Which of the following antibiotics is known for its bactericidal effect?

Fluoroquinolones are a class of antibiotics that are recognized for their bactericidal properties, meaning they can kill bacteria directly rather than merely inhibiting their growth. This is due to their mechanism of action, which involves the inhibition of bacterial DNA gyrase and topoisomerase IV—enzymes critical for DNA replication and repair in bacteria. As a result, fluoroquinolones are effective against a broad spectrum of both Gram-positive and Gram-negative bacteria, making them a widely used option in treating various bacterial infections.

In contrast, ganciclovir and acyclovir are antiviral medications that specifically target viral infections, particularly those caused by herpes viruses; thus, they do not have a bactericidal effect as they are not designed to act on bacterial cells. Ketoconazole is an antifungal agent, used primarily to treat fungal infections, and also does not possess antibacterial properties. Understanding the classification and mode of action of these drugs clarifies why fluoroquinolones are the only ones in this list that demonstrate a bactericidal effect.