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Infection > Session 4- antimicrobials > Flashcards

Session 4- antimicrobials Flashcards

1
Q

What is a protozoa?

A

Single celled eukaryote

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2
Q

Types of antimicrobial

A

Antibacterials
Antifungals
Antiprotozoals
Antivirals

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3
Q

How can you classify antibacterials?

A

By their

  • mechanism of action
  • spectrum (broad/narrow)
  • chemical structure
  • kill/ inhibit growth and replication (bacteriostatic vs bactericidal)
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4
Q

3 ways of measuring antibiotic activity

Explain each

A
  • Disc sensitivity
  • MIC, broth microdilution
  • MIC, E test (slow)

Disc loaded with antibiotic is placed in on an inoculated agar plate and the zone of inhibition/ clearance measured. (Larger diameter= more antibiotic inhibition).

Minimum inhibitory concentration. Concentration of antibiotic is doubled each time until no bacterial growth occurs.

E- test; strip contains an antibiotic gradient and is placed on an inoculated agar. Circumference of zone of clearance begins from the MIC

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5
Q

Which 3 types of antibiotic inhibit protein synthesis?

Give an example of each

A
  • Tetracyclines (doxycycline)
  • Aminoglycosides (Gentamicin)
  • Macrolides (erythromycin)
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6
Q 
Tetracyclines: 
Mechanism 
Use
Adverse effects 
Example
A

Inhibit protein synthesis
Used as an alternative to penicillin in gram positive infection
Causes staining to developing teeth so no children < 12 or pregnant women
E.g. Doxycycline

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7
Q 
Gentamicin:
Type of antibiotic
Mechanism 
Use 
Adverse effects
A

Aminoglycoside
Inhibits protein synthesis

Endocarditis
Severe gram negative sepsis

Can be nephrotoxic and ototoxic

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8
Q

Erthromycin:
Type of antibiotic
Mechanism
Use

A

Macrolide
Inhibits protein synthesis
Alternative to penicillin against gram positive infection

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9
Q

Two types of antibiotic which inhibit cell wall synthesis?

Examples

A
  • Beta lactams;
    Penicillins (flucloxacillin)
    Cephalosporins (ceftriaxone)
    Carbapenems
  • Glycopeptides (vancomycin)
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10
Q

Antibiotics used for meningitis and why?

A

Empirical ceftriaxone
Penicillin G/ Ampicillin
Bc both pass inflamed BBB and have action in CSF

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11
Q

What does flucloxacillin treat?

A

Cellulitis- caused by Staphylococcus Aureus/ Streptococcus Pyogenes

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12
Q

Penicillin is mainly active against ___?

A

Gram positives-
Staphylococcus
Streptococcus (especially)

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13
Q

Carbapenems:

Type of antibiotic
Mechanism
Use
Example

A
  • Beta lactams (others are penicillins and cephalosporins)
  • Inhibits cell wall synthesis
  • Reserve for gram negative infections (+ penicillin allergy)
  • imipenem
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14
Q

Vancomycin:

Type of antibiotic
Mechanism
Use
Features

A
  • Glycopeptide
  • Inhibits protein synthesis (along with tetracyclines and macrolides)
  • MRSA & serious C .difficile (oral). Gram positives.
  • Poor oral absorption so use IV or IM usually. Narrow therapeutic index so needs TDM, therapeutic drug monitoring.
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15
Q

Is clostridium difficile gram positive or negative?

A

Gram positive and spore-forming

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16
Q

Antibiotics which inhibit nucleic acid synthesis? (3)

How do they do this?

A
  • Quinolones (Ciprofloxacin)
    Inhibit DNA gyrase (relaxes the supercoil in transcription)
  • Rifampicin
    Inhibits bacterial RNA polymerase
  • Trimethoprim (UTI) + Sulphonamides
    Inhibit folate synthesis
17
Q

Quinolones:

Mechanism
Use
Adverse effects
Example

A
  • Inhibit nucleic acid synthesis (through inhibition of DNA gyrase)
  • Against gram negatives
  • Aortic dissection, tendinitis and rupture, plus CNS effects
  • ciprofloxacin
18
Q

What do Azoles and Polyenes do?

