Abstract:

Objective To investigate the performance of DNA microarray in identifying 6 common Candida spp. and validating ERG11 mutations resulting in fluconazole-resistance in Candida albicans. Methods Oligonucleotide probes were designed and synthesized targeting the species-specific sequence in the internal transcribed spacer 2 （ITS2） region of rDNA of Candida albicans, Candida tropicalis, Candida glabrata, Candida dubliniensis, Candida parapsilosis and Candida krusei, as well as 6 sequences embracing the following mutations respectively in ERG11 gene leading to fluconazole-resistance, i.e., T541C, A1090G, C1361T, G1537A, G1547A, and T1559C, then arranged onto a chip. Twelve 50-base-pair oligonucleotides were artificially synthesized based on the above specific sequences, and utilized to hybridize with the DNA microarray. Thirty-four Candida strains, including 29 C. albicans, 1 Candida tropicalis, 1 Candida glabrata, 1 Candida dubliniensis, 1 Candida parapsilosis and 1 Candida krusei, were detected with microarray. Genomic DNA was extracted from these tested strains and underwent multiple PCR for the amplification of ITS2 region and ERG11 gene. Sequencing was performed to analyze the sequence of ERG11 in 29 strains of C. albicans and the results were compared with those of DNA microarray hybridization. Results Multiple PCR successfully produced ITS2 fragment of 307-415 bp from all the 34 strains, as well as ERG11 fragment of 1712 bp from 29 C. albicans strains. DNA microarray hybridization offered the same results in species identification of the 34 strains with their given information, as well as in mutation detection of the 29 strains of C. albicans with ERG11 sequencing results. Also, the 6 synthesized oligonucleotides containing the mutations were identified precisely as T541C, A1090G, C1361T, G1537A, G1547A, and T1559C, and the 6 species specific oligonucleotieds were identified correctly as C. albicans, C. tropicalis, C. glabrata, C. dubliniensis, C. parapsilosis and C. krusei. Both the sensitivity and the specificity of the microarray were 100%. Conclusion DNA microarray is a quite reliable method to identify Candida spp. and fluconazole resistance-associated mutations in the ERG11 gene of C. albicans.

Key words: DNA array;Candida;Identification;Mutation;ERG11