What is the primary action of Benzylpenicillin?

Benzylpenicillin, also known as penicillin G, primarily acts as a bactericidal agent by inhibiting bacterial cell wall synthesis. This action is crucial in combating bacterial infections, as it disrupts the integrity of the cell wall, leading to cell lysis and death. The mechanism involves binding to penicillin-binding proteins (PBPs), which are essential for the synthesis of peptidoglycan, a key component of bacterial cell walls.

When PBPs are inhibited, the bacteria are unable to properly maintain their cell structure, ultimately resulting in their breakdown. This is particularly effective against Gram-positive bacteria, which have a thick peptidoglycan layer in their cell wall.

Other choices reflect actions that are not characteristic of Benzylpenicillin. For example, inhibiting bacterial protein synthesis relates to antibiotic classes like macrolides or tetracyclines, while inactivating viral DNA pertains to antiviral medications, and preventing fungal cell membrane formation is associated with antifungal agents like azoles or polyenes. Therefore, the correct choice highlights Benzylpenicillin's specific mechanism of action in pharmacology.