Antibiotics

Question 1

What are the subgroups of Beta-lactams?

Answer 1

Penicillins, Carbapenems, Cephlosporins, monobactams.

Question 2

The 3 modes of action of Beta-lactams.

Answer 2

1) Bind to PBP- transpeptidases. Prevents cross linking and causes cell lysis.
2) Incorporated in peptide side chain, prevents cross linking and causes cell lysis.
3) Stimulate autolysins, which break down cell wall and cause cell lysis.

Question 3

What other group of antibiotics target the cell wall synthesis? Example of this group?

Answer 3

Glycopeptides. Vancomycin.

Question 4

The 2 modes of action of Glycopeptides.

Answer 4

1) Prevents glycosylase enzyme from adding PG monomer onto PG chain.
2) Prevents cross linking.

Question 5

What 2 groups of antibiotics target the cell membrane? Example of each group.

Answer 5

Polymyxins (Colistin) and Lipopeptides (Cubicin).

Question 6

Do Polymyxins work on G+ve or G-ve bacteria?

Answer 6

Gram negative.

Question 7

How do Polymyxins work?

Answer 7

Disrupt membrane leading to leakage of cytoplasmic contents.

Question 8

4 ways Antimicrobials act on Nucleic Acid?

Answer 8

Metabolic inhibitors of NA synthesis. Affect DNA replication. Affect RNA polymerase. Affect DNA.

Question 9

Example of Fluoroquinolones and what is the MOA?

Answer 9

Ciprofloxacin. Bind to type 2 DNA gyrase (removes dna supercoils ahead of replication fork) and/or type 4 DNA topoisomerase (seperates dna after replications).

Question 10

Tetracyclines and aminoglycosides target what?

Answer 10

30S of ribosome.

Question 11

Macrolides, streptogramins, lincosamides, oxazolidinones and chloramphenicol all target what?

Answer 11

50S of ribosome.

Question 12

Do tetracylines or aminoglycosides bind irreversibly to A-site on 16S rRNA in 30S subunit?

Answer 12

Aminoglycosides.

Question 13

Which leads to bactericidal? Reversible or irreversible binding to A-site on 16S rRNA in 30S subunit?

Answer 13

Irreversible.