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

Abstract

Background: Candida auris is an emerging, potentially multidrug-resistant pathogen that exhibits clade-specific resistance to fluconazole and also develops resistance to echinocandins and amphotericin B easily. This study analysed 49 C auris isolates for alterations in hotspot-1 and hotspot-2 of FKS1 for the detection of mutations conferring reduced susceptibility to echinocandins. Methods: C auris isolates (n = 49) obtained from 18 immunocompromised patients during June 2016-December 2018 were analysed. Antifungal susceptibility testing was performed by Etest and broth microdilution-based MICRONAUT-AM assay. Mutations in hotspot-1 and hotspot-2 regions of FKS1 were detected by PCR sequencing and fingerprinting of the isolates was done by short tandem repeat typing. Results: The patients had multiple comorbidities/risk factors for Candida spp. infection including cancer/leukaemia/lymphoma/myeloma (n = 16), arterial/central line (n = 17), urinary catheter (n = 17), mechanical ventilation (n = 14) and major surgery (n = 9) and received antifungal drugs as prophylaxis and/or empiric treatment. Seven patients developed C auris candidemia/breakthrough candidemia, nine patients had candiduria with/without candidemia and four patients developed surgical site/respiratory infection. Resistance to fluconazole and amphotericin B was detected in 44 and four isolates, respectively. Twelve C auris isolates from eight patients showed reduced susceptibility to echinocandins. Seven isolates contained hostspot-1 mutations and three isolates from a candidemia patient contained R1354H mutation in hotspot-2 of FKS1. Ten patients died, five were cured, two were lost to follow-up and treatment details for one patient were not available. Conclusions: Our findings describe development of a novel mutation in FKS1 conferring reduced susceptibility to echinocandins in one patient during treatment and unfavourable clinical outcome for many C auris-infected patients.

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 ].…”

“…Interestingly, infection from the urinary tract was successfully cleared due to combination therapy with liposomal AMB and caspofungin. Candiduria due to C. auris was also successfully eradicated by therapy with liposomal AMB in another recent study in an immunocompromised patient [ 18 ]. Since AMB is excreted through the kidneys, these findings suggest that treatment with AMB is an attractive alternative to clear urinary tract infection due to C. auris in hospitalized patients.…”

“…Due to a lower culture positivity and non-specific signs and symptoms of the disease, patients with suspected invasive candidiasis are typically treated empirically with antifungal drugs [ 4 , 9 ]; however, patients receiving systemic antifungals also become susceptible to breakthrough infections with drug-resistant fungal pathogens [ 2 , 10 ]. Several reports have described breakthrough candidemia cases with drug-resistant/multidrug-resistant Candida among hospitalized patients receiving antifungal drugs as prophylaxis or empiric therapy, particularly among patients with hematological malignancies or other conditions compromising their immune defenses [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…This novel yeast is easily transmitted among hospitalized patients as it colonizes the skin/nares, is shed into the environment contaminating hospital surfaces and equipment and can survive even under harsh conditions [ 28 , 29 ]. Like other Candida spp., invasive C. auris infections also occur more easily among colonized patients who are critically ill with prolonged hospitalization and have several comorbidities, particularly diabetes mellitus, respiratory disease or chronic kidney disease as well as indwelling catheters, mechanical ventilation and/or admission in the ICU [ 18 , 27 , 30 , 31 , 32 , 33 , 34 , 35 ]. A systematic review and meta-analysis have reported an over-all mortality rate of nearly 39% among C. auris -infected patients [ 36 ].…”