Antifungal Resistance Trends of Candida auris Clinical Isolates, New York-New Jersey, 2016-2020

About 55% of U.S. Candida auris clinical cases were reported from New York and New Jersey from 2016 through 2020. Nearly all New York-New Jersey clinical isolates (99.8%) were fluconazole resistant, and 50% were amphotericin B resistant. Echinocandin resistance increased from 0% to 4% and pan-resistance increased from 0 to <1% for New York C. auris clinical isolates but not for New Jersey, highlighting the regional differences.

Molecular epidemiology of Candida auris in Qatar using whole genome sequence data

Candida auris is an emerging, multidrug resistant fungal pathogen that has become a public health threat worldwide. Candida auris spreads easily among patients within and between hospitals, and the incidence of infections has increased substantially in the last decade. Multiple C. auris outbreaks have been reported worldwide including India, USA and United Kingdom. Infections and outbreaks caused by C. auris have also been reported in the Middle East region including Kuwait, Oman, Saudi Arabia, and Qatar; however, the origin of these isolates is largely unknown. This study uses whole genome sequencing (WGS) data to determine the epidemiology and the drug resistance mutations from C. auris in Qatar. Forty samples isolated from the patients and the hospital environment were sequenced by Illumina Nextseq. Core genome SNPs revealed that all isolates belonged to the Indian lineage, which could be originated from the expatriate labour from South Asia. The genetic variability among the isolates was low but comprised of more than one genetic cluster. The environmental isolates were identical to the clinical isolates, and the isolates from patients of different hospitals/outbreaks clustered together, suggesting the transmission of C. auris could be linked to infected/colonized patients and the hospital environment. Mutations associated with azole and echinocandin resistance were discussed.

Case Report: Echinocandin-Resistance Candida glabrata FKS Mutants From Patient Following Radical Cystoprostatectomy Due to Muscle-Invasive Bladder Cancer

Invasive Candida glabrata infections are not common complications after radical cystoprostatectomy. Furthermore, resistance to echinocandins arising during the course of a patient’s treatment is rarely recognised. We described a case of development of echinocandin resistance in a patient with muscle-invasive bladder cancer (pT2b N0 M0, high grade) diagnosis, subjected to radical cystoprostatectomy and exposed to echinocandins. A male patient with a previous surgical history after a traffic accident, who was operated on due to bladder cancer, underwent an episode of candidemia and mixed postoperative wound and urinary tract infection caused by C. glabrata and extended spectrum β-lactamase (ESBL)-producing Escherichia coli during hospital treatment. The patient was started on caspofungin. Repeat blood cultures showed clearance of the bloodstream infection; however, infection persisted at the surgical site. Resistance to echinocandins developed within 2 months from the day of initiation of therapy with caspofungin in the C. glabrata strain obtained from the surgical site. The isolates sequentially obtained during the patient’s treatment demonstrated resistance to echinocandins due to the mutation in hotspot 1 FKS2. Although resistance to echinocandins is relatively rare, it should be considered in oncological patients with increased complexity of treatment and intestinal surgery.

Prevalence of Antifungal Resistance, Genetic Basis of Acquired Azole and Echinocandin Resistance, and Genotyping of Candida krusei recovered from an International Collection

This study was designed to evaluate the prevalence of antifungal resistance, genetic mechanisms associated with in vitro induction of azole and echinocandin resistance and genotyping of Candida krusei , which is intrinsically resistant to fluconazole and is recovered from clinical and non-clinical sources from different countries. Our results indicated that all the isolates were susceptible or had the wild phenotype (WT) to azoles, amphotericin B, and only 1.27% showed non-WT for flucytosine. Although 70.88% of the isolates were resistant to caspofungin, none of them were categorized as echinocandin-resistant as all were susceptible to micafungin and no FKS1 hotspot 1 (HS1) or HS2 mutations were detected. In vitro induction of azole and echinocandin resistance confirmed the rapid development of resistance at low concentrations of fluconazole (4 μg/ml), voriconazole (0.06 μg/ml) and micafungin (0.03 μg/ml), with no difference between clinical and non-clinical isolates in the resistance development. Overexpression of ABC1 gene and FKS1 HS1 mutations were the major mechanisms responsible for azole and echinocandin resistance, respectively. Genotyping of our 79 isolates coupled with 217 other isolates from different sources and geography confirmed that the isolates belong to two main subpopulations, with isolates from human clinical material and Asia being more predominant in cluster 1, and environmental and animals isolates and those from Europe in cluster 2. Our results are of critical concern, since realizing that the C. krusei resistance mechanisms and their genotyping are crucial for guiding specific therapy and for exploring the potential infection source.

Emerging Echinocandin Resistance – A Review

Worldwide there is a steady increase in the number of fungal infections each year. Simultaneously, there is a high rise of antifungal resistance among the Candida isolates. This has now become a major concern in hospitalized patients resulting in poor treatment outcome. Echinocandins, a new group of antifungals has given promising results inspite of its increasing rate of resistance exhibited by some Candida species.

Impact of FKS 1 genotype on echinocandin in-vitro susceptibility in Candida auris and in -vivo response in a murine model of infection

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.

