Aminoglycoside-modifying enzymes (AMEs) represent the most common resistance mechanism to aminoglycosides. The enzyme class that confers the broadest aminoglycoside resistance by modifying the 2'-position of the 2-deoxystreptamine ring is:
- A Aminoglycoside nucleotidyltransferases (ANTs), specifically ANT(2'')
- B Aminoglycoside acetyltransferases (AACs), specifically AAC(6') ✓
- C Aminoglycoside phosphotransferases (APHs), specifically APH(3')
- D 16S rRNA methyltransferases (RMTs) methylating G1405
Explanation
AAC(6')-Ib is the most clinically prevalent aminoglycoside acetyltransferase. It acetylates the 6'-amino group of aminoglycosides (tobramycin, amikacin, gentamicin), reducing binding to the 16S rRNA decoding site on the 30S ribosomal subunit. A variant AAC(6')-Ib-cr also inactivates fluoroquinolones by acetylating their piperazinyl nitrogen, making it a bifunctional resistance enzyme. APH(3') phosphorylates the 3'-hydroxyl (affects kanamycin, neomycin). ANT(2'') adenylates gentamicin and tobramycin. RMTs (like ArmA, RmtB) are plasmid-borne methylases causing pan-aminoglycoside high-level resistance by methylating G1405 in 16S rRNA, preventing ribosomal binding entirely.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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