A 29-year-old man with non-gonococcal urethritis was treated with doxycycline followed by azithromycin, yet urethral symptoms and discharge persisted. NAAT of first-void urine detects Mycoplasma genitalium. Macrolide resistance in this organism is mediated by:
- A Mutations in the 23S rRNA gene ✓
- B Acquisition of the erm(B) methylase gene on a transposon
- C Hydrolysis by an inducible macrolide esterase enzyme
- D Overexpression of an efflux pump encoded by mef(A)
Correct answer: A. Mutations in the 23S rRNA gene
Explanation
Macrolide resistance in Mycoplasma genitalium arises from point mutations in domain V of the 23S rRNA gene, chiefly A2058G and A2059G, which alter the macrolide binding site on the ribosome. Resistance rates exceed 50 percent in many regions and predict azithromycin treatment failure, so guidelines recommend moxifloxacin after confirmed macrolide-resistant infection. erm(B), mef(A) and esterases are resistance mechanisms described in bacteria with cell walls such as streptococci, not in mycoplasmas.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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