What is the mechanism of action of tetracyclines used to treat Donovanosis?
Answer
A 28-year-old male presents to the emergency room complaining of painless lesions on and near the perineum and genitals. The patient admitted to a recent episode of unprotected sexual acts. Physical exam revealed numerous lesions that appear as parasites embedded under the patient's skin. There was no regional lymphadenopathy. Culture of the organisms revealed dark-staining Donovan bodies on tissue biopsy. The causative species for this genital ulcerative disease are gram-negative bacteria Klebsiella granulomatis. Patient was diagnosed with Donovanosis. Patient was prescribed 100mg of Doxycycline twice a day for 3 weeks.
Doxycycline is a part of a drug class called tetracyclines. How do these antibiotics work? Tetracycline works by inhibiting protein synthesis by binding to the bacterial ribosome involved in the translation process of protein synthesis. The bacterial ribosome is 70S, which is made up of two svedberg subunits. A 50S and a 30S make up the 70S. There are three binding sites for the tRNA molecule, an A site, a P site, and an E site. Tetracycline binds to the 30S ribosomal subunit, cancelling the assembly of the two ribosomes, and blocking tRNA binding. If proteins from the bacteria are inhibited from being made, the infection is treated until cured.
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