耳念珠菌不同条件下生长特性及体内毒性

目的 探讨耳念珠菌在不同条件下的生长特性、代谢特点及体内毒性特征。方法 以白色念珠菌为参照，测定并比较耳念珠菌与白色念珠菌在常规培养条件、不同pH值和不同盐含量下的生长情况；利用微量生化反应管测定两种念珠菌糖醇发酵情况；以四周龄裸鼠为实验动物，用随机数字表法分为3组，耳念珠菌感染组、白色念珠菌感染组和生理盐水对照组，5只/组。耳念珠菌感染组和白色念珠菌感染组取0.3 mL已调至5×109 cfu/mL菌液，对裸鼠进行灌胃处理，建立胃肠道感染模型，对照组用等量生理盐水灌胃，取肝脏、肾脏、肠、粪便和血液等标本，通过真菌培养和组织病理学变化分析耳念珠菌的体内分布和毒性特征。结果 耳念珠菌的对数生长期约为8~24 h，约在24 h后进入生长稳定期，最适生长的pH值范围为5~7，生长模式与白色念珠菌相同；耳念珠菌在浓度为5%和10%的NaCl培养基中生长情况优于白色念珠菌，能发酵葡萄糖、蔗糖、海藻糖和山梨醇；从裸鼠的粪便、血液、肝脏和肾脏组织中分离出耳念珠菌，肝脏载菌量最多为5.7 log10 cfu/g，其可造成肝组织和肠组织病理学改变，但病变程度比白色念珠菌弱。结论 耳念珠菌在弱酸或中性条件下最适宜生长，具有高耐盐性，在免疫抑制状态下感染机体后，存在突破肠屏障入血及随血流播散并导致组织病变的可能。

Study on growth characteristics of Candida auris under different conditions in vitro andits in vivo toxicity

Objective To investigate the characteristics of growth and metabolism and the in vivo toxicity of Candida auris underdifferent conditions. Methods We observed the growth of Candida auris and Candida albicans under routine culture conditionsand in different pH and salt concentrations, and compared their activities of sugar fermentation using microbiochemicalreaction tubes. Four-week-old nude mice were randomized into Candida auris infection group (n=5), Candida albicans infectiongroup (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 vivodistribution and toxicity of Candida albicans by fungal culture and histopathological examination. Results Candida aurisexhibited logarithmic growth at 8-24 h after inoculation and showed stable growth after 24 h. Candida auris showed optimalgrowth within the pH value range of 5-7 with a growth pattern identical to that of Candida albicans. Candida auris grew betterthan 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 highestfungal load (5.7 log10 cfu/g). Candida auris could cause pathological changes in the liver and intestine of the mice, but with alesser severity as compared with Candida albicans. Conclusions Candida auris exhibits optimal growth in mildly acidic orneutral conditions with a high salt tolerance, and can potentially penetrate the intestinal barrier into blood and lead to tissueinjuries in hosts with immunosuppression.