Which of the following antifungals targets ergosterol?

Amphotericin B is a polyene antifungal that specifically targets ergosterol, which is a critical component of fungal cell membranes. By binding to ergosterol, Amphotericin B disrupts the integrity of the fungal cell membrane, leading to increased permeability and ultimately causing cell death. This mechanism of action is particularly effective against a wide variety of fungal pathogens, including Candida and Aspergillus species.

In contrast, metronidazole is an antibiotic that works primarily against anaerobic bacteria and certain protozoa, and it does not have any action related to ergosterol or fungal cell membranes. Cephalosporins are a class of beta-lactam antibiotics that act by inhibiting bacterial cell wall synthesis, which is unrelated to fungal treatment and the ergosterol target. Piperacillin, also a member of the penicillin family, works by interfering with bacterial cell wall synthesis and does not affect ergosterol.

Thus, Amphotericin B is the only drug listed that directly interacts with ergosterol, making it the correct choice.