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Phase 3 > Week 6 - Clinical Microbiology and Infection 1 > Flashcards

Week 6 - Clinical Microbiology and Infection 1 Flashcards

1
Q

What are the main infective causes of death in low-income countries?

A 
Lower RTI
HIV/AIDS
Diarrhoeal diseases 
Malaria
TB
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2
Q

What are the main infective causes of death in high-income countries?

A

Lower RTI

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3
Q

Reasons for increasing infection rate worldwide?

A

New methods of travel (air) and trade (food)
Overuse of antibiotics
Population at extremes of age
Development in medical intervention/technology
Development of agriculture/ animal husbandry
Sexual behaviour
Breakdown of social/ economic/ political systems

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4
Q

8 resistance mechanisms in gram -ve bacteria

A

1) Loss of porins
2) Over-expression of transmembrane efflux pumps
3) Beta-lactamases in periplasmic space
4) Antibiotic modifying enzymes
5) Target mutation of DNA
6) Ribosomal mutation to alter protein synthesis
7) Mutation of lipopolysaccharide structure
8) Bypass of target

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5
Q

How was Exserohilum rostratum (fungus) epidemic caused?

A

By contaminated steroid vials

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6
Q

What stain is used to stain bacteria?

What colours do gram positive and negative bacteria stain?

A 
Crystal violet
Positive = blue/purple
Negative = pink
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7
Q

Why do bacteria stain differently with crystal violet?

A

Gram positive bacteria have a thicker peptidoglycan cell wall so retain the stain more than gram negative bacteria and become darker purple

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8
Q

Which type (+ or -) of bacteria has greater protection against antibiotics and why?

A

Gram negative - it has a 2nd outer membrane which gram positive don’t have, which allows them to regulate more what passes in/out of cell

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9
Q

What are bactericidal antibiotics?

A

Directly kill bacteria

But can cause release of toxins and inflammatory material

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10
Q

What are bacteriostatic antibiotics?

A

Suppress growth, but do not directly kill

Require additional factors to kill the bacteria

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11
Q

What are the 5 main gram -ve bacteria?

A 
Neisseria
Haemophilus
E. Coli
Pseudomonas
Other coliforms
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12
Q

What are the 3 main gram +ve bacteria?

A

Streptococcus
Staphylococcus
Enterococcus

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13
Q

What are the 2 main gram anaerobic bacteria?

A

Bacterioides (-ve)

Clostridium (+ve)

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14
Q

Describe the 3 main methods of antibiotic therapy

A

Guided - give narrow spectrum agent when cause of infection can be identified

Empirical - give broad spectrum where cause of infection cannot be identified

Prophylactic - give to prevent infection before it begins

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15
Q

What infection type is use of antibiotics associated with?

A

C. Difficile

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16
Q

What are the aims of guided antibiotic therapy?

A

Use antibiotic which has limited action to the bacteria causing infection 

If possible limit penetration to site of infection 


Achieve clinical cure with as little impact on colonisation and resistance as possible 


Narrow Spectrum

17
Q

What are the 4 classes of Beta-lactam antibiotics?

Give the required examples of each

A

Penicillins (benzylpenicillin, amoxicillin, flucloxacillin)

Cephalosporins (ceftriaxone)

Carbapenems
(Meropenem)

Monobactams
(Aztreonam)

18
Q

What are the 2 main beta-lactam/ beta-lactamase inhibitor combination therapies?

A

Co-amoxiclav (Augmentin) - Amoxicillin + clavulanic acid

Tazocin - Piperacillin + tazobactam

19
Q

What is the MOA of beta-lactams?

A

Inhibits cross linking of peptidoglycan, causing lysis of bacteria (bactericidal)

20
Q

What is the function of beta-lactamase?

A

Lyse and inactivate beta-lactam drugsby disrupting the beta-lactam ring

21
Q

What bacteria secrete beta-lactamase?

A

Gram negatives and Staph aureus

22
Q

What route are most beta-lactams given and why?

A

IV - most poorly absorbed orally (except amox, fluclox)

23
Q

How are beta-lactams daily excreted?

A

Unchanged in urine, and some in bile

24
Q

How are beta-lactams distributed around the body?

A

Can reach hard to reach places and are effectively distributed

25
Q

What are the main adverse effects of beta-lactams?

A

SomGI toxicity:

  • N/V
  • Diarrhoea
  • Cholecystitis

Hypersensitivity:

  • 1) Anaphylaxis, urticaria
  • 4) Dermatology (?with systemic upset)
  • Interstitial nephritis (1/4)

Infection:

  • Thrush (oral/ genital)
  • C. DIff
  • Resistance bacterial strains

Other:

  • Seizure
  • Haemolysis
  • Leukopenia
26
Q

Is it possible for penicillin allergic patients to be managed safely with other beta-lactams?

A

Sometimes - particularly with Aztreonam (Monobactam), providing the patient doesn’t have anaphylactic reaction to penicillin

27
Q

Benzylpenicillin route and use

A 
IV (oral uncommon = penicillin V)
Serious strep (and staph)
28
Q

Amoxicillin route and use

A

Oral/IV

Strep and enterococcus - Resp tract infections

29
Q

Flucloxicillin route and use

A

Oral (but nausea)/IV

Staph (and strep) - common causes of cellulitis

30
Q

Co-amoxiclav use

A

Everything except Pseudomonas

31
Q

Tazocin use

A

Everything

32
Q

Meropenem use

A

Everything

33
Q

Ceftriaxone use

A

All except Pseudomonas and Enterococcus

Less susceptible to beta-lactamase

34
Q

Azetreonam route and use

A

IV only

Gram -ves only (not bacterioides)

35
Q

Vancomycin route and use

A

IV mainly / Oral for C. Diff only
Mainly MRSA
All gram +ve

36
Q

What are the main side effects of vancomycin

A 
Nephrotoxicity - if dose too high
Ototoxicity - if dose too high
Anaphylactoid reactionn ("Red-Man Syndrome) - if given too fast
37
Q

Why are beta-lactams the best antibiotic class?

A

Excellent efficacy and low toxicity

Wide spectrum of activity

Phase 3 (4 decks)

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