Answer to Question #39096 in Microbiology for casey

Question

Why does penicilin cause so few side effects while amphotericin B causes so many? Consider the structure of prokaryotic and eukaryotic cells when giving your answer?

Answer 1

Penicillin disrupts the formation of peptidoglycan cross-links in the bacterial cell wall. It inhibits bacterial cell growth but has little effect on host cells because they lack cell wall.
Amphotericin B from Streptomyces spp. binds to the sterols in fungal membranes, disrupting membrane permeability and causing leakage of cell constituents. Mammalian and fungal membranes both contain sterols. Therefore amphotericin B molecules can form pores in the host membrane as well as the fungal membrane. Thus, amphotericin B is quite toxic and used only for serious, life-threatening infections.