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FRACP > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

What is Reye’s syndrome?

A

Reye’s syndrome is a post viral reaction to aspirin that manifests as confusion and fatty liver changes in young adolescents.

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2
Q

What serious condition does Shigella-toxin E. coli (STEC) cause? What effect does giving ABx do to the risk of this occurring?

A

Shigella-toxin E. coli (STEC) may cause HUS, giving Abx may increase the risk to 50%.

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3
Q

What are the ESCAPPM organisms? What is their peculiarity?

A

ESCAPPM organisms: enterobacter, serratia, citrobacter, aeromonas, proteus, provedincia, morganella

All ESCAPPM organisms have inducible beta-lactamase activity that is chromosomally mediated which increases likelihood of cephalosporin resistance.

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4
Q

What is the MOA of aciclovir?

A

MOA of acyclovir: analogue of deoxyguanosine that halts DNA production e.g. HSV replication.

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5
Q

Which antibiotic should and should not be used against ESCAPPM organisms?

A

Regarding the ESCAPPM organisms:

Cephalosporins should NOT be used

Antibiotics that should be used:
1st line: penicillin and aminoglycosides
2nd line: carbapenems or quinolones

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6
Q

Which populations are at risk of varicella-zoster pneumonitis?

A

Not children.

At-risk (SIP): smokers, immunosuppressed, pregnant.

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7
Q

What 2 conditions can VZV cause and where does it lie dormant in the body?

A

VZV causes herpes zoster (shingles) and chicken pox.

VZV lies dormant in the DRG.

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8
Q

What is the treatment of VZV?

A

acyclovir / valaciclovir / famciclovir

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9
Q

What is the likely food-borne pathogen in the following foods:

  1. Chicken
  2. Fried rice
  3. Raw eggs
  4. Raw oysters
  5. Soft cheese/Raw milk
  6. Home packaged food / honey
  7. Cream-filled pastry / Deserts
A
  1. Chicken: campylobacter, salmonella,
  2. Fried rice: bacillus cereus
  3. Raw eggs: salmonella
  4. Raw oysters (VNS): vibrio, norovirus, shigella
  5. Soft cheese/Raw milk (CLEY): campylobacter, listeria, e. coli (pathogenic), yersinia
  6. Home packaged food / honey: clostridium botulinum
  7. Cream-filled pastry / Deserts: staphylococcus aureus
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10
Q

What is Corynebacterium diphtheria?

A

Corynebacterium diptheria is a gram positive faculative anaerobe with 3 strains:

  1. Gravis
  2. Intermedius (most toxic)
  3. Mitis
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11
Q

Immunocompromised patient is noted to have multiple ring-enhancing lesions on CT/MRI of the brain. What is the pathogen? How is it treated?

A

Toxoplasma gondii

Empirical Rx:

metronidazole + cephalosporin (ceftriaxone/cefotaxime)

Targeted Rx:

pyrimethamine + sulphonamide

+/- leucovorin to prevent pyrimethamine-induced haematologic toxicity

or Bactrim (trimethoprim-sulfamethoxazole) if patient with sulphur allergy

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12
Q

Which pathogen is suggested by a positive antistreptolysin O antibody?

A

Group A streptococci (GAS).

ASOT (antistreptolysin O titre) = blood test

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13
Q

What 3 conditions might Group A streptococci (GAS)?

A
  1. Post-streptococcal glomerulonephritis - mild AKI to severe nephritic syndrome
  2. Tonsillar-pharyngitis +/- delayed:
    a. scarlet fever (strep. pyogenes) - sandpaper rash
    b. acute rheumatic fever (arthritis/carditis/chorea)
  3. Streptococcal toxic shock syndrome
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14
Q

What is significance of the M-protein in virulence of Group A streptococci (GAS)?

A

M-protein is encoded by the emm gene.

Protects the organism against humoral surveillance and phagocytosis by polymorphonuclear leukocytes.

