The drug resistance of Candida albicans biofilm and the correlation of als3 gene expression and film forming

Abstract

Objective To observe the biofilm structure, drug resistance and related gene expressions of clinically collected drug sensitive strains of Candida albicans, and to explore preliminarily the film-forming related gene expressions of Candida albicans. Methods A total of 108 strains of Candida albicans from positive blood culture were obtained from Tianjing First Central Hospital from January to December in 2015 and 58 stains which were sensitive to azole drugs were selected. Sterile indwelling catheter was used to establish the Candida albicans biofilm in vitro model. The structure of Candida albicans biofilm was observed with inverted microscope. The ultrastructure was observed with transmission electron microscope. The drug sensitivity was detected by using trace liquid dilution M27-A2 scheme and the als3, xog, bg1, efg1 gene expressions were detected using polymerase chain reaction method. Paired t test was used for data analysis. Results After Candida albicans biofilm model was set up, Candida albicans cells gathering along the hyphae and forming different layers of membrane structure were observed under inverted microscope. The thickened Candida albicans cell membranes with increased mitochondria and cell activity were observed under transmission electron microscope. Drug resistances to fluconazole, voriconazole and itraconazole were increased after the biofilm formation. The minimal inhibitory concentration values of echinocandins, including caspofungin and micafungin increased at different degree, but did not achieve drug resistance. The als3 gene expressions among strains before biofilm formation were different. Candida albicans with high als3 gene expression tended to form biofilm (t=3.645, P 0.05). Conclusions Drug resistances to fluconazole, voriconazole and itraconazole increase after the Candida albicans biofilm formation. But Candida albicans remains sensitive to echinocandins after the formation of biofilm. The expression of als3 gene can be used to screen Candida albicans which tends to form biofilm. Key words: Candida albicans; Biofilms; Drug resistance; Gene expression profiling; als3