氧化剂体外诱导对阿萨希毛孢子菌致病性影响的实验研究

Experimental study on the pathogenicity of Trichosporon asahii induced by oxidant in vitro

目的观察比较2种氧化剂H2O2、甲萘醌体外诱导前后阿萨希毛孢子菌致病性的变化。方法将T.asahii CBS2479、CBS8904分别在H2O2、甲萘醌浓度逐渐梯级倍增的YPD液体培养基中传代,直至不再生长。将诱导前菌株及诱导终末代菌株分别感染免疫缺陷小鼠(BALB/c裸鼠),计算各组小鼠的半数致死量LD50,记录各组小鼠的生存时间,绘制生存曲线。结果2种氧化剂诱导后菌株的半数致死量均显著低于未诱导组,其中环境株CBS 8904甲萘醌诱导后菌株的半数致死量较未诱导菌株降低1.5个数量级(47倍),而临床株CBS 2479甲萘醌诱导后菌株的半数致死量较未诱导菌株低1个数量级(10倍)。生存曲线分析结果显示,氧化剂诱导后的临床株(菌株3和菌株2)两组所有小鼠分别在第9天、第11天全部死亡,生存率是0%,而未诱导组(菌株1)小鼠在第9天时生存率是50%;氧化剂诱导后的环境株(菌株6和菌株5)两组小鼠在第11天的生存率分别20%和60%,而未诱导组(菌株4),在第11天时生存率是70%。结论两种氧化剂诱导后菌株的半数致死量显著降低,感染小鼠的生存率明显下降,的致病性显著升高。

Objective To observe and compare the changes of pathogenicity of Trichosporon asahii(T.asahii)before and after the induction of two oxidants hydrogen peroxide(H2O2)and methylnaphthoquinone in vitro.Methods T.asahii CBS 2479 and CBS 8904 were subcultured in YPD liquid medium with stepwise doubling of the concentration of H2O2 and methylnaphthoquinone until T.asahii stopped growing.Immunodeficiency mice(BALB/c nude mice)were infected with pre-induction strains and final-generation strains respectively.The LD50 of each group was calculated.The survival time of each group was recorded and the survival curve was drawn.Results The LD50 of strains induced by two oxidants was significantly lower than that of non-induced group,of which the LD50 of T.asahii strain CBS 8904 induced by methylnaphthoquinone was 1.5 orders of magnitude(47 times)lower than that of non-induced strain,while that of clinical strain CBS 2479 was 10 times lower than that of non-induced strain.Survival curve analysis showed that all mice infected by oxidant-induced clinical strain 3 and strain 2 died before the 9th and 11th day respectively,and the survival rate was 0%,while that of non-induction group(strain 1)was 50% on the 9th day.For the mice infected by oxidant-induced environmental strain(strain 6 and strain 5),the survival rates were 20% and 60%respectively,while the survival rate was 70%on the 11th day in the non-induction group(strain 4).Conclusion The LD50 of T.asahii strain induced by two oxidants was significantly reduced,the survival rate of infected mice was significantly decreased,and the pathogenicity of T.asahii was significantly increased.