A 65-year-old immunocompromised patient is started on ceftaroline for MRSA pneumonia. Which structural feature of ceftaroline distinguishes it from other cephalosporins and confers MRSA activity?
- A A 1,3-thiazole sidechain at C-3 that allows binding to PBP2a (the mecA-encoded penicillin-binding protein) ✓
- B A catechol sidechain that chelates iron to enhance outer membrane penetration
- C Resistance to all beta-lactamases including metallo-beta-lactamases
- D An intact beta-lactam ring with no R1 sidechain, conferring pan-activity
Correct answer: A. A 1,3-thiazole sidechain at C-3 that allows binding to PBP2a (the mecA-encoded penicillin-binding protein)
Explanation
Ceftaroline fosamil is the first cephalosporin with reliable activity against MRSA. Its anti-MRSA activity is conferred by its unique C-3 1,3-thiazole ring side chain that enables high-affinity binding to PBP2a, the altered penicillin-binding protein encoded by the mecA gene responsible for MRSA resistance. This allows ceftaroline to form a stable acyl-enzyme complex with PBP2a, inhibiting cell wall synthesis even in MRSA. It does not cover metallo-beta-lactamase producers (e.g., NDM organisms).
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.