A 28-year-old woman with cystic fibrosis presents with fever and purulent sputum. Sputum culture grows Pseudomonas aeruginosa. She gives a history of a severe anaphylactic reaction to amoxicillin in childhood. Which antibiotic can be safely used to cover Pseudomonas in this patient?
- A Ceftriaxone
- B Piperacillin-tazobactam
- C Imipenem-cilastatin
- D Aztreonam ✓
Correct answer: D. Aztreonam
Explanation
Aztreonam is a monobactam that binds only PBP3 of Gram-negative bacteria and has negligible cross-reactivity with beta-lactams acting on Gram-positive PBPs, so it is considered safe in patients with IgE-mediated penicillin allergy. Piperacillin-tazobactam and imipenem carry real risk of cross-reaction, and ceftriaxone lacks reliable Pseudomonas activity at standard doses.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.