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CRAAB 1 > Diebel: Micro Case I > Flashcards

Diebel: Micro Case I Flashcards

1
Q

How do you usually identify a causative infectious agent?

A
  1. Gram stain
  2. PCR- esp for viral infections
  3. Biochemical tests.
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2
Q

What is an API 20 Strep Test?

A

Specific strep species have a distinct biochemical profile. You can determine that profiile by growing them on different types of media, and looking at how they ferment particular sugars.

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3
Q

What type of organisms are capable of establishing infection in subacute endocarditis?

A

Less virvulent organisms can get a foot hold on PREVIOUSLY damaged heart valves.

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4
Q

What species commonly colonizes in subacute infections?

A

Strep spp in the bloodstream goes to colonize heart tissue and causes vegetations.

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5
Q

How does vegetation size differ in acute and subacute cases?

A

Vegetations are usually smaller in subacute form.

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6
Q

Is previous damage necessary for micro-orgs to take hold in the acute form of endocarditis?

A

NO

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7
Q

What is the most common form of acute endocarditis?

A

Staph aureus

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8
Q

What causes vascular phenomenon seen in endocarditis?

A

arterial emboli

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9
Q

What is a Janeway lesion?

A

Vascular phenomenon

Non-tender, palms and soles, lasts days -wks, common in acute

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10
Q

What causes immunological phenomenon seen in endocarditis?

A

d/t inflammation type III hypersensitivity

RF, Roth Spots, Osler nodes

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11
Q

What are osler nodes?

A

Tender, digits, last hours-days, bacteria can be isolated from early form but not late

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12
Q

What is the causative agent of rheumatic fever?

A

Strep pyogenes
Group B
beta hemolytic

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13
Q

What protein is unique to the strep pyogenes subspecies?

A

M protein (100+ variations)

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14
Q

How do different variations of M species relate to infection?

A

ONLY certain M proteins + certainly predisposed individuals > cross rxn w/ meromysin

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15
Q

What is the pathway to RHD?

A

Strep throat> Rheumatic Fever > RHD

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16
Q

How does a strep infection lead to rheumatic fever?

A

Type II hypersensitivity!

  1. Ab to M protein of previous s. pyogenes infection reacts with the surface of heart valve tissue.
  2. Complement pathway activation> tissue damage (further damaged via type II if pt gets endocarditis)
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17
Q

How does RF cause RHD?

A

Type III hypersensitivity

  1. Ab to M protein binds appropriately to bacteria
  2. Immune complex formation > Inflammation
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18
Q

In what region is the incidence of RHD lowest?

A

In places where strep throat is treated quickly

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19
Q

Why do surface proteins on streptococcus change?

A

Not all are expressed at once! Microbe expression depends on the region of colonization in the body > many different types of disease manifestations based on protein expression

20
Q

What are virulence factors?

A

Anything a microbe/virus uses to establish/prolong infection

21
Q

What VFs does streptococcus use?

A
  1. Dextran production/ glycocalyx formation

2. Surface adhesion proteins (FimA, GspB)

22
Q

VF for strep pneumoniae?

23
Q

VF for s. pyogenes?

A

Capsule

Protein M

24
Q

VF for neiserria meningitidis?

25
VF for s. aureus?
1. Capsule 2. Biofilm formation 3. Fibronectin binding proteins* 4. Coagulase 5. Leukocidin
26
VF for s. spidermidis?
Sd repeat containing protein G | Biofilim formation
27
VF for Cox A and B, Adenovirus?
Coxsackie-ADenovirus cellular receptor (CAR) binding protein
28
VF for Rickettsia RIckettsia?
OmnA and OmnB (attachment) | T4SS host cell entry
29
What are the three causes of type III hypersensitivity?
persistent infection autoimmunity inhaled antigen
30
What are the 4 types of hypersensitivity?
1. Allergy-Over produce IgE> over release of histamine> swelling/airway constriction 2. Cytotoxicity 3. Immune cell- Ab bound to foreing proteins, not enough Ab to get rid of Ag and settle in joints/vessels 4. Delayed- T cells don't recognize and attack
31
A pt. has a fever of 104, rash on arms legs and trunk, and only symptomatic tx is given. What do they have?
Myocarditis?
32
What cultures/serological test can be beneficial in diagnosing myocarditis?
Blood culture, if growth= gram stain, growth on blood agar plate, API test, ELISA
33
What do you use to determine the exact viral agent?
RT-PCR
34
What bug causes myocarditis and what VF does it use to cause disease?
Most likely Cox B. Can bind to the CAR receptor protein in the heart which is key for setting up the myocarditis infection seen here.
35
What is the triad for RMSF?
Fever Tick bite Rash
36
What causes RMSF?
Rickekrickettsaia
37
How does RMSF spread?
OmpA and B for adherence | T4SS for intracellular invasion
38
What cultures and serologic tests should be perform to definitively diagnose RMSF?
1. Indirect immunological assay (fluorescence/agglutination) 2. Skin biopsy 3. PCR for rickettsia DNA * clinical diagnosis w/ sx triad usually sufficient
39
How do you treat RMSF?
Doxycycline
40
What is the most helpful aspect of a pt hx that can assist in diagnosing RF?
Age 5-15 | Previous tx for strep throat
41
What VF are related to the pathogenesis of RF?
Damage to the heart muscle and valves is attributed to bacterial ags (protein M) that cross react with meromyosin in the heart. M protein resists phagocytosis and cause an autoimmune cross reaction.
42
What possible sequelae are associated with RF?
Heart valve damage | Infectious endocarditis
43
What is the most likely diagnosis for a pt with a recent viral URI, an arrythmia, pericardial friction rub, and elevated myocardial enzymes?
Pericarditis
44
What is the most likely causative org of pericarditis?
Cox A or B | Echo or influenza too
45
What tests should be performed for a definitive diagnosis?
RT-PCR
46
What is the proper course of tx for this infection?
Supportive (if viral origin)

CRAAB 1 (11 decks)

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