Candida Auris Isolates Research Articles

Isolation of Candida auris in surgical wound cultures as a probable cause for invasive spinal infection: a case report

BackgroundC. auris is identified as an emerging multi-drug resistant fungal threat causing invasive infections and hospital outbreaks. C. auris effectively colonizes the skin, leading to invasive candidiasis by entering the bloodstream and/or the deeper tissues when there is a breach of the skin barrier, such as a surgical wound. The purpose of this report is to present a case of a possible C. auris spine infection through this mechanism.Case presentationA 73-year-old male who was diagnosed with spondylodiscitis following a multiple-level kyphoplasty-vertebroplasty was admitted to our department. The patient underwent surgical debridement and posterior stabilization. The only pathogen isolated was C. auris from surgical wound cultures postoperatively. Most likely, the patient was colonized by C. auris during his stay in the Intensive Care Unit (ICU), where he was transferred after vertebroplasty-kyphoplasty. His surgical wound could serve as a portal for C. auris entry into the deeper spinal tissues following skin colonization. The patient responded to the antifungal treatment administered following the surgical debridement. In the last follow-up, he was in good clinical condition, and the inflammatory markers levels were within normal limits.ConclusionsThrough this report, we aim to highlight the critical role of C. auris skin colonization in the pathogenesis of a localized deep-seated infection and to raise awareness of the possibility of a localized invasive infection due to C. auris by contiguous spread after an ICU hospitalization in patients who have undergone recent surgery.

Antifungal Activity of Efinaconazole Compared with Fluconazole, Itraconazole, and Terbinafine Against Terbinafine- and Itraconazole-Resistant/Susceptible Clinical Isolates of Dermatophytes, Candida, and Molds.

Recently, an increasing number of resistant-to-terbinafine dermatophytosis cases have been reported. Thus, identifying an alternative antifungal agent that possesses broad-spectrum activity, including against resistant strains, is needed. We compared the antifungal activity of efinaconazole with that of fluconazole, itraconazole, and terbinafine against clinical isolates of dermatophytes, Candida, and molds using in vitro assays. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of each antifungal agent were quantified and compared. Susceptible and resistant clinical isolates of Trichophyton mentagrophytes (n = 16), Trichophyton rubrum (n = 43), Trichophyton tonsurans (n = 18), Trichophyton violaceum (n = 4), Candida albicans (n = 55), Candida auris (n = 30), Fusarium spp, Scedosporium spp, and Scopulariopsis spp (n = 15 for each) were tested. Efinaconazole was the most active antifungal agent tested against dermatophytes, with MIC50 and MIC90 (concentrations that inhibited 50% and 90% of strains tested, respectively) values of 0.002 and 0.03 µg/mL, respectively. Fluconazole, itraconazole, and terbinafine showed MIC50 and MIC90 values of 1 and 8 µg/mL, 0.03 and 0.25 µg/mL, and 0.03 and 16 µg/mL, respectively. Against Candida isolates, efinaconazole MIC50 and MIC90 values were 0.016 and 0.25 µg/mL, respectively, whereas fluconazole, itraconazole, and terbinafine had MIC50 and MIC90 values of 1 and 16 µg/mL, 0.25 and 0.5 µg/mL, and 2 and 8 µg/mL, respectively. Against various mold species, efinaconazole MIC values ranged from 0.016 to 2 µg/mL versus 0.5 to greater than 64 µg/mL for the comparators. Efinaconazole showed superior potent activity against a broad panel of susceptible and resistant dermatophyte, Candida, and mold isolates.

Two outbreaks and sporadic occurrences of Candida auris from one hospital in China: an epidemiological, genomic retrospective study.

