Retrospective identification and characterization of Candida dubliniensis isolates among Candida albicans clinical laboratory isolates from human immunodeficiency virus (HIV)-infected and non-HIV-infected individuals

Fungal opportunistic infections, and in particular those caused by the vari ous Candida species, have gained considerable significance as a cause of mo rbidity and, often, mortality. The newly described species Candida dublinie nsis phenotypically resembles Candida albicans so closely that it is easily misidentified as such. The present study was designed to determine the fre quency at which this new species is not recognized in the clinical laborato ry, to determine the patient populations with which C. dubliniensis is asso ciated, to determine colonization versus infection frequency, and to assess fluconazole resistance. Over a 2-year period, 1,251 isolates that were ini tially identified as C. albicans by a hospital clinical laboratory were ree valuated for C. dubliniensis by inability to grow at 45 degrees C, colony c olor on CHROMagar Candida medium, coaggregation assay with Fusobacterium nu cleatum, and sugar assimilation profiles (API 20C AUX yeast identification system). A total of 15 (1.2%) isolates from 12 patients were identified as C. dubliniensis. Ten of the patients were found to be immunocompromised (th ese included patients with human immunodeficiency virus infection or AIDS, cancer patients receiving chemotherapy, and patients awaiting transplantati on). Thirteen isolates were highly susceptible to fluconazole (MIC, < 0.5 m u g/ml), Three isolates from one patient, genotypically confirmed as the sa me strain, showed variable susceptibility to fluconazole, The first isolate was susceptible, whereas the other two isolates were dose-dependent suscep tible (MIC, 16.0 mu g/ml). These data confirm the close association of C, d ubliniensis with immunocompromised states and that increased fluconazole MI Cs may develop in vivo, This study emphasizes the importance of screening g erm-tube-positive yeasts for the inability to grow at 45 degrees C followed by confirmatory tests in order to properly identify this species.