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Human Diseases > Mechanism of action of antibiotics (Antibacterial agents) > Flashcards

Mechanism of action of antibiotics (Antibacterial agents) Flashcards

1
Q

How can antibiotics be classified?

A

Bactericidal, Bacteriastatic, Bacteriolytic

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2
Q

Bactericidal definition

A

Kill the bacteria

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3
Q

Bacteriostatic definition?

A

Inhibit or retard bacteria growth and multiplication

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4
Q

Minimum inhibitory concentration defintion?

A

Lowest concentration of an antimicrobial that will inhibit the visible growth of a micro-organism

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5
Q

Minimum bactericidal concentration?

A

Lowest concentration fo an anti-microbial required to kill a micro-organism

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6
Q

How can bacteria be classified?

A

gram staining, aerobic, aerobic

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7
Q

List differences between G+ve and G-ve cells?

A

+ve have 1 cell membrane with a thick cell wall on the outside made with lots of peptidoglycan
-ve have 2 cell membranes with a thin cell wall in-between made with less peptidoglycan

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8
Q

why is the structure of bacteria important in the mechanism of antibiotics?

A

Structure of cell wall and membrane is different to humans to can be used as a target for the antimicrobials without damaging host

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9
Q

List 5 mechanisms of action of antibiotics

A 
Inhibit cell wall synthesis
Alteration of cell membrane
Inhibit protein synthesis
Interfere with bacterial nucleic acid
Anti-microbial activity - disrupt processes needed for survival of the cell
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10
Q

What makes up the cell wall of the bacteria?

A

Peptidoglycan

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11
Q

Describe bacterial cell wall synthesis

A

2 amino sugars make up the peptidoglycan monomer unit (n-acetlyglucosamine and n-acetylmuramic acid)
This unit is transferred across the bacterial cell membrane in a lipid carrier to outside of the cell
Here the chains cross link and form peptidoglycan chain catalysed by penicillin binding protein

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12
Q

List the sites of action of antibiotics acting to inibit cell wall synthesis

A

Interfere with enzyme catalysing cross linkage - peptidoglycan chain cannot form
Interfere with peptidoglycan monomer
Interfere with lipid carrier do monomer unit cannot cross to the outside of the cell

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13
Q

What is the aim of interfering with formation of cell wall?

A

Cell lysis

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14
Q

How do beta-lactams work?

A

Inhibit peptidoglycan synthesis by binding to the penicillin binding protein - so cannot cross-link

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15
Q

How does vancomycin work?

A

Disrupt peptidoglycan cross-linkage by binding to peptidoglycan monomers

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16
Q

How does bacitracin work?

A

Disrupt lipid carrier required for glycol transport across the cell membrane

17
Q

What is the aim of antibiotics targeting the alteration of cell membrane?

A

Leakage of cell contents due to disruption of cross-membrane potential

18
Q

How do antibiotics such as polymyxins and daptomycins work (cell membrane)?

A

Depolarisation of cell and leakage of contents or lysis

19
Q

At what 2 sites can protein synthesis be inhibited?

A

30s ribosomes

50s ribosomes

20
Q

What ribosomal sub unit do aminoglycosides and tetracyclines act?

A

30s

21
Q

What ribosomal sub unit do macrolides act?

A

50s

22
Q

Describe bacterial protein synthesis?

A

mRNA attaches to 30s subunit of ribosome
tRNA brings amino acid to 50s subunit
Transpeptidation of amino acid to growing peptide from 50s unit
Ribosome translocates and peptide chain grows, ribosome moves along one codonalong mRNA and new molecules of tRNA attach to 50s

23
Q

How do tetracylines work?

A

Inhibit entry of incoming acetyl tRNA

24
Q

How do aminoglycosides work?

A

Inhibit the correct reading of mRNA

25
Q

how do macrolides work?

A

Inhibit translocation

26
Q

How does chloramphenicol work?

A

Inhibits transpeptidation

27
Q

How do quinolone work?

A

Inhibit DNA gyrases or topiosomerases that stop supercoiling of DNA

28
Q

How do metronidazoles work?

A

Metabolised into toxic metabolites which interfere with DNA - causing inhibitor of DNA replication

29
Q

How does rifampicin work?

A

binds to RNA polymerase inhibiting transcription

30
Q

How do sulphonamides work?

A

Inhibit folic acid production - inhibiting the production of DNa

31
Q

How can antibiotics be mis-used?

A

Incorrect dose
Incorrect duration
Inappropriate choice
Use in warranted situations

32
Q

What does antibiotic misuse cause?

A

Resistance

33
Q

What is MRSa treated with?

A

Vancomycin

34
Q

What are 2 classes of antimicrobial resistance?

A

Natural

Acquired

Human Diseases (37 decks)

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