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CRRAB Week 3 > Microbiology Cases for Midterm > Flashcards

Microbiology Cases for Midterm Flashcards

1
Q

What is the significance of M protein?

A

Protein that is harmful in untreated streptococcal pharyngitis.

  • Patients can develop a cross-reactive antibody against heart tissue (meromyosin).
  • Glomerulonephritis of IE –> can come from pharyngitis or skin infections
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2
Q

What is a typical course of untreated Rheumatic Heart Disease?

A
  1. Exposure to group A streptococcus
  2. Group A streptococcal upper respiratory tract infection
  3. Acute rheumatic fever (flu-like)
  4. Recurrent acute rheumatic fever
  5. Rheumatic heart disease (RHD)
  6. Can lead to heart failure or stroke endocarditis –> surgery/disability/death
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3
Q

What are the vascular phenomena classified by the Duke Criteria?

A
  • Arterial emboli
  • Janeway lesions
  • -Usually non-tender, small hemorrhagic lesions on palms and soles
  • -Last days to weeks
  • -Commonly seen in acute IE
  • -Histology consistent with septic micro-emboli (bacteria in lesion)
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4
Q

What are the immunological phenomena classified by the Duke Criteria?

A
  • Rheumatoid factor
  • Roth’s spots
  • Osler’s nodes
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5
Q

What is rheumatoid factor?

A
  • Antibody that can bind the constant region of IgG.
  • Antibody against antibody that leads to immune complexes, deposition, inflamed joints, etc.
  • Antibody against antibody–binds Fc portion of IgG antibody
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6
Q

What are osler’s nodes?

A
  • Red-purple, tender, slightly raised lumps with pale center on pads of fingers and toes
  • Pain precedes development of lesion (~24 hrs)
  • Stays for hours-days
  • Can occur at any time with endocarditis
  • Immunological cause (inflam.) but bacteria also isolated from lesions (early on)
  • Type II hypersensitivity!! (cytotoxic- antibody mediated)
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7
Q

What is an example of Type II hypersensitivity?

A

RHD - antibodies bind to M protein on the tissue but then start to confuse the M protein for meromyosin in the heart tissue. Then the antibodies start attacking meromyosin.

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8
Q

What are the three mechanisms of Type II hypersensitivity?

A
  1. Opsonization and phagocytosis
  2. Complement-and Fc receptor-mediated inflammation
  3. Antibody-mediated cellular dysfunction
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9
Q

What happens in Type II hypersensitivity?

A

Cytotoxic - IgM and IgG bind to fixed antigen on “enemy” cell –> cellular destruction

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10
Q

What are examples of Type III hypersensitivity?

A

Roths spots

Osler nodes

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11
Q

What is type III hypersensitivity?

A

Immune complexes - antigen-antibody (IgG) complexes activate complement, which attracts neutrophils, neutrophils release lysosomal enzymes
(antigen-antibody-complement)

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12
Q

What infections lead to hemolytic anemia?

A 
CMV
EBV
Malaria
Hepatitis
Streptococcal infections
Typhoid fever
etc.
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13
Q

How can you get anemia in acute and subacute endocarditis?

A

Clots on the heart disrupt and destroy RBCs passing through.
-Probably causes spherocytes

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14
Q

What are the most important virulence factors in CV disease?

A

Factors used for attachment!

Being able to establish infection on heart tissue is KEY.

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15
Q

What are 2nd most important virulence factors in CV disease?

A

Factors involved in invasion and multiplication

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16
Q

What VF are associated with Streptococcus species (viridians)?

A
  • Dextran production/glycocalyx formation
  • Surface adhesion proteins (FimA, GspB)
  • these help it adhere to valve and colonize
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17
Q

What VF are associated with Streptococcus pneumoniae?

A

Capsule

-Helps it evade host defenses and neutralize the ability of antibodies to attach to bacteria

18
Q

What VF are associated with Streptococcus pyogenes?

A

Capsule
-Helps it evade host defenses and neutralize the ability of antibodies to attach to bacteria
M Protein

19
Q

What VF are associated with Neisseria meningitidis?

