Question

Antimicrobial Drugs

1. Why do antibiotics that target bacterial protein synthesis usually have a broader spectrum of activity compared to antibiotics that target the peptidoglycan integrity?

2. If your only treatment option is a highly toxic antibiotic (such as chloramphenicol), how could you adjust the treatment protocol to lessen its negative effects?

3. Suppose that a patient that suffers from a Gram-positive bacterial infection develops an allergic reaction to amoxicillin. What alternative antimicrobial treatment from the same general group of antibiotics would you recommend?

4. Summarize the antimicrobial action of each of the three components in Neosporin. Why do you think these three were combined?

5. Why does tuberculosis treatment require multiple antimicrobial drugs? Provide examples.

Answer 1

Ans .(1) Antibiotic that target bacterial protein synthesis usually have a broader spectrum of activity compared to antibiotics that target peptidoglycan integrity, because the 70S ribosome is very similar among different types of bacteria and because many of these antibiotics can penetrate well into different types of cells. The ribosome is a major bacterial target for antibiotics. Drugs inhibit ribosome function either by interfering messenger RNA translation or by blocking the formation of peptide bonds at the peptidyl transferase centre.

Ans .(2) To reduce the risk of side effects , treatment duration should be as short as possible . People with liver or kidney problems may need lower doses. Chloramphenicol cannot be recommended as a first - line treatment for respiratory tract infections, meningitis, enteric fever as alternatives are probably more effective.

Ans .(3) Acceptable alternatives include cefdinir (omnicef) or cefuroxime (ceftin).

Ans .(4) Neosporin is an over the counter (OTC) triple - antibiotic ointment containing 3 separate antibacterial agents:-

i) Neomycin :- It inhibits bacterial DNA polymerase.

ii) Bacitracin :- It blocks the cell wall formation by interfering with the dephosporylation of the lipid compound that carries peptidoglycans to the growing microbial cell wall.

iii) Polymyxin :- After binding to lipopolysaccharide in the outer menbrane of gram negative bacteria, polymyxins disrupt both the outer and inner membranes. The hydrophobic tail is important in causing membrane damage, suggesting a detergent - like mode of action.

Ans .(5) Multiple drug regimens are necessary to prevent the development of drug resistant strains, an event that occurs at different frequencies depending upon which drug is considered.