Resumo

Introduction: some studies have discussed the genetic variation in the ribosomal DNA (rDNA) internal transcribed spacer (ITS) within the Fungi Kingdom. However, the levels of ITS sequence polymorphisms among Candida species and their association with acquisition sources of invasive fungal infections remain poorly investigated. Objectives: here, we characterized the intra- and interspecific ITS polymorphisms of Candida spp. isolates collected from patients with bloodstream infections. Material and Methods: we selected 276 Candida strains stored in the yeast culture collection of Laboratório Especial de Micologia – Universidade Federal de São Paulo, during the period of 1997-2011. Complete ITS sequences (ITS1-5.8S-ITS2 regions) were obtained after alignment using Seaview 4.2.12 program with muscle algorithm, and the sequence polymorphisms were analyzed with DnaSP v5.10.1 based on haplotype number, polymorphic sites and haplotype diversity (Hd). The mother program v.1.25.1 was used for calculating the uncorrected p-distance among different haplotypes of Candida within the same species (intraspecific distances), and between ITS sequences from reference strains of Candida spp. (interspecific distances). Results: the analysis of intraspecific ITS variability revealed different haplotypes among 10 Candida species, with more frequent polymorphism in ITS1 than in ITS2. High intraspecific variations were evidenced by large numbers of haplotypes, polymorphic sites and Hd among species related to endogenous sources of infection: C. albicans (Hd=0.7783), C. tropicalis (Hd=0.7500), C. glabrata (Hd= 0.6179) and C. lusitaniae (Hd=0.8571). By contrast, minor intraspecific divergences were observed among isolates of C. parapsilosis (sensu stricto) (Hd=0.2924), C. orthopsilosis (Hd=0.4456) and C. pelliculosa (Hd=0), whose main sources of infection are supposed to be exogenous. The analysis of uncorrected p-distance revealed intraspecific distances (from 0.0013 to 0.0500) clearly lower than the interspecific ones (from 0.0506 to 0.7379). Conclusions: these results demonstrate different patterns of rDNA ITS polymorphisms among Candida spp., suggesting the usefulness of this genetic marker for identification of distinct haplotypes, which might contribute to understand the natural history of bloodstream infections caused by Candida species, and reinforces the application of ITS region as a barcode for clinically relevant fungi.