A

Capsule

-Helps it evade host defenses and neutralize the ability of antibodies to attach to bacteria

20
Q

What VF is associated with Enterococcus species?

A

Biofilm formation (various proteins)

21
Q

What VF are associated with Staph. aureus?

A
  • Capsule
  • Biofilm formation (various proteins)
  • Elastin, Collagen, & Fibronectin (FnbpA) binding proteins*
  • Coagulase
  • Leukocidin
22
Q

What VF are associated with Staph. epidermis?

A
  • SD-repeat containing protein-G (SdrG)*

- Biofilm formation (various proteins)

23
Q

What virulence factors are associated with Coxsackie A, Coxsackie B and Adenovirus?

A

Coxsackie-Adenovirus cellular receptor (CAR) binding proteins

24
Q

What is the significance of CAR binding proteins?

A

They are cellular receptors that allow COXA, COXB, and adenovirus to bind directly to heart tissue!

25
Q

What VF are associated with Rickettsia rickettsia?

A
  • OmpA and OmpB (attachment)

- Type 4 Secretion System (T4SS) (host cell entry)

26
Q

What is the T4SS?

A

Type 4 Secretion System:

  • Look like needle in syringe
  • Helps it to deposit stuff into the cell
  • Can induce the cell to do something for it
  • Once Rickettsia binds to a cell it injects molecules that tricks the host cell into engulfing it
  • Then it can infect the host cell
27
Q

What type of pathogen is Rickettsia?

A

Obligate intracellular pathogen that requires host cell machinery!

28
Q

What is the name for the wide variety of attachment proteins used by strep and staph to form infections?

A

MSCRAMMs:

Microbial Surface Components Recognizing adhesive matrix molecules

29
Q

What is likely sufficient to diagnose RMSF?

A

Clinical diagnosis - classic triad: fever, headache, rash

30
Q

How to diagnose RMSF with tests?

A
  • Indirect immunological assay (fluorescence/agglutination)
  • Skin biopsy
  • PCR for R. Rickettsii DNA
31
Q

What is used to treat RMSF?

A

Doxycycline

32
Q

What can you use to diagnose Coxsackievirus A or B or Echovirus infection?

A

RT-PCR

33
Q

How do you treat a viral pericarditis?

A

Give supportive treatment

34
Q 
Fever 104F
Chills
Severe headache
Muscle aches
Pulse = 110 bpm
Resp. Rate = 28 bpm
BP = 100/60 mmHg
Rash - palms and soles, extremities
What does he have?
How to confirm?
A 
RIckettsia Rickettsii - RMSF
-Indirect immunological assay 
-Skin biopsy
-PCR for RR DNA
Clinical diagnosis: classic triad
35
Q

What infectious microorganisms cause rash on palms of hands and soles of feat?

A
  • Syphyllus
  • Rickettsia Rickettsii
  • Coxsackie Viruses
  • T. pallidum
36
Q

-102.2F
-11 yr old
-Joint pain, swelling
-SOB upon exertion & laying down
-Sore throat improved with penicillin G four weeks ago
-HR: 160 bpm
-RR: 32 bpm
-BP: 100/60 mmHg
-O2: 94%
-Holosystolic murmur 3/6 heard at apex with radiation to axilla
-Cardiomegaly on X-ray
-EKG = prolonged PR interval
What does he have? What organism caused it?

A

Rheumatic fever

Streptococcus pyogenes

37
Q

What will follow a rheumatic fever infection in genetically predisposed individuals?

A

RHD - Type II hypersensitivity with M protein

38
Q

-Summer!
-Severe chest pain
-Arrhythmias
-104F
-Extreme fatigue
What inf. agents? What does he have?

A

Coxsackievirus A or B, Echovirus, Pericarditis

39
Q

How do infectious agents reach the heart?

A
  • Oral cavity
  • Skin
  • Upper respiratory tract
40
Q

Why does endocardium become enflamed in endocarditis?

A

Immune response to the valve colonization

CRRAB Week 3 (12 decks)

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