 2

MOA Vancomycin:

Answer 2

• Inhibits cell wall synthesis
• Forms H bonds w/ D-alanyl-D-alanine moiety of the NAM/NAG peptide, which normally forms the backbone of the bacterial cell wall

Question 3

MOA Penicillin G:

Answer 3

• Inhibits cell wall synthesis

- Beta-lactam ring binds to DD-transpeptidase inhibiting cross-linking & remodeling of peptidoglycan

Question 4

MOA tPA:

Answer 4

• Can cause hemorrhagic conversion

- Converts plasminogen to plasmin which breaks up clots

Question 5

What are the most common organisms that cause acute endocarditis?

Answer 5

1. Staph. aureus

2. Strep. pyogenese

Question 6

What are the most common organisms that cause subacute endocarditis?

Answer 6

1. Streptococcal species (viridians)

2. Enterococci

Question 7

What is the most common endocarditis cause in IV drug users?

Answer 7

Staph. aureus

Question 8

Describe the normal flow of blood through the cardiac chambers and normal function of the four cardiac valves:

Answer 8

1. Blood enters the right atrium from superior and inferior vena cavae.
2. Blood in right atrium flows through right AV valve (tricuspid) into right ventricle.
3. Contraction of right ventricle forces pulmonary valve open.
4. Blood flows through pulmonary valve into pulmonary trunk
5. Blood is distributed by right and left pulmonary arteries to the lungs, where it unloads CO2 and loads O2.
6. Blood returns from lungs via pulmonary veins to left atrium.
7. Blood in left atrium flows through left AV valve (mitral/bicuspid) into left ventricle.
8. Contraction of left ventricle (simultaneous with step 3) forces aortic valve open
9. Blood flows through aortic valve into ascending aorta.
10. Blood in aorta is distributed to every organ in the body, where it unloads O2 and loads CO2.
11. Blood returns to the heart via venae cave.

Question 9

What are the virulence factors of Staph Aureus?

Answer 9

• Biofilm formation
• Protein A (binds Fc portion of IgG)
• Coagulase - activates fibrinogen
• Capsule
• Adhesins
• Pathogenicity Islands (Methicillin Resistance)

Question 10

What are the virulence factors for Strep. viridians?

Answer 10

(strep. mutans)
- Needs some kind of damage for colonization event
- Makes Dextran for Glycolcalyx formation and surface adhesion proteins for colonization.

-M protein keeps bacteria from being phagocytosed and the complement-activation cascade

Question 11

How does bacterial endocarditis cause a murmur?

Answer 11

1. Colonization on the heart valve
2. Mitral valve regurgitation
3. Turbulent flow
4. Murmur

Question 12

ECHO (transthoracic echocardiogram)

Answer 12

Superior for imaging structures that are thin and highly mobile owing to its greater temporal resolution and the absence of partial volume effects

Question 13

TEE (transesophageal echocardiography)

Answer 13

1. Used when there is an inability to get clear imagine through standard ECHO
2. TEE provides more detailed information on the size, shape and movement of heart muscle, the condition of aorta, how the heart valves are working and the quality of blood flow through the heart and arteries
3. Done with a swallowed probe; more expensive, higher risk

Question 14

Cardiovascular magnetic resonance (CMR):

Answer 14

1. Has potential to visualize all parts of the valve (leaflets, chord tendineae, and papillary muscles) throughout the entire cardiac cycle. Congenitally abnormal valve leaflets (bicuspid), aberrant papillary muscles, etc. have all been reported by CMR.
2. 2D echocardiography remains the primary approach for visualization of valve anatomy. But CMR is a reasonable alternative if ultrasound windows are poor.

Question 15

What are the properties of S. mutans?

Answer 15

Alpha hemolytic
Bacitracin resistant
Catalase - 
Cocci
Gram +

Question 16

What are the properties of S. pyogenes?

Answer 16

Beta hemolytic
Bacitracin sensitive
Catalase - 
Cocci
Gram +

Question 17

What is gamma hemolysis?