Antifungal Susceptibility Profiles and Resistance Mechanisms of Clinical Diutina catenulata Isolates With High MIC Values

Diutina catenulata (Candida catenulata) is an ascomycete yeast species widely used in environmental and industrial research and capable of causing infections in humans and animals. At present, there are only a few studies on D. catenulata, and further research is required for its more in-depth characterization and analysis. Eleven strains of D. catenulata collected from China Hospital Invasive Fungal Surveillance Net (CHIF-NET) and the CHIF-NET North China Program were identified using matrix-assisted laser desorption ionization–time of flight mass spectrometry and internal transcribed spacer sequencing. The antifungal susceptibility of the Diutina catenulata strains was tested using the Clinical and Laboratory Standards Institute broth microdilution method and Sensititre YeastOne™. Furthermore, ERG11 and FKS1 were sequenced to determine any mutations related to azole and echinocandin resistance in D. catenulata. All isolates exhibited low minimum inhibitory concentration (MIC) values for itraconazole (0.06–0.12 μg/ml), posaconazole (0.06–0.12 μg/ml), amphotericin B (0.25–1 μg/ml), and 5-flucytosine (range, &lt;0.06–0.12 μg/ml), whereas four isolates showed high MICs (≥4 μg/ml) for echinocandins. Strains with high MIC values for azoles showed common ERG11 mutations, namely, F126L/K143R. In addition, L139R mutations may be linked to high MICs of fluconazole. Two amino acid alterations reported to correspond to high MIC values of echinocandin, namely, F621I (F641) and S625L (S645), were found in the hot spot 1 region of FKS1. In addition, one new amino acid alteration, I1348S (I1368), was found outside of the FKS1 hot spot 2 region, and its contribution to echinocandin resistance requires future investigation. Diutina catenulata mainly infects patients with a weak immune system, and the high MIC values for various antifungals exhibited by these isolates may represent a challenge to clinical treatment.

Two Sequential Clinical Isolates of Candida glabrata with Multidrug-Resistance to Posaconazole and Echinocandins

Candida glabrata is one of the most prevalent causative pathogens of invasive candidiasis, and multidrug-resistant strains are emerging. We identified two clinical isolates of C. glabrata, BMU10720 and BMU10722 sequentially isolated from one patient with multidrug-resistance to posaconazole (POS), caspofungin (CAS), micafungin (MCF), and anidulafungin (ANF). Overexpression of ERG11 in BMU10720 and CDR1 in BMU10722 were detected at basal level. When exposed to POS, CDR1 was significantly up-regulated in both isolates compared with susceptible reference strain, while ERG11 was up-regulated considerably only in BMU10720. PDR1 sequencing revealed that both isolates harbored P76S, P143T, and D243N substitutions, while ERG11 was intact. Cdr1 inhibitor FK520 reversed POS-resistance by down-regulating ERG11 expression. FKS sequencing revealed that both isolates harbored S663P substitution in FKS2, and four single nucleotide polymorphisms (SNPs) existed in FKS2 genes between BMU10720 and BMU10722, while FKS1 was intact. Both FKS1 and FKS2 were up-regulated by CAS in BMU10720 and BMU10722. FK520 down-regulated FKS2 expression induced by CAS through inhibiting calcineurin, resulting in synergic effect with echinocandins as well as Congo Red and Calcofluor White, two cell wall-perturbing agents. In conclusion, the multidrug-resistance of C. glabrata isolates in our study was conferred by different mechanisms. CDR1 and ERG11 overexpression in one isolate and only CDR1 overexpression in the other isolate may mediate POS-resistance. S663P mutation in FKS2 and up-regulation of FKS2 may contribute to echinocandin-resistance in both isolates.

Antifungal susceptibility testing identifies the abdominal cavity as a source of Candida glabrata resistant isolates

To identify unrecognized niches of resistant Candida isolates and compartmentalization we retrospectively studied the antifungal susceptibility of 1,103 Candida spp. isolates from blood cultures, non-blood sterile samples, and non-sterile samples. Antifungal susceptibility was assessed by EUCAST E.Def 7.3.2; sequencing and genotyping of the FKS1-2 and ERG11 genes were carried out for non-wild type isolates. Resistance compartmentalization (presence of resistant and susceptible isogenic isolates in different anatomical sites of a given patient) was studied. Clinical charts of patients carrying non-wild type isolates were reviewed. Most isolates (63%) were Candida albicans , regardless the clinical source; Candida glabrata (27%) was the second most frequently found species in abdominal cavity samples. Fluconazole and echinocandin resistance rates were 1.5% and 1.3%, respectively, and highest in C. glabrata . We found 22 genotypes among non-wild type isolates, none of them widespread across the hospital. Fluconazole/echinocandin resistance rates of isolates from abdominal cavity (3.2%/3.2%) were significantly higher than those from blood cultures (0.7%/1.3%) ( P <0.05). Overall, fifteen patients with different forms of candidiasis were infected by resistant isolates, 80% of whom had received antifungals before or at the time of isolate collection; resistance compartmentalization was found in six patients, mainly due to C. glabrata . The highest antifungal resistance rate was detected in isolates from the abdominal cavity, mostly C. glabrata . Resistance was not caused by the spread of resistant clones, but because of antifungal treatment. Resistance compartmentalization illustrates how resistance might be overlooked if susceptibility testing is restricted to bloodstream isolates.