Escape of Candida from Caspofungin Inhibition at Concentrations above the MIC (Paradoxical Effect) Accomplished by Increased Cell Wall Chitin; Evidence for β-1,6-Glucan Synthesis Inhibition by Caspofungin

Concentrations above the MIC of caspofungin allow growth of some Candida isolates. A strain demonstrating paradoxical growth was grown in the presence and absence of caspofungin, and the cell wall content was analyzed. Beta-1,3-glucan declined 81% in the presence of caspofungin, as expected. Beta-1,6-glucan declined 73%. Chitin increased 898%, demonstrating a mechanism for paradoxical growth-a rapid shift in the key polymer.