Answer 17

Doesn’t damage RBC at all, no color change

Question 18

What is alpha hemolysis?

Answer 18

Strep. Viridans

Partial degradation of RBCs, leads to color change/oxidation and turns surrounding area green

Question 19

What is beta hemolysis?

Answer 19

Group A strep (streptococcus pyogenese)

-Completely destroys RBCs

Question 20

Describe the relationship between endocarditis and stroke:

Answer 20

Vegetation (bacteria + fibrin mesh) break off from the valve and travel to other parts of the body, blocking blood flow.

• Risk of embolization is highest during first week of therapy and in patients with mobile vegetations or vegetations >10 mm in diameter occurring on the mitral valve.
• Endocarditis can also lead to hemorrhaging in the brain and other pats of the body via septic erosion of arterial walls!

Question 21

What is the overall stroke risk in patients with endocarditis?

Answer 21

9.1% in 12 months after diagnosis

Question 22

What is the MOA for tPA and Streptokinase?

Answer 22

tPA - converts plasminogen to plasmin which degrades fibrin clots
Streptokinase - biosynthetic form of tPA

Question 23

What are the benefits and risks of tPA and streptokinase?

Answer 23

Risks: intracranial hemorrhage within first 7 days after admin.
Benefits: inc. functional independence without affecting mortality at 3-6 months if given within 3 hours

Question 24

What are contraindications of tPA and streptokinase?

Answer 24

Suspected/confirmed endocarditis, intracranial hemorrhage on CT, clinical presentation suggests subarachnoid hemorrhage, neurological surgery, head trauma or stroke in past 3 months, uncontrolled hypertension, hx of intracranial hemorrhage, seizure at stroke onset, known arteriovenous malformation, neoplasm, aneurysm, abnormal blood glucose

Question 25

What evidence supports the genetic risk for development of rheumatic fever?

Answer 25

Monozygotic and dizygotic twin studies

Question 26

What differentiates PTSD from a generalized anxiety and/or cardiac symptoms?

Answer 26

Prior trauma

Question 27

How to differentiate between PTSD and generalized anxiety?

Answer 27

PTSD - traumatic situations outside the usual human experience (gunshot wound, loss of children in traumatic way, refugee status) -In our case, the length of symptoms being experienced rules out adjustment disorder

Question 28

What are the 6 traits of which you need 3 for generalized anxiety?

Answer 28

For GAD: General worry, and inability to control the worry. Need three/six for diagnosis: 1. restlessness or feeling keyed up or on edge 2. being easily fatigued 3. difficulty concentrating or mind going blank 4. irritability 5. muscle tension 6. sleep disturbance (difficulty falling or staying asleep, or restless unsatisfying sleep)

Question 29

Define generalized anxiety disorder:

Answer 29

- Lasts more than 6 months unrelated to a specific person, situation or event - Associated with sleep disturbance, fatigue, GI disturbance, difficulty concentrating

Question 30

What is adjustment disorder?

Answer 30

Emotional symptoms (anxiety, depression) causing impairment following identifiable psychosocial stressor (e.g., divorce, illness) and lasting 6 months in presence of chronic stressor)

Question 31

What tests can be used to rule out heart problems when someone has anxiety?

Answer 31

- EKG , bloodwork, echo, and stress test & holter monitor is enough to rule out significant heart problems - Ask patient if there is a triggering event, situation, emotional state

Question 32

What do you HAVE to do before giving prophylactic antibiotics?

Answer 32

Draw for blood cultures!!

Question 33

What is the tPA mechanism?

Answer 33

- Plasminogen --> Plasmin - Plasmin degrades clot into FDPs (fibrin degradation products) - Ischemic stroke due to breaking off and lodging of vegetation. tPA likely most effective when vegetation has large number of platelets - tPA (alteplase) use is not agreed upon by professional societies and use is highly dependent on clinical situation, although some guidelines exist - generally not recommended bc so many patients hemorrhage