To investigate the clinical relevance, origin, transmission, and resistance of Candida auris (C. auris) isolates from two outbreaks and sporadic occurrences from one hospital in China. A total of 135 C. auris isolates were collected. Clinical characteristics were obtained and antifungal susceptibility testing (AFST) was performed using the method of broth microdilution. Phylogenetic tree, WGS analysis, and single nucleotide polymorphisms (SNPs) were used to determine the origin, transmission, and resistance mechanisms. A total of 31 patients (91.2%, 31/34) received invasive medical procedures and 13 patients (38.2%, 13/34) had antifungal agents before C. auris infection/colonization, except one patient whose clinical information was missing. Only 4 cases of C. auris candidemia were observed. 18 patients died, 13 patients recovered, and the outcomes of 3 patients were not available. A total of 35 C. auris isolates, which were successfully cultivated and the first isolated or harbored specific drug-resistant phenotype from each patient, were selected to be sequenced and further analyzed. C. auris isolates presented low genetic variability and belonged to clade I, possibly originating from BJ004-H7 in Beijing. All 35 isolates were resistant to Fluconazole (FCZ) and amphotericin B (AMB), and 3 isolates were resistant to caspofungin (CAS). Mutations in ERG11 and FKS1 were linked to reduced azole and echinocandin susceptibility, respectively. Two outbreaks of highly clonal, multidrug-resistant C. auris isolates within the medical facility were reported. The intensive performance of disinfection measures helped block in-hospital transmission. Understanding the epidemiology, drug resistance and management of C. auris will be helpful for implementing effective infection control and treatment strategies.

Synergistic Effect of Essential Oils and Antifungal Agents in Fighting Resistant Clinical Isolates of Candida auris.

Recently, a large number of nosocomial infections have been caused by an emerging pathogen that is rising as a worldwide issue in human health: Candida auris. This yeast is considered resistant to antifungals of the first-line therapies, and consequently it is related to morbidity and mortality. Therefore, the aim of this research was to determine the in vitro anti-C. auris activity against twenty-three resistant clinical strains of different essential oils (EOs), pure or in combination with traditional antifungal agents, mainly caspofungin, fluconazole, micafungin and 5-flucytosine. Broth dilution assay was performed to evaluate the fungistatic and fungicidal effectiveness of fifteen EOs towards all the C. auris isolates. The data demonstrated that EOs were able to prevent C. auris growth, with MIC values ranging from 0.03 to 1% for the efficacious EOs (thyme, cinnamon, geranium, clove bud, lemongrass and mentha of Pancalieri), whereas the MICs were >1% for the ineffective ones. Thereafter, the six most effective EOs were used to perform the checkerboard experiments by assaying simultaneously the activity of EOs and traditional antifungals towards two selected strains. The most promising synergic combinations towards C. auris, depending on the isolate, were those with micafungin and geranium, thyme, cinnamon, lemongrass or clove bud EOs, with fluconazole and mentha of Pancalieri EO, and with 5-flucytosine and mentha of Pancalieri EO. These EOs and their combinations with antifungal drugs may provide a useful therapeutic alternative that could reduce the dose of the individual components, limiting the overall side effects. These associations might be a prospective option for the future treatment of infections, thus helping to overcome the challenging issue of resistance in C. auris.

In vitro activity of taurolidine against clinical Candida auris isolates: relevance to catheter-related bloodstream infections.

Candida auris is an evolving and concerning global threat. Of particular concern are bloodstream infections related to central venous catheters. We evaluated the activity of taurolidine, a broad-spectrum antimicrobial in catheter lock solutions, against 106 C. auris isolates. Taurolidine was highly active with a MIC50/MIC90 of 512/512 mg/L, over 20-fold lower than lock solution concentrations of ≥13,500 mg/L. Our data demonstrate a theoretical basis for taurolidine-based lock solutions for prevention of C. auris catheter-associated infections.

Candida auris: Diagnostic challenges and outbreak control in paediatric and neonatal intensive care unit in a tertiary care hospital - the first of many in Eastern India

