Which antibiotic is commonly considered bacteriostatic at standard doses?

• A. Penicillin
• B. Amoxicillin
• C. Tetracycline
• D. Cephalexin

Answer: (C)

Tetracycline is commonly considered bacteriostatic at standard doses because it halts bacterial growth by blocking protein synthesis. It binds to the 30S ribosomal subunit, preventing aminoacyl-tRNA from attaching to the ribosome and stopping elongation. Without new proteins, bacteria can’t replicate, and the immune system must clear them.

In contrast, the other listed antibiotics are typically bactericidal. They disrupt cell wall synthesis—penicillins and cephalosporins like cephalexin do this by inhibiting enzymes essential for building the cell wall—leading to bacterial lysis and death. Amoxicillin behaves similarly.