Antibacterial and antifungal agents Flashcards Preview

Clinical pathology > Antibacterial and antifungal agents > Flashcards

Flashcards in Antibacterial and antifungal agents Deck (33)
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1
Q

Bacteria features

A
  • Prokaryotes
  • DNA ring like in cytoplasm
  • uniform simple structures
2
Q

Fungi features

A

Eukaryotes

  • DNA separated from cytoplasm by nuclear membrane
  • Hyphae, spores
  • Complex structures
3
Q

What features do bacteria and fungi share

A

Both have:

  • Cell wall
  • Cell membrane
  • DNA
  • Synthetic functions (protein synthesis)
4
Q

What are antibiotics

A

Chemical products of microbes that inhibit or kill other organisms

5
Q

Bacteriostatic/ fungistatic

A

Inhibit growth - protein synthesis inhibitors

6
Q

Bactericidal/ fungicidal

A

Kill organism - cell-wall active agents

7
Q

Minimum inhibitory concentration (MIC)

A

minimum concentration at which visible growth is inhibited

8
Q

synergism

A

activity of 2 antimicrobials given together is greater than the sum of their activity if given separately

9
Q

Antagonism

A

one agent diminishes the activity of the other

10
Q

Antimicrobial targets

A
  • Cell wall
  • Protein synthesis
  • DNA synthesis
  • RNA synthesis
  • Cell membrane
11
Q

Bacterial cell wall

A
  • Peptidoglycan
  • Gram +/- bacteria
  • Polymer of glucose derivatives
12
Q

Fungi cell wall

A
  • β-1,3-glucan

- Forms fibrous network on inner surface of the cell wall

13
Q

β-lactams

A
  • Cell wall synthesis inhibitor
  • Targets Transpeptidase enzymes involved in cross-linking the cell wall of bacteria
  • β-lactamase enzymes hydrolyse inactive β-lactams
14
Q

Examples of B lactams

A
  • Penicillins
  • Cephalosporins - cefuroxime
  • Carbapenems -meropenem
  • Monobactams - GRAM - only
15
Q

Glycopeptides

A
  • Large molecules that inhibit binding of transpeptidases
  • Used to treat MRSA
  • E.g vancomycin, tigecycline
16
Q

Antifungal cell wall synthesis inhibitor

A
  • Inhibit β-1,3-glucan synthase
  • Echinocandins
  • anidulafungin, caspofungin
17
Q

Bacteria protein synthesis inhibitors function

A
  • Affects the ribonucleoprotein complexes

- Initiation of synthesis happens after 50s and 30s subunits combine - work on these

18
Q

Bacteria protein synthesis inhibitors

A
  • Aminoglycosides
  • MLS antibiotics
  • Tetracyclines
  • Oxazolidinones
  • Mupirocin
  • Fusidic acid
19
Q

Aminoglycosides

A

Gentamicin - binds to 30s ribosomal subunit

20
Q

MLS antibiotics

A
  • Macrolides, Lincosamides, Streptogramins
  • Macrolides - Clarithromycin
  • Lincosamides - Clindamycin for strep
21
Q

Tetracyclines

A
  • Doxycycline for MRSA

- Binds to 30s and inhibits translation

22
Q

Oxazolidinones

A
  • Linezolid

- Inhibits initiation of protein synthesis binds to 50s

23
Q

Why can antifungals not target protein synthesis

A

Fungi share the same mechanism of protein synthesis to humans

24
Q

Bacterial DNA synthesis inhibitors

A
  • Trimethoprim
  • Sulphonamides
  • Quinolones and Fluoroquinolones
25
Q

Trimethoprim

A
  • Inhibits folate synthesis - Targets dihydrofolate reductase
  • Used for UTI’s
26
Q

Sulphonamides

A
  • Inhibits folate synthesis
  • Co-trimoxazole
  • Targets dihydropteroate synthetase
27
Q

Quinolones and Fluoroquinolones

A
  • Inhibit DNA gyrase + topoisomerase IV

- Nalidixic acid effective against bacteria

28
Q

Fungal DNA synthesis inhibitors

A
  • 5 Fluorocytosine

- selective toxicity is poor

29
Q

Bacteria RNA synthesis

A
  • Rifamycin e.g. rifampicin: RNA polymerase inhibitor, Prevents synthesis of mRNA
30
Q

Bacterial cell membrane targeters

A
  • Colistin

- Daptomycin - destroys outer membrane

31
Q

Fungal cell membrane targeters

A
  • Azoles - oral thrush
  • Terbinafine - treats athletes foot
  • Amphotericin B - Binds to ergosterol causing physical damage to the membrane. Forces holes in the fungal cell membranes
32
Q

Antimicrobial combination therapy

A
  • provides broad spectrum
  • Increase efficacy - synergistic combos
  • Reduce resistance
33
Q

Fidaxomicin

A

new antibiotic for C.diff

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