Problem consideredAn emerging global threat, Candida auris infections have poor prognosis, high transmission rate, and potential for outbreaks. In India, prevalence of Candida auris invasive infection has been calculated to be 5.3 %. Strict surveillance and preventive measures must be implemented in intensive care units because of its propensity for rapid adaptation and potential for antifungal resistance. MethodsOutbreak investigational study was carried in paediatric and neonatal intensive care unit of a tertiary care hospital in eastern India. Clinical isolates from inpatients with candidemia were subjected to identification by microbiological tests. Deoxyribonucleic acid (DNA) sequencing done for molecular identification and determining clonal similarity of Candida auris isolates. Surveillance of intensive care units carried out to assess patient colonization, environmental contamination, and hand-carriage of yeast among healthcare workers following which strict infection control measures were implemented. ResultsBlood isolates from four candidemia patients identified microbiologically as Candida auris. Environmental surfaces found contaminated with Candida auris by surveillance included Ultrasound guided (USG) Accu-probe and Blood-pressure (BP) cuff used for all patients admitted, molecular identification of which showed homology with patient isolates. However, patients and hospital environment no longer harboured Candida auris owing to stringent Infection Prevention and Control (IPC) measures taken. ConclusionThe article emphasises multidisciplinary approach towards investigation and containment of Candida auris outbreak and how prompt surveillance and simple preventive measures could eradicate Candida auris from patients and hospital setting.

Candida auris – Comparison of sensititre YeastOne and Vitek 2 AST systems for antifungal susceptibility testing – A single centre experience

IntroductionCandida auris is emerging as an important cause of candidemia and deep seated candidal infection. We compared the susceptibility results of bloodstream Candida auris isolates by Vitek 2 with Sensititre YeastOne (SYO) method. MethodsForty-seven C. auris blood stream isolates were simultaneously tested for AFST by Vitek 2 and SYO. ResultsAll strains were resistant to Fluconazole. 25.5% isolates showed pan-azole resistance. In comparison with SYO, lower MICs for voriconazole were noted with Vitek 2 (VME rate 76.1%). All strains were sensitive to anidulafungin and micafungin by SYO. For micafungin, Vitek 2 demonstrated higher MICs and an ME rate of 23.5%. Susceptibility interpretation of caspofungin by SYO was challenged by development of ‘Eagle effect’ resulting in sensitivity of 28.2%. We studied the evolution of caspofungin ‘Eagle effect’ with SYO by serial hourly MIC readings and noted that paradoxical growth commenced at 21 hrs of incubation. Compared to SYO, Vitek 2 showed higher resistance rate to Amphotericin B with ME rate of 25.6%. ConclusionLaboratories using commercial AFST systems for Candida auris need to be aware of the possibility of ME and VME for amphotericin B and voriconazole respectively with Vitek 2 and ‘Eagle effect’ for caspofungin with SYO.

The fungicidal effectiveness of 2-Chloro-3-hydrazinylquinoxaline, a newly developed quinoxaline derivative, against Candida species.

Candida represents a prevalent fungal infection, notable for its substantial implications on morbidity and mortality rates. In the landscape of prospective treatments, quinoxaline derivatives emerge as a category of compact compounds exhibiting notable potential in addressing infections. These derivatives showcase promising antimicrobial efficacy coupled with favorable pharmacokinetic and safety characteristics. The central aim of this investigation was to examine the antifungal characteristics of 2-Chloro-3-hydrazinylquinoxaline against diverse strains of Candida and Aspergillus in vitro. Additionally, we endeavored to assess the in vivo efficacy of 2-Chloro-3-hydrazinylquinoxaline using a murine model for oral candidiasis induced by C. albicans cells ATCC 10231. 2-Chloro-3-hydrazinylquinoxaline demonstrated noteworthy effectiveness when tested against various reference strains of Candida species. It exhibited heightened efficacy, particularly against Candida krusei isolates. However, its performance against Candida albicans, Candida tropicalis, Candida glabrata, Candida parapsilosis, and Candida auris isolates exhibited variability. Notably, 2-Chloro-3-hydrazinylquinoxaline manifests variable efficacy against Aspergillus fumigatus, Aspergillus niger, Aspergillus terreus and Aspergillus flavus and no effect against Aspergillus brasiliensis. In a murine model, 2-Chloro-3-hydrazinylquinoxaline exhibited significant efficacy in combating the C. albicans cells ATCC 10231 strain, underscoring its potential as a viable treatment option. 2-Chloro-3-hydrazinylquinoxaline has demonstrated substantial potential in effectively addressing various Candida and Aspergillus species, showcasing dual attributes of antifungal and anti-inflammatory properties. However, to attain a more comprehensive understanding of its therapeutic capabilities, further investigations, incorporating additional tests and experiments, are imperative.

