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MICROBIO > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What are antibiotics?

A

A drug used to treat or prevent infections caused by micro-organisms

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2
Q

Bacteriostatic

A

Inhibits the growth of bacteria

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3
Q

Bacteriocidal

A

Kills bacteria

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4
Q

Properties of an ideal antibiotic (x7)

A
  1. Selective toxicity, with minimal toxicity to host
  2. Bacteriocidal (kills bacteria)
  3. Long half-life (e.g. low binding to plasma proteins)
  4. DNA gyrases (DNA topoisomerase II) - helps in DNA unwinding
  5. Appropriate tissue distribution
  6. No adverse drug interactions (Reduces the risk of hypersensitivity)
  7. Oral and parenteral preparations (i.e. not intravenous)
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5
Q

Bacteria targets of inhibition (x5)

A
  1. Bacterial cell wall
  2. Inhibitors of RNA synthesis / translation
  3. Targeting DNA replication
  4. Targeting gyrases
  5. Targeting metabolic pathways
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6
Q

What is the process involved in cell wall synthesis?

A

Transpeptidation - formation of peptide bonds between the 3rd a.a. in one pentapeptide (usually mDAP) and the 4th a.a. in an adjacent pentapeptide, D-Ala, accompanied by the release of a 2nd D-Ala.

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7
Q

What possess transpeptidase activity?

A

Pencillin-binding proteins

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8
Q

What is the target of the Beta-lactams class of antibiotics?

A

Penicillin-binding proteins

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9
Q

Mode of action of B-lactam class of antibiotics

A

Bind to penicillin binding proteins, inhibiting their transpeptidase activity. This prevents the cross-linking of peptide side chains and cleavage of terminal D-Ala-D-Ala dipeptide, hence no energy is released and no peptide bridge (cross-links) can form.

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10
Q

What are autolysins?

A

Endogenous enzymes that degrade already mature peptidoglycan / the components of a biological cell or a tissue in which it is produced.

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11
Q

List the members of the beta-lactam class of antibiotics (x6)

A
  • penicillin
  • amoxicillin
  • flucloxacillin
  • co-amoxicillin
  • cephalosporins
  • carbapenems
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12
Q

Which antibiotic is used in the treatment of MRSA?

A

Vancomycin

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13
Q

Which component of the bacterial cell does vancomycin target?

A

Cell wall

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14
Q

How does vancomycin work?

A

Vancomycin binds to the terminal D-Ala-D-Ala end of peptide side chains, preventing their binding to PBPs, hence preventing its incorporation into the cell wall

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15
Q

Name the antibiotics that work by inhibiting RNA synthesis/translation (x6)

A
  1. Streptomycin (Aminoglycosides)
  2. Tetracycline
  3. Clindamycin (Lincosamides)
  4. Erythromycin (Macrolides)
  5. Fusidic acid
  6. Chloramphenicol
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16
Q

Name the antibiotics that work by targeting DNA Replication / DNA gyrase

A
  1. Ciprofloxacin

2. Metronidazole (Nitroimidazole)

17
Q

What cells do streptomycin work on?

A

Gram-negative and some Gram-positive bacteria

Blocks the initiation complex on the 70S subunit

18
Q

How do tetracyclines work?

A

Binds to the 30S ribosomal subunit and interferes with the binding of aminoacylated tRNA molecules to the ribosomal A site –> Preventing attachment and stops chain elongation

19
Q

What treatment is clindamycin used in?

A

Osteomyelitis

bc of its tendency to concentrate in bone

20
Q

What does erythromycin act on?

A

Gram-positive bacteria; Neisseria and Haemophilus

21
Q

What does synergism mean in respect to antibiotic treatment?

A

Combined activity of antibiotics is greater than the activity expressed from the effect of each antibiotic

22
Q

Mode of action of Metronidazole

A

The drug is activated under anaerobic conditions to form a toxic intermediate that induces DNA strand breakage

23
Q

What are inhibitors of folic acid synthesis? (x2)

A

Sulphonamides

Trimethroprim

24
Q

What do Quinolones target?

A

DNA replication, by preventing the supercoiling of DNA

25
Q

Mode of action of Sulphonamides

A

Sulphonamides target metabolic pathways by inhibiting folic acid synthesis. They are analogues of para-aminobenzoic acid and inhibits pteridine synthetase

26
Q

Mode of action of Trimethroprim

A

Sulphonamides target metabolic pathways by inhibiting folic acid synthesis. They are analogues of pyrimidine and inhibits dihydrofolate reductase.

27
Q

What does metronidazole protect against?

A

Anaerobes and some parasites (protozoa)

MICROBIO (16 decks)

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