Which of the following is NOT a macrolide antibiotic?

Fidaxomicin, azithromycin, and clarithromycin are all part of the macrolide antibiotic class, which is characterized by their large macrocyclic lactone ring structure and their mechanism of action that involves inhibition of bacterial protein synthesis. This class of antibiotics is commonly used to treat various infections, particularly those caused by Gram-positive bacteria and some anaerobes.

Amoxicillin, on the other hand, is a penicillin-type antibiotic that functions by interfering with bacterial cell wall synthesis. It is different in both its chemical structure and mechanism of action. Therefore, when identifying which option does not belong to the macrolide category, amoxicillin is clearly the correct choice, as it is not classified as a macrolide and operates through an entirely different biological pathway. This distinction is essential for understanding antibiotic classes and their respective uses in clinical practice.