Effection Of Extracellular Hydrolytic Enzymes And Drug Resistance On Pathogenicity By Candida Albicans Isolates Involved In Respiratory Infections

Objective To investigate the effection of extracelluar phospholipase and cecretory aspartyl proteinases and the gene expression of these two enzymes on pathogenicity in Candida albicans isolates involved in respiratory infections.Methods①Candida albicans isolated from respiratory tract were collected and identified, then grouped as pathogenic and non-pathogenic isolates;②The secretory proteinase activities of 84 strains of Candida albicans isolates were assayed by the medium containing bovine serum albumin,The extracellular phospholipase activities were tested by means of the egg-yelk-containing plates;③The minimum inhibitory concentrations(MIC) of isolates to fluconzole and itraconazole were detected through the M27-A broth microdilution method recommended by NCCLS;④The gene expression of PLB1 and SAP2 were semi-quantified by RT-RCR.The differences of these results were analyzed between pathogenic and non-pathogenic isolates.The gene expression of CDR1 and MDR1 were also analyzed by this method.⑤Correlations of these four gene expression were studied.Results 84 isolates were collected, 28 isolates of them were identified as non-pathogenic ones,and others as pathogenic ones.The proteinase activity of pathogenic group was higher than that of non-pathogenic group,while there was no difference in phospholipase activity and drug resistance to fouconzole and itraconazole between these two groups.The PLB1 and SAP2 expression was both higer in pathogenic isolates.No correlation were found between pathogenity and drug resistance;Less isolates has drug resistance to fluconzole than that to itraconazole; that of Positive correlation was found in the expression of MDR1 and PLB1,MDR1 and SAP2 ,PLB1 and SAP2.Conclusion These results indicate that cecretory aspartyl proteinase activity is a putative virulence factor for C albicans in respiratory tract.The overexpression of PLB1 and SAP2 may affects the virulence of the isolates.The level of drug resistance to fluconzole is higher than that of itraconazole;The pathogenity of these isolates has no relationship with drug resistance and related gene expression. There may be some relationship about the regulation of MDR1,PLB1and SAP2 during transcription.