Antibitotics - DNA Synthesis Inhibators

Question 1

How do Sulphonamides work ?

Answer 1

Bacteria cannot use external sources of folate, so they need to make their own for essential functions of DNA synthesis. Sulphonamides inhibit bacterial folate synthesis and slow bacterial growth.

Question 1

What are the two DNA synthesis inhibitor antibitotics?

Answer 1

• Sulphonamides
• Trimethoprim
• nitrofurantoin
• Fluoroquinolones

Question 2

How does trimepthorpin work ?

Answer 2

Inhibit bacterial folate synthesis and slow bacterial growth.

Question 3

What two medications can be given together to completely inhibit folate synthesis ?

Answer 3

Sulphonamides and trimethoprim

eg - co-trimazole - (Sulfamethoxazole + trimethoprim) - Combination now reserved for pneumocystis pneumonia in immunosuppressed patients

Question 4

What is co-trimazole a combination of ?

Answer 4

Co-trimoxazole is a combination of two antibacterial medicines - a sulfonamide medicine called sulfamethoxazole, and trimethoprim.

Question 5

What is the mechanism of action for nitrofurantoin?

Answer 5

Nitrafurantoin is an active metabolite.

Nitrofurantoin is metabolised (Reduced) in bacterial cells by nitrofurantoin reductase. Its active metabolite damages bacterial DNA and causes cell death (Bacterialcidal )

Question 6

How do fluoroquinolone work ?

Answer 6

Inhibition of unwinding DNA supercoils, which kills the bacteria.

• Resistance is an issue – reserved for 2nd/3rd line use

Question 7

Name two fluroquinolones

Answer 7

• Ciprofloxacin
• Levoflaxacin

Question 8

What are two issues with fluroquinolones ?

Answer 8

Increased risk of arrhytmias - prolonged QT interval

Low seizure threshold - especially when in use with NSAIDS.