敏感和耐药白念珠菌磷脂酶活力与其毒力关系的研究

目的：探讨白念珠菌氟康唑耐药和敏感菌株磷脂酶活力与菌株毒力之间的关系。方法：根据美国国家临床实验室标准化委员会（NCCLS）制订的M27-A方案筛选临床分离的白念珠菌氟康唑耐药（MIC＞64μg/ml）及敏感菌株（MIC＜8μg/ml）各15株。用蛋黄平板法培养氟康唑耐药及敏感菌株，测量其产生沉淀圈的大小，计算菌落直径与沉淀圈直径的比值(PZ值)，比较两组间磷脂酶活力的不同。从敏感和耐药菌株中分别选取磷脂酶活力不同的菌株，通过尾静脉注射感染小鼠，以小鼠平均存活时间比较耐药和敏感菌株毒力的不同。结果：15株耐药菌中12株产生特异沉淀圈，PZ值为0.786±0.055；敏感菌株中8株无特异沉淀圈，PZ值为0.913±0.078。耐药组和敏感组小鼠平均存活天数分别为(10.22±2.44)d和(12.83±1.51)d。耐药和敏感菌株磷脂酶活力差异有统计学意义（P＜0.01）；两组小鼠平均存活期差异有统计学意义（P＜0.05）。结论：耐药菌株磷脂酶活力及毒力高于敏感菌株，白念珠菌分泌的细胞外磷脂酶活力及菌株致病性与白念珠菌耐药发生有一定关系。

Correlation of phospholipase activity and virulence of candida albicans between fluconazole-resistant and susceptible strains

Objective: To study the correlation of phospholipase activity and the virulence of candida albicans between fluconazole-resistant and susceptible strains. Methods: NCCLS M27-A protocol was used to assess fluconazole-resistant and susceptible strains. Based on the MIC value, fifteen fluconazole-resistant strains (MIC＞64μg/ml) and fifteen susceptible strains(MIC＜8μg/ml) were obtained from the clinical isolates. These strains were produced by yolk agar. Phospholipase activity of the two groups was compared by the ratio of colony diameter to the total diameter of the colony plus the precipitation zone (PZ). Healthy mice were intravenously injected with the strains with a low or high phospholipase activity. Virulence of Candida albicans between the two groups was assayed by the average survival time of the mice. Results: Twelve of the fluconazole-resistant strains and seven of the fluconazole-susceptible strains produced a distinct precipitation zone implicating phospholipase activity. The value of PZ was 0.786±0.055 and 0.913±0.078, respectively. The average survival times were (10.22±2.44)days and (12.83±1.51)days, respectively. The phospholipase activity and the average survival times between the two groups were significantly different（P＜0.01 and P＜0.05, respectively）. Conclusion: Phospholipase activity and virulence of the fluconazole resistant strains are more active than those of the susceptible strains. Phospholipase activity and virulence of Candida albicans are related to resistance.