What is the mechanism of action of echinocandins and their primary activity spectrum?

• A. Inhibit 1,3-beta-D-glucan synthase; active mainly against Candida species and many molds including Aspergillus; not active against Cryptococcus or Mucorales.
• B. Inhibit ergosterol synthesis; active against Cryptococcus and Mucorales
• C. Inhibit nucleic acid synthesis; broad-spectrum antifungal
• D. Bind fungal DNA; broad activity across fungi and bacteria

Answer: (A)

Echinocandins block the enzyme 1,3-beta-D-glucan synthase, which stops the production of beta-1,3-glucan, a vital polymer in the fungal cell wall. Without this cell wall component, many fungi cannot maintain their integrity and die or stop growing. This mechanism explains why these drugs are highly effective against Candida species and show activity against several molds, including Aspergillus. They, however, are not active against Cryptococcus neoformans or Mucorales because those fungi either rely less on beta-1,3-glucan or use wall structures that aren’t disrupted by this drug class. In short, echinocandins target the fungal cell wall and have strong activity against Candida and many molds, but not Cryptococcus or Mucorales.