Emergence of a truly multidrug-resistant Candida kefyr (Kluveromyces marxianus) in Kuwait. Multidrug-resistant C. kefyr in Kuwait

Background: Candida kefyr, an emerging multidrug-resistant yeast, causes invasive candidiasis in susceptible patients. This study determined the prevalence of C. kefyr among yeast isolates collected during 2011-2018 in Kuwait. Antifungal susceptibility testing (AST) and genotypic heterogeneity among C. kefyr was also studied. Methods: C. kefyr isolates were identified by CHROMagar Candida, Vitek 2 and PCR amplification of rDNA. Genotypic heterogeneity was determined with microsatellite-/minisatellite-based primers and by PCR-sequencing of IGS1 region of rDNA. AST was performed by Etest. Molecular basis of resistance to fluconazole was studied by PCR-sequencing of ERG11. Findings: Among 8257 yeast strains, 69 C. kefyr (including four bloodstream and seven other invasive) isolates were detected by phenotypic and molecular methods. Isolation from urine and respiratory samples from female and male patients was significantly different (P=0.001). Fingerprinting with microsatellite-/minisatellite-based primers apparently identified only three types. IGS1 sequencing identified seven haplotypes among 27 selected isolates. Four isolates showed reduced susceptibility to amphotericin B (AMB) and one isolate to all (AMB, fluconazole, voriconazole and caspofungin/micafungin) antifungals tested. Fluconazole-resistant isolate contained wild-type Erg11 protein.Conclusions: Although frequency of isolation of invasive and non-invasive C. kefyr was stable during the study period, four of five isolates with reduced susceptibility to antifungals were obtained during last four years indicating increasing trend of reduced susceptibility to antifungals. The invasive and AMB-resistant isolates were genotypically heterogeneous.