Which of the following is NOT a macrolide antibiotic?

Amoxicillin is correctly identified as not being a macrolide antibiotic because it belongs to the penicillin group of antibiotics, which is distinctly different from macrolides. Macrolides, such as Azithromycin, Clarithromycin, and Erythromycin, are characterized by their large macrocyclic lactone ring structure and are primarily used to treat respiratory tract infections, skin infections, and certain sexually transmitted infections.

In contrast, Amoxicillin works by inhibiting bacterial cell wall synthesis and is typically used for conditions like otitis media, pneumonia, and urinary tract infections. This difference in mechanism and chemical structure clearly distinguishes Amoxicillin from the macrolide class, making it the correct answer for this question.