Anticandidal Efficacy of Green Synthesized Silver Nanoparticles Using Trans-Himalayan Plant Extracts Against Drug Resistant Clinical Isolates of Candida auris

Anticandidal Efficacy of Green Synthesized Silver Nanoparticles Using Trans-Himalayan Plant Extracts Against Drug Resistant Clinical Isolates of Candida auris

Evaluation of the first Candida auris isolates reported from Türkiye in terms of identification by various methods and susceptibility to antifungal drugs

PurposeCandida auris is increasingly being isolated from patients all over the world. It has five clades. In this study, it was aimed to compare the results of biochemical tests obtained using different methods and the antifungal susceptibility profiles of C. auris strains isolated from the first seven cases reported in Türkiye, and evaluate whether this information could be useful as preliminary data in determining the clade of strains in centers that lack the opportunity to apply molecular methods. MethodsIdentification test results obtained using API ID 32 C, API 20 C AUX, VITEK-2 YST, and MALDI-TOF MS; colony color and morphology on Chromagar Candida, CHROMagar Candida Plus media, and cornmeal-Tween 80 agar; susceptibility to antifungals were tested and compared. Antifungal susceptibility test was studied using microdilution method according to the recommendations of EUCAST. Additionally, a pilot study was conducted to investigate the value of CHROMagar Candida Plus. ResultsAll seven strains were identified as Lachancea kluyveri with API ID 32 C, Rhodotorula glutinis; Cryptococcus neoformans with API 20 C AUX, and C. auris with both VITEK-2 YST and MALDI-TOF MS. MIC values for fluconazole were very high (≥64 mg/L) for all seven strains. It was observed that 11 (37.9%) of 29 Candida parapsilosis strains formed colonies with morphology similar to C. auris on CHROMagar Candida Plus medium, leading to false positivity. ConclusionsAlthough there have been many isolations of C. auris in our country in recent years, clade distribution of only a small number of strains is known yet. In this study, when the biochemical properties and antifungal susceptibility profiles of the seven strains were evaluated, it was concluded that they exhibited some characteristics compatible with clade I. It was also observed that strains 1 and 2 may belong to a different clade.

Pore-forming peptide C14R exhibits potent antifungal activity against clinical isolates of Candida albicans and Candida auris.

Invasive candidiasis is a global public health problem as it poses a significant threat in hospital-settings. The aim of this study was to evaluate C14R, an analog derived from peptide BP100, as a potential antimicrobial peptide against the prevalent opportunistic yeast Candida albicans and the emergent multidrug-resistant yeast Candida auris. Antifungal susceptibility testing of C14R against 99C. albicans and 105C. auris clinical isolates from Colombia, was determined by broth microdilution. Fluconazole was used as a control antifungal. The synergy between C14R and fluconazole was assessed in resistant isolates. Assays against fungal biofilm and growth curves were also carried out. Morphological alterations of yeast cell surface were evaluated by scanning electron microscopy. A permeability assay verified the pore-forming ability of C14R. C. albicans and C. auris isolates had a geometric mean MIC against C14R of 4.42 µg/ml and 5.34 µg/ml, respectively. Notably, none of the isolates of any species exhibited growth at the highest evaluated peptide concentration (200 µg/ml). Synergistic effects were observed when combining the peptide and fluconazole. C14R affects biofilm and growth of C. albicans and C. auris. Cell membrane disruptions were observed in both species after treatment with the peptide. It was confirmed that C14R form pores in C. albicans' membrane. C14R has a potent antifungal activity against a large set of clinical isolates of both C. albicans and C. auris, showing its capacity to disrupt Candida membranes. This antifungal activity remains consistent across isolates regardless of their clinical source. Furthermore, the absence of correlation between MICs to C14R and resistance to fluconazole indicates the peptide's potential effectiveness against fluconazole-resistant strains. Our results suggest the potential of C14R, a pore-forming peptide, as a treatment option for fungal infections, such as invasive candidiasis, including fluconazole and amphotericin B -resistant strains.

