Which pair of antibiotics is given as an example of bactericidal agents?

• A. Penicillin, Vancomycin
• B. Tetracycline, Sulfa Drugs
• C. Erythromycin, Azithromycin
• D. Ciprofloxacin, Doxycycline

Answer: (A)

Bactericidal drugs kill bacteria outright, while bacteriostatic drugs merely stop them from growing and rely on the immune system to finish the job. Penicillin and vancomycin both disrupt cell wall synthesis, which is essential for bacterial survival during growth. When the cell wall is compromised in actively dividing bacteria, the cell can’t maintain its structure and eventually dies, so these drugs are typically bactericidal.

In contrast, many other common antibiotics inhibit processes like protein synthesis or folate synthesis, which more often result in stopping bacterial replication rather than causing immediate death. Tetracycline and sulfa drugs are generally bacteriostatic; macrolides such as erythromycin and azithromycin are usually bacteriostatic as well. Ciprofloxacin is bactericidal, but pairing it with doxycycline, which is bacteriostatic, makes the combination not a consistent example of two bactericidal agents.

So, the pair that best represents bactericidal activity is penicillin together with vancomycin, since both tend to kill susceptible bacteria rather than merely inhibiting their growth.