Candida nivariensis, an emerging pathogenic yeast with multi-drug resistance to antifungal agents

Mycology Reference Laboratory, Health Protection Agency, Bristol, Department of Pathology and Microbiology, University of Bristol, and British Antarctic Survey, Cambridge, United Kingdom

^* To whom correspondence should be addressed. Email: Andy.Borman{at}ubht.nhs.uk.

	Abstract

In 2005, Candida nivariensis, a yeast species genetically related to Candida glabrata, was described following its isolation from 3 patients in a single Spanish hospital. Between 2005-2006, 16 yeast isolates with phenotypic similarities to C. nivariensis were submitted to the UK Mycology Reference Laboratory for identification. The strains originated from various clinical specimens, including deep, usually sterile sites, from patients at 12 different UK hospitals. PCR amplification and sequencing of the D1D2 and ITS1 regions of the nuclear ribosomal gene cassette confirmed that these UK isolates are genetically identical to C. nivariensis. Biochemically, C. glabrata and C. nivariensis are distinguished by their differential ability to assimilate trehalose. However, in contrast to the original published findings, we found that C. glabrata isolates, but not C. nivariensis, are capable of assimilating this substrate. Antifungal susceptibility tests revealed C. nivariensis isolates to be less susceptible than C. glabrata to itraconazole, fluconazole and voriconazole and to have significantly higher MICs to flucytosine than C. glabrata strains. Finally, C. nivariensis could be rapidly distinguished from the other common pathogenic yeast species by pyrosequencing of the ITS2 region. In the light of these data, we believe that C. nivariensis should be regarded as a clinically important emerging pathogenic yeast.