Echinocandins inhibit 1,3-beta-D-glucan synthesis. What is their primary spectrum of activity?

• A. Inhibit ergosterol synthesis; active against Cryptococcus.
• B. Inhibit DNA synthesis; active against bacteria.
• C. Inhibit 1,3-beta-D-glucan synthesis; active against Candida species; some Aspergillus; not active against Cryptococcus.
• D. Bind to bacterial cell wall peptidoglycan.

Answer: (C)

Echinocandins work by inhibiting 1,3-beta-D-glucan synthase, blocking production of 1,3-beta-D-glucan that strengthens the fungal cell wall. Because Candida species rely heavily on this glucan, blocking its synthesis weakens their walls and effectively controls Candida infections. They also have activity against some molds, notably certain Aspergillus species, but they are not active against Cryptococcus, which has a different cell wall composition and relies less on this glucan pathway. So the primary spectrum is activity against Candida, with some Aspergillus activity, and no activity against Cryptococcus. Other options describe different mechanisms (ergosterol synthesis, DNA synthesis inhibition, or bacterial cell wall targets) that don’t apply to echinocandins.