Abstract:

Objective To dynamically observe the paradoxical effect （inhibitory at low concentratin but promotive at high concentration） of caspofungin and micafungin across Candida species in vitro. Methods A broth microdilution testing was performed following the Clinical and Laboratory Standards Institute （CLSI） M27-A2 document to observe the paradoxical effect of caspofungin and micafungin across 85 Candida strains. The growth of Candida was observed on a daily basis for 7 days. Results At 48 hours, the prevalence of paradoxical growth in C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. dubliniensis and other species of Candida was 90%, 20%, 41.7%, 37.5%, 33.3% and 28.6% respectively after caspofungin treatment, and 5%, 0, 0, 25%, 33.3% and 0 respectively after micafungin treatment. The concentration range of caspofungin required for the paradoxical growth of C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. dubliniensis and other species of Candida was 4－16, 8－32, 8－32, 2－8, 2－8, 8－32 μg/ml respectively, and that of micafungin for the paradoxical growth of C. albicans, C. tropicalis and C. dubliniensis was 4－16, 4－32 and 1－8 μg/ml, respectively. After 48 hours, the prevalence of paradoxical growth still increased in C. parapsilosis, C. glabrata, and other species of Candida following caspofungin treatment, and in C. albicans and C. glabrata following micafungin treatment. Conclusions The occurrence, and time of occurrence, of paradoxical effect of echinocandins is Candida species- and drug-specific. The prevalence of paradoxical effect is higher for caspofungin than for micafungin, which seems unrelated to their MICs against Candida species.

Key words: Dynamic