Increasing Prevalence of Multidrug-ResistantCandida haemuloniiSpecies Complex among All Yeast Cultures Collected by a Reference Laboratory over the Past 11 Years

There is worldwide concern with the increasing rates of infections due to multiresistantCandidaisolates reported in tertiary medical centers. We checked for historical trends in terms of prevalence rates and antifungal susceptibility of theCandida haemuloniispecies complex in our yeast stock culture collected during the last 11 years. The isolates were identified by sequencing the rDNA internal transcribed spacer (ITS) region, and antifungal susceptibility tests for amphotericin B, voriconazole, fluconazole, anidulafungin, and 5-fluorocytosine were performed by the Clinical and Laboratory Standards Institute (CLSI) microbroth method. A total of 49 isolates were identified asCandida haemuloniisensu stricto(n= 21), followed byC. haemuloniivar.vulnera(n= 15) andC. duobushaemulonii(n= 13), including 38 isolates cultured from patients with deep-seatedCandidainfections. The prevalence of theC. haemuloniispecies complex increased from 0.9% (18 isolates among 1931) in the first period (December 2008 to June 2013) to 1.7% (31 isolates among 1868) in the second period (July 2014 to December 2019) of analysis (p= 0.047). All isolates tested exhibited high minimum inhibition concentrations for amphotericin B and fluconazole, but they remained susceptible to 5-fluorocytosine and anidulafungin. We were able to demonstrate the increased isolation of the multiresistantCandida haemuloniispecies complex in our culture collection, where most isolates were cultured from patients with deep-seated infections.