Antimicrobial therapies

Question 1

How can antibiotics target the cell wall?

Answer 1

1. Penicillin, Methicillin
2. Inhibits bacterial cell wall peptidoglycan formation
   - Binds transpeptidases (Penicillin-binding proteins)
3. Problems with penicillin resistance – β-lactamase

Question 2

What are Fluoroquinolones? What is it for gram positive and gram negative?

Answer 2

• Target DNA synthesis
  1. Inhibit DNA replication
  2. DNA gyrase in Gram -ve
  3. Topoisomerase IV in Gram +ve

Question 3

What is Chloramphenicol?

Answer 3

• Chloramphenicol (50s) - prevents protein elongation by inhibiting peptidyl transferase activity
• Ribosome antibiotic

Question 4

What is Aminoglycosides?

Answer 4

• Aminoglycosides (30s) – affects RNA proofreading and causes damage to cell membrane
• Ribosome antibiotic

Question 5

What is macrolides?

Answer 5

• Macrolides (50s) - prevents amino-acyl transfer and truncation of polypeptides
• Ribosome antibiotic

Question 6

What are tetracyclines?

Answer 6

• Tetracyclines (30s) - inhibit translation: stops the binding of aminoacyl-tRNA to the mRNA translation complex
• Ribosome antibiotic

Question 7

What does Acyclovir do?

Answer 7

-Antiviral
E.g. HSV, varicella zoster (chickenpox)
-Converted to acyclovir triphosphate -> inhibits DNA polymerases-> prevents viral DNA synthesis

Question 8

What is the process of antibiotic resistance?

Answer 8

1. high number of bacteria and a few are resistant to antibiotics
2. Antibiotic kills pathogenetic bacteria as well as the goof bacteria within he body (probiotics)
3. The antibiotic resistant bacteria now proliferates without competition
4. The bacteria can transfer the antibiotic resistant gene to other bacteria via plasmids (conjugation)

Question 9

What are different method of antibiotic resistance?

Answer 9

1. Altered target site.
   - Methicillin-resistance involves an alternative PBP (PBP2a) with low affinity for beta-lactams
2. Inactivation of antibiotic.
   - B-lactamase destroys b-lactams
3. Altered metabolism
   - ↑ production of PABA confers resistance to sulfonamides
4. Decreased drug accumulation
   - Antibiotic efflux pump