Abstract: Objective To investigate the characteristics of growth and metabolism and the in vivo toxicity of Candida auris under different conditions. Methods We observed the growth of Candida auris and Candida albicans under routine culture conditions and in different pH and salt concentrations, and compared their activities of sugar fermentation using microbiochemical reaction tubes. Four-week-old nude mice were randomized into Candida auris infection group (n=5), Candida albicans infection group (n=5) and control group (n=5) for intragastric administration of 0.3 mL suspension the two Candida species (5×109 cfu/mL) or 0.3 mL normal saline. Samples of the liver, kidney, intestine, feces and blood were taken for analysis of the in vivo distribution and toxicity of Candida albicans by fungal culture and histopathological examination. Results Candida auris exhibited logarithmic growth at 8-24 h after inoculation and showed stable growth after 24 h. Candida auris showed optimal growth within the pH value range of 5-7 with a growth pattern identical to that of Candida albicans. Candida auris grew better than Candida albicans in media containing 5% and 10% NaCl, and could ferment glucose, sucrose, trehalose and sorbitol. Candida auris could be isolated from the feces, blood, liver and kidney of infected nude mice, and the liver had the highest fungal load (5.7 log10 cfu/g). Candida auris could cause pathological changes in the liver and intestine of the mice, but with a lesser severity as compared with Candida albicans. Conclusions Candida auris exhibits optimal growth in mildly acidic or neutral conditions with a high salt tolerance, and can potentially penetrate the intestinal barrier into blood and lead to tissue injuries in hosts with immunosuppression.

Key words: Candida auris, growth characteristics, in vivo toxicity, Candida albicans