Which antibiotic is commonly used as an example of a bacteriostatic agent?

• A. Tetracycline
• B. Penicillin
• C. Vancomycin
• D. Ciprofloxacin

Answer: (A)

The idea being tested is distinguishing bacteriostatic versus bactericidal antibiotics. Tetracycline is commonly used as an example of a bacteriostatic agent because it inhibits bacterial growth by blocking protein synthesis. It binds to the 30S ribosomal subunit, preventing the correct pairing of aminoacyl-tRNA with the ribosome, which stops elongation of the protein chain. With growth halted, the infection is cleared mainly by the host immune response rather than by immediate bacterial killing.

In contrast, the other commonly used drugs listed are typically bactericidal. Penicillin and vancomycin disrupt cell wall synthesis, leading to bacterial lysis. Ciprofloxacin interferes with DNA replication by inhibiting DNA gyrase, which rapidly kills bacteria. While some antibiotics can be bactericidal under certain conditions or against specific organisms, tetracycline is the classic example taught as a bacteriostatic agent.