Aim: Amphotericin B (AmB) is a wide spectrum antifungal drug which is used for the treatment of invasive fungal infections. Among the fungal pathogens, Candida lusitaniae has been reported to be resistant to AmB in-vitro. Therefore, AmB is not recommended for the treatment of C. lusitaniae infections. There are conflicting data on this subject in the literature. Some of the studies showed that minimal inhibitory concentration (MIC) values increased following exposure to AmB, while the others indicated that all C. lusitaniae were fully susceptible to AmB. The aim of the present study was to evaluate the AmB susceptibility of the C. lusitaniae strains.

Materials and Methods: The study included 60 C. lusitaniae strains obtained from four different teaching hospitals in Turkey. The strains were identified at species level by using conventional methods in three of the centers and by MALDI-TOF method in one center. In vitro susceptibility testing was performed by E-test and Clinical and Laboratory Standards Institute (CLSI) reference microdilution method.

Results: AmB MIC range was found as 0.125-2 μg/ml, MIC50 value was 0.5 μg/ml, and MIC90 value was 1 μg/ml by microdilution method. MIC range, MIC50, and MIC90 values were 0.012-2 μg/ml, 0.25 μg/ml, and 0.75 μg/ml by E-test method, respectively. The number of isolates with MIC ≥1 μg/ml were 8 (13%), and 6 (10%), for microdilution and E-test methods, respectively. MIC value was 2 μg/ml for two strains by microdilution method, and one strain by E-test method.

Conclusion: Our results showed that C. lusitaniae strains which were considered as intrinsically resistant, were susceptible to AmB. Although, more definite conclusions achieved by in vivo studies are required, this study indicated that AmB could be a good choice for the treatment of infections caused by C. lusitaniae.