Set 4: Mechanisms of Drug Action

What are the five primary sites of action for antimicrobial drugs?

1) inhibition of Cell wall synthesis,

2) inhibition of Nucleic acid (DNA/RNA) structure/function

3) Inhibition of Protein synthesis (ribosomes)

4) Interference of Cytoplasmic membrane structure/function

5) Inhibition of Folic acid synthesis

What is the use of Methicillin & Nafcillin?

Effective against Staphylococcus

Describe Ampicillin

Broad-spectrum and acid-stable

What is Ticarcillin effective against?

Effective against Pseudomonas and Proteus

How do penicillins work, and what is the difference between Penicillin G and V?

They resemble peptidoglycan, so enzymes for cell wall growth bind to penicillin instead of normal substrtate;

• Penicillin G is acid-labile (destroyed by stomach acid), gram positive microbes

• Penicillin V is acid-stable.

When is Vancomycin typically used?

• Narrow-spectrum

• Gram positive

• used for resistant S. aureus (MRSA) or penicillin allergies.

When is Carbapenems typically used?

• Broad-spectrum

• used for patients with penicillin allergies or severe multi-drug resistant infections

What is the mechanism of an aminoglycoside?

• They bind to the 30S ribosomal subunit, causing mRNA misreading, and also contain abnormal proteins

• broad spectrum, bactericidal

What was aminoglycoside used to treat?

TB, Bubonic plague (Yersinia pestis)

Give examples of an aminoglycosides

Streptomycin, Gentamicin, and Neomycin, Kanamycin

Which drug class interferes with folate metabolism, and what are the consequence?

Sulfonamides (Sulfa drugs):

• broad spectrum, bacteriostatic

• they block enzymes needed for tetrahydrofolate synthesis, preventing the production of DNA, RNA, and amino acids.