Ribosomic DNA intergenic spacer 1 region is useful when identifying Candida parapsilosis spp. complex based on high-resolution melting analysis.

The epidemiology of Candida parapsilosis and the closely related species C. orthopsilosis and C. metapsilosis has changed in recent years, justify the need to identify this complex at the species level. In this study we investigate the intergenic spacer 1 (IGS1) of the ribosomal DNA (rDNA) to evaluate the utility of this gene region as a phylogenetic molecular marker and the suitability of a high-resolution melting (HRM) strategy based on this region for identification of members of the C. parapsilosis spp. complex. We sequenced the IGS1 and the internal transcribed spacer (ITS) regions of the rDNA from 33 C. parapsilosis sensu lato strains. Although both regions are useful in identifying species, comparative sequence analysis showed that the diversity in the IGS1 region was higher than in the ITS sequences. We also developed an HRM analysis that reliably identifies C. parapsilosis spp. complex based on the amplification of 70 bp in the IGS1 region. All isolates were correctly identified with a confidence interval >98%. Our results demonstrate that HRM analysis based on the IGS1 region is a powerful tool for distinguishing C. parapsilosis from cryptic species.