Which organism is not targeted by echinocandins?

• A. Cryptococcus
• B. Candida species
• C. Aspergillus fumigatus
• D. Histoplasma

Answer: (A)

Echinocandins work by inhibiting the enzyme that makes β-1,3-glucan, a major component of many fungal cell walls. Fungi that rely on β-1,3-glucan for structural integrity are effectively weakened by this mechanism. Candida species have abundant β-1,3-glucan in their walls, so they are readily targeted by echinocandins. Cryptococcus, on the other hand, has a capsule and a cell wall with relatively low β-1,3-glucan content, so echinocandins show little to no activity against it. That makes Cryptococcus not a target for this class. Some fungi like Aspergillus have only limited or context-dependent susceptibility, and Histoplasma isn’t reliably affected by echinocandins, whereas Candida is the classic susceptible organism.