A patient with multibacillary leprosy is on dapsone, clofazimine, and rifampin. Which of the following is true regarding the mechanism of action of the medications listed?
- Dapsone is bacteriostatic because of its inhibitory effects on dihydrofolate reductase
- Dapsone is bacteriostatic because of its inhibitory effects on myeloperoxidase
- Clofazimine is bactericidal by directly inhibiting bacterial DNA polymerase
- Rifampin is bacteriostatic by inhibiting RNA synthesis by blocking DNA-dependent RNA polymerase
- Rifampin is bactericidal by inhibiting RNA synthesis by blocking DNA-dependent RNA polymerase
Answer(s): E
Explanation:
A, B – false – dapsone inhibits bacterial synthesis of dihydrofolic acid, via competition with para- aminobenzoate for the active site of dihydropteroate synthetase. Dapsone is both bacteriostatic and weakly bactericidal against M. leprae. Neither of the listed mechanisms are the cause of these effects. C – False – A substance with both anti-leprosy and anti-inflammatory activity, clofazimine is weakly bactericidal against M. leprae by binding to the guanine bases of bacterial DNA, not DNA polymerase directly. D – False – See below. E – True – Rifampin is bactericidal by inhibiting RNA synthesis by blocking DNA-dependent RNA polymerase.
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