Abstract: Objective To determine the susceptibility of yeasts and to explore the antifungal mechanismof Lisea cubeba oil,so as to provide evidence for the development of antifungal medicinal herbs.Methods The minimuminhibitory concentrations(MIC)of Lisea cubeba oil and fluconazole were determined by broth microdilution method according to the National Committee on Clinical Laboratory Standards(NCCLS)reference method for broth dilution antifungal susceptibility testing of yeasts.Ultra-structural changes of C.krusei were observed by electron microscopy before and after Lisea cubeba oil treatment.Results Five previously identified quality control(QC)strains(Candida albicans,Candida tropicalis,Candida glabrata,Candida parapsilosis,Candida krusei)were susceptible to Lisea cubeba oil,their MICs were 14.14±3.64μg/mL,23.22±2.85μg/mL,31.24±2.88μg/mL,76.19±4.40μg/mL,28.30±2.54μg/mL,respectively.After treatment with Lisea cubeba oil the mor-phology and ultrastructure of Candida krusei showed obvious changes:their cell wall and cytoplasmic membrane ruptured;intracellar components dissolved;organellae swollen and dissolved.There were no changes observed in the morphology and ultrastructure of C.krusei treated with fluconazole.Conclusions The data indicate that Lisea cubeba oil has antifungal effect not only on C.albican and other medically important Candida spp.,but also on fluconazole resistant isolates such as C.krusei and thus has great clinical importance.The antifungal mechanismof Lisea cubeba oil may be that the structure of cell wall and cell membrane of C.krusei being inhibited.

Key words: Microbial sensitivity tests, Lisea cubeba, Candida, Fluconazole