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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?

A

capsule

23
Q

VF for s. pyogenes?

A

Capsule

Protein M

24
Q

VF for neiserria meningitidis?

A

Capsule

25
Q

VF for s. aureus?

A
  1. Capsule
  2. Biofilm formation
  3. Fibronectin binding proteins*
  4. Coagulase
  5. Leukocidin
26
Q

VF for s. spidermidis?

A

Sd repeat containing protein G

Biofilim formation

27
Q

VF for Cox A and B, Adenovirus?

A

Coxsackie-ADenovirus cellular receptor (CAR) binding protein

28
Q

VF for Rickettsia RIckettsia?

A

OmnA and OmnB (attachment)

T4SS host cell entry

29
Q

What are the three causes of type III hypersensitivity?

A

persistent infection
autoimmunity
inhaled antigen

30
Q

What are the 4 types of hypersensitivity?

A
  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
Q

A pt. has a fever of 104, rash on arms legs and trunk, and only symptomatic tx is given. What do they have?

A

Myocarditis?

32
Q

What cultures/serological test can be beneficial in diagnosing myocarditis?

A

Blood culture, if growth= gram stain, growth on blood agar plate, API test, ELISA

33
Q

What do you use to determine the exact viral agent?

A

RT-PCR

34
Q

What bug causes myocarditis and what VF does it use to cause disease?

A

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
Q

What is the triad for RMSF?

A

Fever
Tick bite
Rash

36
Q

What causes RMSF?

A

Rickekrickettsaia

37
Q

How does RMSF spread?

A

OmpA and B for adherence

T4SS for intracellular invasion

38
Q

What cultures and serologic tests should be perform to definitively diagnose RMSF?

A
  1. Indirect immunological assay (fluorescence/agglutination)
  2. Skin biopsy
  3. PCR for rickettsia DNA
  • clinical diagnosis w/ sx triad usually sufficient
39
Q

How do you treat RMSF?

A

Doxycycline

40
Q

What is the most helpful aspect of a pt hx that can assist in diagnosing RF?

A

Age 5-15

Previous tx for strep throat

41
Q

What VF are related to the pathogenesis of RF?

A

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
Q

What possible sequelae are associated with RF?

A

Heart valve damage

Infectious endocarditis

43
Q

What is the most likely diagnosis for a pt with a recent viral URI, an arrythmia, pericardial friction rub, and elevated myocardial enzymes?

A

Pericarditis

44
Q

What is the most likely causative org of pericarditis?

A

Cox A or B

Echo or influenza too

45
Q

What tests should be performed for a definitive diagnosis?

A

RT-PCR

46
Q

What is the proper course of tx for this infection?

A

Supportive (if viral origin)

CRAAB 1 (11 decks)

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