Evaluation of the efficacy of three medical device detergents on bacteria and yeast derived biofilm: a comparative study

Background: This study aimed to evaluate the efficacy of three medical detergents against bacteria and yeast-derived biofilms. Methods: The biofilm removal efficacy of EmpowerTM (Metrex, USA), CidezymeTM (Johnson and Johnson Medical Inc, USA), and Matrix mintTM (Whiteley Medical, Australia) were compared to that of chlorine bleach. Biofilms were produced using Staphylococcus aureus RN9120, Escherichia coli ATCC35218, Pseudomonas aeruginosa ATCC27853, Candida albicans ATCC14053, and clinical isolates of Enterococcus faecalis, E. coli, Klebsiella pneumoniae, Candida auris, and Trichosporon asahii. The organisms were suspended in tryptic soy broth (TSB) in 96-well microplates and cultured for 72 hours. They were treated with the detergents, and the residual biofilm mass was quantified using crystal violet staining followed by optical density measurements at 620 nm (OD620). Results: EmpowerTM and CidezymeTM significantly reduced the biofilm mass derived from all species by > 50% of OD620 at 37ºC except those from E. faecalis, T. asahii, and C. auris. Matrix mintTM had no effect on the biofilms under any condition. Conclusion: The culture conditions and the species of the biofilm-producing organism influenced the effectiveness of the detergent. Biofilms produced by E. faecalis, C. auris, and T. asahii were resistant to all detergent treatments under all conditions.

Virulence Traits and Azole Resistance in Korean Candida auris Isolates.

We analyzed the virulence traits and azole resistance mechanisms of 104 Candida auris isolates collected from 13 Korean hospitals from 1996 to 2022. Of these 104 isolates, 96 (5 blood and 91 ear isolates) belonged to clade II, and 8 (6 blood and 2 other isolates) belonged to clade I. Fluconazole resistance (minimum inhibitory concentration ≥32 mg/L) was observed in 68.8% of clade II and 25.0% of clade I isolates. All 104 isolates were susceptible to amphotericin B and three echinocandins. In 2022, six clade I isolates indicated the first nosocomial C. auris cluster in Korea. Clade II C. auris isolates exhibited reduced thermotolerance at 42 °C, with diminished in vitro competitive growth and lower virulence in the Galleria mellonella model compared to non-clade II isolates. Of the 66 fluconazole-resistant clade II isolates, several amino acid substitutions were identified: Erg11p in 14 (21.2%), Tac1Ap in 2 (3.0%), Tac1Bp in 62 (93.9%), and Tac1Bp F214S in 33 (50.0%). Although there were a limited number of non-clade II isolates studied, our results suggest that clade II C. auris isolates from Korean hospitals might display lower virulence traits than non-clade II isolates, and their primary fluconazole resistance mechanism is linked to Tac1Bp mutations.

Whole genome sequencing analysis demonstrates therapy-induced echinocandin resistance in Candida auris isolates.

Candida auris is an emerging, multidrug-resistant yeast, causing outbreaks in healthcare facilities. Echinocandins are the antifungal drugs of choice to treat candidiasis, as they cause few side effects and resistance is rarely found. Previously, immunocompromised patients from Kuwait with C. auris colonisation or infection were treated with echinocandins, and within days to months, resistance was reported in urine isolates. To determine whether the development of echinocandin resistance was due to independent introductions of resistant strains or resulted from intra-patient resistance development, whole genome sequencing (WGS) single-nucleotide polymorphism (SNP) analysis was performed on susceptible (n = 26) and echinocandin-resistant (n = 6) isolates from seven patients. WGS SNP analysis identified three distinct clusters differing 17-127 SNPs from two patients, and the remaining isolates from five patients, respectively. Sequential isolates within patients had a maximum of 11 SNP differences over a time period of 1-10 months. The majority of isolates with reduced susceptibility displayed unique FKS1 substitutions including a novel FKS1M690V substitution, and nearly all were genetically related, ranging from only three to six SNP differences compared to susceptible isolates from the same patient. Resistant isolates from three patients shared the common FKS1S639F substitution; however, WGS analysis did not suggest a common source. These findings strongly indicate that echinocandin resistance is induced during antifungal treatment. Future studies should determine whether such echinocandin-resistant strains are capable of long-term colonisation, cause subsequent breakthrough candidiasis, have a propensity to cross-infect other patients, or remain viable for longer time periods in the hospital environment.

