磷脂酶对新生隐球菌毒力的影响

The Effect of Phospholipase on the Virulence of Cryptococcus neoformans

目的评价不同条件、不同来源和不同血清型的新生隐球菌分泌磷脂酶的情况;观察胞外磷脂酶对菌株毒力的影响。方法分别在30℃和37℃下用蛋黄平板法培养不同来源的40株新生隐球菌,计算沉淀圈比值(PZ值),比较其磷脂酶活力的不同;建立小鼠感染模型,用小鼠的平均生存期及脑组织菌落形成单位(cfu)比较分泌磷脂酶和不分泌磷脂酶菌株毒力的变化。结果39株菌的菌落周围产生明显白色沉淀圈,PZ值在30℃和37℃培养条件下分别为0.529±0.121和0.523±0.143;血清型A、B及AD和D型的PZ值分别为0.541±0.116、0.518±0.036和0.472±0.051;不同温度间和不同血清型组间差异均无显著性(P>0.05);临床株和环境株PZ值分别为0.501±0.049和0.565±0.131,差异有显著性(P<0.05)。感染分泌磷脂酶菌株和不分泌磷脂酶菌株两组小鼠脑组织的cfu分别为518.67±203.86和226.47±196.13,两组小鼠的平均生存期分别为18.90d和26.39d,差异有显著性(P<0.01)。结论温度对新生隐球菌磷脂酶活力没有影响;其中临床分离株比环境分离株磷脂酶活力强;不同血清型菌株的磷脂酶活力无差别;分泌磷脂酶的菌株毒力比不分泌磷脂酶菌株的毒力强。

Objective To evaluate the activity of phospholipase secreted by Cryptococcus neofor-mans from different sources,serotypes and incubation conditions,and to observe the effect of phospholipase on fungal virulence.Methods The extracelluar phospholpase activity was detected in40isolates of C.neo-formans after being incubated onto egg yolk agar.Phospholipase activities of individual isolate were com-pared according to the ratio of colony diameter to the sum of colony diameter plus precipitation zone(PZ).Infected mouse model was established.The virulence of the isolates was observed based on the colony form-ing unit(cfu)in cerebral tissue and the survival time of mice infected by C.neoformans with different phos-pholipase activities.Results Thirty-nine of forty isolates produced distinct precipitation zone on culture media.PZs were0.529±0.121and0.523±0.143at incubation temperature of30℃and37℃,respec-tively.Incubated at37℃,PZs of serotype A,B and AD/D were0.541±0.116,0.518±0.036and0.472±0.051,respectively(P>0.05).PZs of clinical and environmental isolates were0.501±0.049and0.565±0.131,respectively(P<0.05).In vivo,the mean survival time and the cfu in brain were18.90d,518.67±203.86,in mice infected by C.neoformans with extracellular phospholipase activity and26.39d,226.47±196.13,respectively,in those without phospholipase activity(P<0.01).Conclusions The in-cubation temperature has no effect on phospholipase activity.A significant difference of phospholipase activi-ty is found between clinical and environmental isolates,and among isolates of serotype A,B and AD/D.C.neoformans with phospholipase activity exerts stronger virulence in comparison with that without extracelluar phospholipase activity.