Breakthrough Candidemia Due to Multidrug-Resistant Candida glabrata during Prophylaxis with a Low Dose of Micafungin

We identified a case of breakthrough candidemia in a 25-year-old patient receiving micafungin prophylaxis (50 mg/day). Five Candida glabrata isolates were obtained from blood cultures and were classified as multidrug-resistant isolates, since all of them exhibited high MICs for echinocandin and azole drugs. A mutation (S663F) in hot spot 1 of the FKS2 gene was found in all five isolates. This mutation yielded a 1,3-beta-D-glucan synthase enzyme with highly reduced sensitivities to echinocandin drugs.