Research On The Correlation Between Secreted Aspartyl Proteinase And The Resistance To Itraconazole Of Candida Albicans

Objective:1. Use BSA agar medium to detect the Sap activity differences of drug-resistance strains and sensitive strains of Candida albicans.2. Compare the virulence and pathogenicity difference of drug resistant and sensitive strains of Candida albicans by animal experiment.3. Compare the difference of SAP2、CDR1、CDR2、MDR1 m RNA expression between drug resistant and sensitive strains of Candida albicans by RT-PCR. Methods:1. Collect the clinical fungal specimens, and isolate, culture and identify itraconazole resistant strains and sensitive strains of Candida albicans. Use BSA agar medium to detect the Sap activity differences of drug resistant and sensitive strains of Candida albicans, and make statistical analysis.2. The mice were randomly divided into 3 groups(itraconazole-resistant group, itraconazole-sensitive group and blank control group). Inject bacteria suspension of Candida albicans both itraconazole-resistant and itraconazole-susceptible strains into the caudal vein of mice(one fungus for one mouse), and inject saline into blank control group. After a month of observation, count survival days of mice and calculate mortality and survival rates of three groups.3. Compare the difference of SAP2、CDR1、CDR2 and MDR1 m RNA expression between drug resistant and sensitive strains of Candida albicans by RT-PCR,and make statistical analysis. Results:1. A total of 40 strains of Candida albicans were detected, incluing 20 strains of itraconzole resistant strains and 20 strains of itraconzole sensitive strains. Both 20 itraconazole-resistant strains and 20 itraconazole-susceptible strains produced specific transparent ring, and the Pz values of itraconazole-resistant and itraconazole-susceptible groups were 0.611±0.015 and 0.667±0.015 respectively. By t test, Sap activity between the two groups was significantly different( t=11.935, P<0.001).2. Animal experiments showed that, within one month, the mice in the blank control group without death,16 mice died in itraconazole-resistant group and 7 mice died in itraconazole-susceptible group and mortality was 80% and 35% respectively. By chi-square test, there was significant difference between itraconazole-resistant and itraconazole-susceptible group in mortality(2c =8.286, P=0.004). By Log-Rank test, there was significant difference between itraconazole-resistant and itraconazole-susceptible group in the survival rate(2c =9.362, P=0.002). Virulence and pathogenicity of itraconazole-resistant strains were higher than that of itraconazole-susceptible strains.3. Expression of SAP2 of itraconazole-resistant group(2.015±0.304) is higher than that of susceptible-group(0.732±0.215). By t test, SAP2 expression between the two groups was significantly different(t=15.425, P<0.001).Comparing CDR1,CDR2 and MDR1 expression of itraconazole-resistant group with that of susceptible-group, there was no significant difference. There exists a highly significant positive correlation between the m RNA levels of SAP2 and the MDR1(r =0.696, P<0.001), so does the m RNA level of CDR1 and CDR2(r=0.837, P<0.001). Conclusion:1. Sap activity of itraconazole-resistant strains of Candida albicans are higher than that of itraconazole-susceptible strains.2. Virulence and pathogenicity of itraconazole-resistant strains of Candida albicans are higher than that of itraconazole-susceptible strains.3. SAP2 gene expression of itraconazole-resistant strains of Candida albicans are higher than that of itraconazole-susceptible strains. SAP2 and MDR1 gene may be subject to the same regulatory mechanism; so may CDR1 and CDR2 gene. There is a certain correlation between SAP2 high expression of Candida albicans and its resistance to itraconazole.