Candida haemulonii and closely related species at 5 university hospitals in Korea: Identification, antifungal susceptibility, and clinical features

Background. Candida haemulonii, a yeast species that often exhibits antifungal resistance, rarely causes human infection. During 2004-2006, unusual yeast isolates with phenotypic similarity to C, haemulonii were recovered from 23 patients (8 patients with fungemia and 15 patients with chronic otitis media) in 5 hospitals in Korea. Methods. Isolates were characterized using D1/D2 domain and ITS gene sequencing, and the susceptibility of the isolates to 6 antifungal agents was tested in vitro. Results. Gene sequencing of the blood isolates confirmed C. haemulonii group I (in 1 patient) and Candida pseudohaemulonii (in 7 patients), whereas all isolates recovered from the ear were a novel species of which C. haemulonii is its closest relative. The minimum inhibitory concentration (MIC) ranges of amphotericin B, fluconazole, itraconazole, and voriconazole for all isolates were 0.5-32 μg/mL (MIC ₅₀, 1 μg/mL), 2-128 μg/mL (MIC ₅₀, 4 μg/mL), 0.125-4 μg/mL (MIC ₅₀, 0.25 μg/mL), and 0.03-2 μg/mL (MIC ₅₀, 0.06 μg/mL), respectively. All isolates were susceptible to caspofungin (MIC, 0.125-0.25 μg/mL) and micafungin (MIC, 0.03-0.06 μg/mL). All cases of fungemia occurred in patients with severe underlying diseases who had central venous catheters. Three patients developed breakthrough fungemia while receiving antifungal therapy, and amphotericin B therapeutic failure, which was associated with a high MIC of amphotericin B (32 μg/mL), was observed in 2 patients. Conclusions. Candida species that are closely related to C haemulonii are emerging sources of infection in Korea. These species show variable patterns of susceptibility to amphotericin B and azole antifungal agents.