Impact of FKS1 Genotype on Echinocandin In Vitro Susceptibility in Candida auris and In Vivo Response in a Murine Model of Infection

Abstract

Objectives: Echinocandins are frontline antifungal agents in the management of invasive infections due to multi-drug resistant Candida auris . The study aimed to evaluate echinocandin resistance in C. auris isolates of multicentric origin, identify the resistance mechanism, and analyze the pharmacodynamic response to caspofungin in a neutropenic mouse model of infection. Methods : A total of 199 C. auris isolates originating from thirty centres across India were tested for susceptibility to echinocandins. Isolates with reduced susceptibility were evaluated for FKS 1 mutations and in-vivo response to caspofungin in a murine model of disseminated candidiasis. In addition, the response to echinocandins was assessed in light of in-vitro growth kinetics, chitin content; and transcript levels of chitin synthase and FKS1 genes. Results: We report 10 resistant C. auris isolates with four FKS 1 mutations: F635Y ( n =2), F635L ( n =4), S639F ( n =3), and R1354S ( n =1). Of these, F635Y and R1354S exhibited the most profound resistance in mouse model of disseminated infection. S639F and F635L mutations conferred a moderate in vivo resistance, whereas wild-type isolates exhibiting borderline MIC were susceptible in vivo . FKS 1 genotype was more accurate predictor of in-vivo response than the MIC of the isolates. Isolates with high basal or inducible chitin content exhibited higher in vitro MIC in FKS 1 mutant compared to wild-type. Conclusions FKS 1 mutations play a major role in clinically relevant echinocandin resistance in C. auris with differential in vivo outcomes. This study could have implications for clinical practice and, therefore, warrants further studies.

Molecular characterisation of Candida auris isolates from immunocompromised patients in a tertiary‐care hospital in Kuwait reveals a novel mutation in FKS1 conferring reduced susceptibility to echinocandins

“…Furthermore, C auris with R1354S mutation showed more profound resistance to echinocandins than isolates with S639F or S639L mutation in the mouse model of disseminated infection. 80 Patient P11 also with multiple myeloma received caspofungin prophylaxis from 27.11.2017 to 11.12.2017 and then again from Although two C auris isolates with S639F mutation yielded lower MIC values of 2 and 4 µg/ml compared to three other isolates with the same mutation yielding MIC value of 8 µg/ml, the essential agreement (±2 dilutions), similar to another study, 71 was 100%.…”

“…29,78,79 Also the presence of identical FKS1 mutation (R1354H) in colonising strains and subsequently in the bloodstream isolate suggests that candidemia likely resulted due to translocation of the yeast from the respiratory tract in this patient. Very recently, Sharma et al 80 have also reported a non-synonymous (R1354S) mutation at the same codon position in hotspot-2 region of FKS1 in one of 10…”

“…[77][78][79]81,82 Sharma et al 80 have also recently concluded that the FKS1 genotype is a more accurate predictor of in vivo response to treatment than the MICs of the C auris isolates to echinocandins based on increased resistance of C auris with F635Y or R1354S mutation compared to isolates with S639F or S639L mutation to echinocandins in the mouse model of disseminated infection. 80 Two C auris isolates with reduced susceptibility to micafungin from two other (P3 and P12) patients contained wild-type sequences for both hotspot-1 and hotspot-2 regions of FKS1. It is probable that the molecular basis of reduced susceptibility to micafungin in these isolates, similar to C glabrata, involves genetic alterations in hotspot-1 of FKS2 29,78,79 or in other regions of FKS genes.…”

Fatal Breakthrough Candidemia in an Immunocompromised Patient in Kuwait Due to Candida auris Exhibiting Reduced Susceptibility to Echinocandins and Carrying a Novel Mutation in Hotspot-1 of FKS1

“…The bloodstream isolate was resistant to the fluconazole but exhibited a reduced susceptibility (MIC 0.125 µg/mL) to micafungin while the four colonizing strains obtained previously were resistant to fluconazole but were highly susceptible (MIC 0.016 µg/mL) to micafungin. Furthermore, unlike the four colonizing strains which contained the wild-type sequence, the bloodstream isolate displayed a novel mutation (S639T) in hotspot-1 of FKS1 which has not been described previously among echinocandin-resistant C. auris [ 18 , 34 , 43 , 45 , 46 , 47 , 48 ]. Although the C. auris isolate recovered from the tracheal aspirate one day later also exhibited a reduced susceptibility (MIC 1 µg/mL) to micafungin, it contained an S639Y mutation in hotspot-1 of FKS1 while another C. auris isolate from the tracheal aspirate recovered three days later was similar to the bloodstream isolate in terms of both susceptibility to micafungin (MIC 0.125 µg/mL) and the FKS1 sequence (S639T mutation in hotspot-1 of FKS1 ).…”

“…Fluconazole resistance-conferring mutations in ERG11 were detected by PCR-sequencing, as described previously [ 45 ]. The mutations conferring resistance to micafungin in C. auris strains are usually located in the hotspot-1 or hotspot-2 regions of the FKS1 gene [ 18 , 28 , 46 ]. Mutations in the hotspot-1 and hotspot-2 regions of FKS1 were detected by PCR-sequencing, as described previously [ 18 , 45 ].…”