Microbio Flashcards

1
Q

What two diseases are caused by BK viruses in the immunocompromised?

A
  1. nephropathy (esp. post-transplant)

2. hemorrhagic cystitis

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2
Q

What three antibiotics disrupt peptidoglcan?

A

Vancomycin, cephalosporins, penicillins

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3
Q

What is azithromycin?

A

a macrolide

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4
Q

Which bacteria has a capsule made of polyribosylribitol phosphate (PRP)?

A

H. flu

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5
Q

Match the description with the opportunistic fungi:

  1. Psuedohyphae, germ tubes at 37 degrees C
  2. Septate hyphae that branch at 45 degree angle
  3. Wide capsular halos and unequal budding
  4. Irregular, broad, nonseptate hyphae branching at wide angles
A
  1. candida albicans
  2. aspergillus fumigatus
  3. cryptococcus neoformans
  4. mucor
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6
Q

Where does S. aureus live on the body?

A

25-30% of people have it in their nose, especially the anterior nares (this applies to both MRSA and non-MRSA)

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7
Q

Explain why anemia accompanies a mycoplasma infection:

A

shares antigens w/ human erythrocytes → cold agglutinating hemolytic anemia

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8
Q

What kind of virus typically generates a polyprotein that must be cleaved into final protein products?

A

Linear, positive-sense, non-segmented ssRNA (eg. Picornaviruses s.a. echo)

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9
Q

What is granulomatous disease? What organisms is a patient with CGD susceptible to?

A
Defect of NADPH oxidase →  ↓ ROS/absent respiratory burst in neutrophils → susceptibility to catalase + organisms (PLACESS)
- Pseudomonas
- Listeria
- Aspergillus
- Candida
- E. coli
- S. aureus
- Serratia
(- Nocardia)
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10
Q

3 organisms which have polysaccharide vaccines available?

A
  1. Streptococcus pneumonia
  2. Neisseria meningitidis
  3. Haemophilus influenza
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11
Q

Describe the resistance mechanisms in MRSA

A

S. aureus that has penicillinase → not susceptible to most penicillins → if additionally has altered binding proteins → resistant to penicillinase-stable penicillins: methicillin, oxacillin, nafcillin

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12
Q

What are the two classes of Group D strep and when would each cause a problem?

A
  1. Growth in bile and 6.5% NaCl:
    Enterococci and E. faecium
    - seen in endocarditis after GU procedures
  2. Growth in bile but not 6.5% NaCl:
    Nonenterococci, S. bovis
    - seen in endocarditis assoc. w/ colon cancer
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13
Q

What conditions are usually present that –> S. viridans endocarditis?

A

abnormal heart valve already present + dental extraction

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14
Q

What does exotoxin A of diptheria do?

A

transfers a ribose residue from NAD to histidine on EF2 (i.e. ribosylates EF2) → inactivates EF2 → inhibits protein synth → cell death

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15
Q

What toxin is released by C. perfringens?

A

lecithinase (aka phospholipase C aka C. perfringens alpha toxin) → degrades membrane phospholipids → cell membrane destruction → cell death → gas gangrene

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16
Q

What test would you use to confirm Staph epidermidis?

A
  1. Catalase (negative → staph; positive → strep)

2. Coagulase (negative → epidermidis or other; positive → aureus)

17
Q

What causes the cardiomyopathy and neuropathy in diptheria?

A

diptheriae exotoxin in blood stream deactivates EF-2 → inhibits elongation of protein on ribosome → inhibited protein synthesis

18
Q

What gram positive cocci synthesize dextrans from glucose?

A

Strep. viridans (the extracellular dextran is thought to help it colonize host surfaces)

19
Q

How long does it take for acute rheumatic fever to develop? Sydenham chorea? Rheumatic heart disease?

A

10d - 6wk: main symptoms include pancarditis and migratory polyarthritis
2-3 mo: Sydenham chorea
10-20 yr: Rheumatic HD

20
Q

How can you distinguish EHEC (0157:H7) from other forms of E. coli in the lab? What is its toxin and mechanism of action?

A

does not ferment sorbitol (containing MacConkey agar) or produce glucuronidase; produces Shiga-like toxin which inactivates the 60S ribosomal subunit

21
Q

Is the shiga-toxin or invasion by shigella more important in the disease state caused by shigella infection?

A

invasion - strains that don’t produce the toxin have been found to cause significant disease

22
Q

Does staph aureus cause GI absesses?

A

Not typically, it causes skin abscesses

23
Q

What does hep D need from Hep B to become infectious?

A

coating (of HDAg) by HBsAg

24
Q

Infection whose lab finding is ↓ Na+?

A

legionella

25
Q

Which cephalosporin is useful for pseudomonas?

A

Cefepime - 4th generation
Ceftazidime - 3rd generation
Note: ceftriaxone does not cover pseudomonas