Differentiation of Candida albicans complex species isolated from invasive and non-invasive infections using HWP1 gene size polymorphism

Background and Purpose: The taxonomy of Candida is controversial and has undergone changes due to the investigation of the novel species. Candida africana and Candida dubliniensis are new members of C. albicans complex that are currently gaining both clinical and epidemiologic significance. This study reports the prevalence of C. africana among the strains isolated from patients, by using HWP1 gene size polymorphism. Materials and Methods: A total of 235 yeasts confirmed as C. albicans complex based on chromogenic media and ITS-sequencing isolated from various clinical forms of invasive and non-invasive candidiasis mainly candidemia, were re-identified based on HWP1 gene polymorphisms. The Hwp1-PCR amplicons were re-confirmed by sequencing and BLAST analysis. Results: Based on the HWP1 gene size polymorphism, 223 strains were identified as C. albicans (94.89%) from which 7 isolates produced two DNA fragments (850 and 941 bp). C. dubliniensis (n=4, 1.7%), C. africana (n=1, 0.42%) and mix of C. albicans and C. africana (n=7, 2.97%) were also identified. Conclusion: Although C. albicans remains the most common Candida species, C. dubliniensis and C. africana are rarely found among the patient isolates. Due to limited information on the molecular epidemiology of this novel yeast, more studies using molecular methods are recommended.

Extreme diversification driven by parallel events of massive loss of heterozygosity in the hybrid lineage of Candida albicans

Candida albicans is the most commonly reported species causing candidiasis. The taxonomic classification of C. albicans and related lineages is controversial, with Candida africana (syn. C. albicans var. africana) and Candida stellatoidea (syn. C. albicans var. stellatoidea) being considered different species or C. albicans varieties depending on the authors. Moreover, recent genomic analyses have suggested a shared hybrid origin of C. albicans and C. africana, but the potential parental lineages remain unidentified. Although the genomes of C. albicans and C. africana have been extensively studied, the genome of C. stellatoidea has not been sequenced so far. In order to get a better understanding of the evolution of the C. albicans clade, and to assess whether C. stellatoidea could represent one of the unknown C. albicans parental lineages, we sequenced C. stellatoidea type strain (CBS 1905). This genome was compared to that of C. albicans and of the closely related lineage C. africana. Our results show that, similarly to C. africana, C. stellatoidea descends from the same hybrid ancestor as other C. albicans strains and that it has undergone a parallel massive loss of heterozygosity.