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.