Which of the following are examples of bactericidal antibiotics?

• A. Penicillin, Vancomycin
• B. Tetracycline, Sulfa Drugs
• C. Erythromycin, Azithromycin
• D. Chloramphenicol, Clindamycin

Answer: (A)

Bactericidal antibiotics actively kill bacteria, rather than just stopping their growth. Penicillin and vancomycin fit this pattern because they disrupt bacterial cell wall synthesis. Penicillin inhibits penicillin-binding proteins, weakening the cell wall and causing bacterial lysis during growth. Vancomycin blocks the construction of the cell wall precursors, preventing cross-linking and leading to death of the bacteria.

Many other antibiotics are typically bacteriostatic, meaning they inhibit growth and rely on the immune system to clear the infection. Tetracycline and sulfa drugs inhibit essential processes like protein synthesis and folate synthesis, respectively, without directly causing cell death in most cases. Macrolides such as erythromycin and azithromycin also usually stop protein synthesis and are considered bacteriostatic, though very high concentrations can be bactericidal against some organisms. Chloramphenicol and clindamycin are generally bacteriostatic as well, with limited circumstances where they can be bactericidal.

So, the examples that are best recognized as bactericidal are penicillin and vancomycin.