Identification of Candida dubliniensis among oral yeast isolates from an italian population of human immunodeficiency virus-infected (HIV +) subjects

Abstract

Candida dubliniensis, an emerging oral pathogen, phenotypically resembles Candida albicans so closely that it is easily misidentified as such. The aim of the present study was to evaluate the usefulness of two phenotypic methods, growth at 45°C and 2,3,5-triphenyltetrazolium chloride (TTC) reduction, for confirming presumptive identification of C. dubliniensis and C. albicans by colony color on CHROMagar Candida (CAC) medium. A combination of these methods was used to establish the prevalence of oral C. dubliniensis in an Italian population of 45 human immunodeficiency virus (HIV)-infected subjects. Twenty-two samples (48.9%) were positive for yeasts on CAC medium producing a total of 37 fungal isolates. The colony color and 45°C growth ability test correctly identified all C. dubliniensis and C. albicans isolates (5/37, 13.5%, and 16/37, 43.2%, respectively), while assessment of TTC reduction misidentified one C. albicans isolate. The isolation rate of C. dubliniensis was 11.1% (5/45 patients). All of the C. dubliniensis isolates were highly susceptible to fluconazole (MIC = 0.5 μg/ml). The combination of CAC medium screening with growth at 45°C and TTC reduction tests may represent a simple, reliable and inexpensive identification protocol for C. dubliniensis.