Examples

A

Antifungals (fungistatic)
Azoles inhibit cell membrane synthesis
Polyenes inhibit CM function

- Azoles 
fluconazole (candida)
itraconazole (aspergillus)
- Polyenes 
nyastatin (topical for candida)
Amphoteracin (IV systemic fungal infection- aspergillus)
19
Q

Antifungals for aspergillus?

A

Itraconazole (azole)

I.V. Amphoteracin if systemic (type of polyene)

20
Q

Acyclovir:

What is it?
Mechanism
Uses

A

Anti viral agent
Prevents DNA synthesis (inhibition of DNA polymerase when phosphorylated)

Varicella zoster virus- Chicken pox, shingles,

Herpes simplex virus- genital herpes, encephalitis

21
Q

What is encephalitis?

Which infection causes it?

A

Inflammation of the brain caused by Herpes Simplex virus

22
Q

What does Varicella Zoster virus cause?

Medication?

A

Chicken pox and shingles

Acyclovir

23
Q

What does Herpes Simplex virus cause?

A

Genital warts and encephalitis

24
Q

Tamiflu;

What is it?
Mechanism
Uses

A

Also know as oseltamivir, it’s an antiviral agent
Inhibits viral neuraminidase in flu so the newly formed virions cannot be released into the blood stream (viral replication stops)
Influenza A and B

25
Q

What does neuraminidase enzyme do?

A

Cleaves the sialic acid residues to break the glycosidic linkage between the new virion and host cell enabling release into the blood stream (to further infect cells)

26
Q

What’s special about metronidazole?

A

It’s antibacterial (anerobic bacteria) AND antiprotozoal (eukaryotic)

27
Q

Amoebae
Giardia
Trichomonas
are all types of what?

What can you treat them with?

A

Protozoa
G and T are parasites

Metronidazole

28
Q

Amoebae
Giardia
Trichomonas
What do they cause?

A

Dysentery (inflammation of intestines causing bloody diarrhoea)

Diarrhoea

Vaginitis / trichomoniasis (STI)

29
Q

Use of trimethoprim

A

UTI

30
Q

How do sulfonamides work?

How does trimethoprim work?

A

Sulfonamides inhibit de novo synthesis of folate in bacteria
Trimethoprim inhibits conversion of dihydrofolate (DHF) to tetrahydrofolate (THF) in bacterial but not human cells.

31
Q

Why do we need folate?

A

To synthesise DNA nucleotides we (and bacteria) require enzymes which use co-factors deriving from folate.
Specifically the derivative THF, tetrahydrofolate, is critical to enzyme activity

32
Q

List some mechanisms of bacterial antibiotic resistance

A

Reduced uptake
Mutation of target site
Down regulating expression of target site
Increased efflux
Enzymes which inactive the drug. E.g. beta lactamases inhibit beta lacta drugs

33
Q

Types of bacterial resistance? (3)

A

Innate
Acquired- gain new DNA, usually permanent
Adaptive- response to a stress like sub-inhibitory level of antibiotic; can be reversible

34
Q

Protective mechanisms against infections in the lungs? (Innate immunity)

A

Mucociliary clearance
Coughing
IgA (immunogolbulin of mucous membranes)
Alveolar macrophages

Antimicrobial proteins;

  • lysozyme (breaks bacterial cell walls)
  • lactoferrin (bacteriocidal; associated with mucus)
35
Q

Dyspnea?

A

Shortness of breath

36
Q

What is co-amoxiclav?

When is it used?

A

Combination drug which includes a beta lactam drug (amoxicillin) and a beta lactamase inhibitor

  • In community acquired pneumonia when the bacteria is resistant to amoxicillin (produce beta lactamases). E.g. Haemophilus Influenzae.
  • Or in severe pneumonia caused by Streptococcus Pneumoniae.

Infection (14 decks)

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