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15
Q

Which Abx is used for Group A streptococci (GAS)?

A

Penicillin V (phenoxymethylpenicllin)

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16
Q

What are IV and PO antibiotics that treat MRSA?

A

IV:
clindamycin OR vancomycin

PO:
clindamycin OR doxycycline OR trimethorpim

If resistant to ALL of these then consider

rifampicin + fusidic acid

17
Q

How do beta-lactam antibiotics work?

Organism develop resistance with beta-lactamase, how might this resistance be obviated?

A

Inhibit cell wall biosynthesis

Clavulonic acid is often given intercurrently to inhibit beta-lacatamase activity.

18
Q

MOA of macrolide antibiotics (Erythromycin, Azithromycin, Clarithromycin, Roxithromycin)?

A

‘macrolides are from the 1950s’

Block protein synthesis by binding to the 50S ribosomal unit.

19
Q

MOA of sulphonamide (trimethoprim/bactrim)

A

sulFOnamides inhibit FOlic acid synthesis

20
Q

MOA of aminoglycosides (gentamicin, streptomycin)?

A

‘a young guy in his 30s is now deaf cos he was given gentamicin - tragic!’

Block protein synthesis by binding to the 30S ribsomal subunit.

21
Q

MOA of Quinolones / Fluoroquinolones (Ciprofloxacin, Norfloxacin, Moxifloxacin)?

A

‘people who wear FLUOR like to GYRATE TOPless in discos’

Inhibition of DNA gyrase / DNA to topoisomerases

22
Q

Which pathogen is cutaneous anthrax due to?

A

Gram positive rod - Bacillus anthracis

Contracted by direct contact with bacteria

23
Q

What are the clinical features of cutaneous anthrax (3)?

A

Black eschar
No pus
Painless with widespread oedema

24
Q

True/False: cutaneous anthrax treated with antibiotics has a lower mortality that pulmonary anthrax.

A

True.

25
Q

What type of food is E. Coli 0157:H7 most often found in? How might transmission be reduced?

What condition might it cause?

Which antibiotic should be used?

A

Meat (beef) - reduce transmission by thoroughly cooking the meat.

May cause HUS: bloody diarrhoea and renal impairment.

Do not treat with antibiotics (increased HUS risk by 50%)

26
Q

GIven CSF results how do you differentiate:

  1. Bacterial
  2. Viral
  3. TB
A
  1. Bacterial:
    Glucose: low (less than 1/2 plasma BSL)
    Protein: high ( > 1.0g/L)
    WCC: up to 5000 PMN
  2. Viral:
    Glucose: normal
    Protein: high / normal
    WCC: up to 1000 Lc
  3. TB (same as bacterial, except with Lc)
    Glucose: low
    Protein: high ( > 1.0 g/L)
    WCC: up to 1000 Lc
27
Q

What is hypervirulent strain Clostridium Difficile?

What antibiotic is used to treat it?

A

Clostridium Difficile (aka NAP-1/027 strain) has increased production of toxin A and B (20x) due to mutated TCDC (The C. Diff Crazy) gene.

Due to exposure to fluoroquinolones (15x risk) but may be other too (cephalosporins and macrolides)

Treated with metronidazole / vancomycin (severe cases)

28
Q

Compare anaerobes E.Coli to C.Diff in terms of bacterial morphology.

A

E. Coli is a gram NEGATIVE rod

C. Diff is a gram POSITIVE rod (that forms spores)

29
Q

Patient with hypervirulent C. Difficile suddenly stopd having diarrhoea. Is this a good thing?

A

No.

Likely ileus with risk of toxic megacolon / perforation.

30
Q

A patient with hypervirulent C. Difficile is refractory to treatment with metronidazole and vancomycin regimens. What other options are there?

A
  1. Rifaximin and PO vancomycin
  2. Fidaxomicin (non-absorbed ABx) - better than vancomycin (very expensive)
  3. Faecal transplant

FRACP (20 decks)

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