Objectives
The prevalence of fungal infections increases significantly in the past two decades. Major infections (~70%) are caused by Candida species. Candida albicans is polymorphic yeast that grows as yeast form which can extend to hyphae or pseudohyphae form. Disseminated candidiasis is associated with 30–40% mortality in severely immunocompromised patients. We have established a simple, noninvasive zebrafish egg bath infection model, defined its optimal conditions, and evaluated the model with various C. albicans mutant strains. We also applied this model to study pathogenesis of other Candida spp.
Methods
Wild-type zebrafish (Danio rerio), aged approximately 8 -15 months were maintained in the zebrafish core facility at National Health Research Institutes (NHRI). One day post-fertilization, the embryos were sterilized using 0.028% chlorine bleach containing 0.0017% sodium hypochlorite to reduce the possibility of contamination. In general, after co-incubation, non-adhered Candida cells were removed from embryos by washing with egg water 3 times. Embryos incubated in 1 mL of egg water in 24-well plates at 30 ºC were imaged daily under an inverted microscope, with a beating heart used to indicate viability. 
Results
The deletion of SAP6 did not have significant effect on the virulence. By contrast, the deletion of BCR1, CPH1, EFG1, or TEC1 significantly reduced the virulence under current conditions. Furthermore, all embryos survived when co-incubated with bcr1/bcr1, cph1/cph1 efg1/efg1, efg1/efg1, or tec1/tec1 mutant cells.
Conclusion 
The results indicated that our novel zebrafish model is time-saving and cost effective. Recently, we extended our novel zebrafish egg infection model to study the pathogenesis of other common Candida species, including C. glabrata and C. parapsilosis.

8 / A Simple and Noninvasive Zebrafish Egg Infection Model for Studying Pathogenic Yeasts