title: Target enzyme mutations confer differential echinocandin susceptibilities in Candida kefyr.
abstract: Candida kefyr is an increasingly reported pathogen in patients with hematologic malignancies. We studied a series of bloodstream isolates that exhibited reduced echinocandin susceptibilities (RES). Clinical and surveillance isolates were tested for susceptibilities to all three echinocandins, and those isolates displaying RES to one or more echinocandins were selected for molecular and biochemical studies. The isolates were analyzed for genetic similarities, and a subset was analyzed for mutations in the echinocandin target gene FKS1 and glucan synthase echinocandin sensitivities using biochemical methods. The molecular typing did not indicate strong genetic relatedness among the isolates except for a series of strains recovered from a single patient. Two unrelated isolates with RES had previously uncharacterized FKS1 mutations: R647G and deletion of amino acid 641 (F641Δ). Biochemical analysis of the semipurified R647G glucan synthase generated differential echinocandin sensitivity (resistance to micafungin only), while the deletion of F641 resulted in a glucan synthase highly insensitive to all three echinocandins. The consecutive isolates from a single patient with RES all harbored the common S645P mutation, which conferred resistance to all three echinocandins. The MIC values paralleled the glucan synthase inhibition kinetic data, although the S645P isolates displayed relatively higher susceptibility to caspofungin (2 μg/ml) than the other two echinocandins (>8 μg/ml). These findings highlight novel and common FKS1 mutations in C. kefyr isolates. The observation of differential susceptibilities to echinocandins may provide important mechanistic insights for echinocandin antifungals.
authors: Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA.
authors: Janet F
authors: JF
authors: Staab
authors: Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA.
authors: Dionysios
authors: D
authors: Neofytos
authors: Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA.
authors: Peter
authors: P
authors: Rhee
authors: Public Health Research Institute, New Jersey Medical School-Rutgers University, Newark, New Jersey, USA.
authors: Cristina
authors: C
authors: Jiménez-Ortigosa
authors: Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA.
authors: Sean X
authors: SX
authors: Zhang
authors: Public Health Research Institute, New Jersey Medical School-Rutgers University, Newark, New Jersey, USA.
authors: David S
authors: DS
authors: Perlin
authors: Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA The Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland, USA kmarr4@jhmi.edu.
authors: Kieren A
authors: KA
authors: Marr
mesh_terms: D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000494:pharmacology; D002175:Candida / Q000187:drug effects* / Q000235:genetics*; D000077336:Caspofungin; D025141:Drug Resistance, Fungal / Q000187:drug effects / Q000235:genetics; D054714:Echinocandins / Q000494:pharmacology*; D005656:Fungal Proteins / Q000235:genetics; D005964:Glucosyltransferases / Q000235:genetics; D006801:Humans; D055666:Lipopeptides / Q000494:pharmacology; D000077551:Micafungin; D008826:Microbial Sensitivity Tests / Q000379:methods; D008969:Molecular Sequence Data; D009154:Mutation / Q000187:drug effects* / Q000235:genetics*; D020539:Sequence Analysis, Protein
chemical_list: D000935:Antifungal Agents; D054714:Echinocandins; D005656:Fungal Proteins; D055666:Lipopeptides; D005964:Glucosyltransferases; C040232:glucan synthase; D000077336:Caspofungin; D000077551:Micafungin