Pharmacology Which of the following antimicrobial is effective against an organism producing extended spectrum beta lactamase: A Amoxicillin–Clavulanic acid. B Cefepime C Piperacillin-Tazobactam. D Ceftriaxone. 💡 Explanation Which of the following antimicrobial is effective against an organism producing extended spectrum beta lactamase: ✓ Correct Answer: C. Piperacillin-Tazobactam.