Does repeated exposure to hydrogen peroxide induce Candida auris resistance?

BackgroundTo minimize environmental colonization by microorganisms that may persist and thrive in healthcare settings, thus reducing healthcare-associated infections (HAIs), new insights over already known biocides are certainly of relevance. Although the efficacy of hydrogen peroxide (H2O2) against the emergent yeast Candida auris is moderately documented, concerns over the potential induction of resistance after repeated exposure do persist. The main objective of the present study was to evaluate the hypothetical induction of Candida auris resistance following 30 days of consecutive exposure to lethal and sublethal concentrations of H2O2. Furthermore, the authors aimed to elucidate about the rank of efficacy of H2O2 against C. auris comparing to other Candida species and whether different strains of C. auris may display different susceptibilities to H2O2.MethodsDuring the induction of resistance assays, both type strains and clinical isolates of Candida auris, Candida albicans and Candida parapsilosis were exposed repeatedly to defined concentrations of H2O2, for 30 days.ResultsAfter that period, no significant differences were found when comparing the minimal inhibitory concentration values of H2O2 in case of the induced strains versus each respective positive control. Moreover, H2O2 displayed similar effectiveness against all the tested Candida species and no differences were demonstrated among the distinct strains of C. auris.ConclusionsThe adoption of H2O2 solutions in routine protocols in order to promote disinfection standards against Candida auris, improving patient safety and reducing healthcare costs, is certainly welcomed.

Development of a high-resolution melt-based assay to rapidly detect the azole-resistant Candida auris isolates.

Candida auris is a multidrug-resistant yeast that rapidly spreads, making it the leading Candidate for the next pandemic. One main leading cause of emerging resistant C. auris isolates is nonsynonymous mutations. This study aimed to detect the Y132F mutation, one of the most important azole resistance-associated mutations in the ERG-11 gene of C. auris, by developing a reliable high-resolution melt (HRM)-based method. Five C. auris isolates from Iran, plus three control isolates from other Clades were used in the study. The antifungal susceptibility testing through micro broth dilution was performed to recheck their susceptibility to three azole antifungals, including fluconazole, itraconazole, and voriconazole. Moreover, the polymerase chain reaction (PCR) sequencing of the ERG-11 gene was performed. Following the bioinformatic analysis and HRM-specific primer design, an HRM-based assay was developed and evaluated to detect ERG-11 mutations. The minimum inhibitory concentrations of fluconazole among Iranian C. auris isolates ranged from 8 to 64 μg/mL. The PCR-sequencing of the ERG-11 gene and bioinformatic analyses revealed the mutation of Y132F, a substitution consequence of A to T on codon 395 in one fluconazole-resistant isolate (IFRC4050). The developed HRM assay successfully differentiated the targeted single nucleotide polymorphism between mutant and wild types (temperature [Tm]: 81.79 ℃ - cycle threshold [CT]: 20.06 for suspected isolate). For both mutant and non-mutant isolates, the mean Tm range was 81.79-82.39 °C and the mean CT value was 20.06-22.93. These results were completely in accordance with the findings of DNA sequencing. The fast-track HRM-based method successfully detected one of the most common mechanisms of resistance in the ERG-11 gene of C. auris within 3 h. Finally, the development of more panels of HRM assays for the detection of all azole resistance mutations in C. auris ERG-11 is recommended to expand the scope of the field and facilitate the elaboration of rapid and accurate methods of antifungal resistance assessment.

Efficacy of 23 commonly used liquid disinfectants against Candida auris isolates from the 4 major clades.

We tested the effectiveness of 23 disinfectants used in healthcare facilities against isolates from the 4 major clades of Candida auris. Sporicidal disinfectants were consistently effective, whereas quaternary-ammonium disinfectants had limited activity. Quaternary-ammonium-alcohol and hydrogen-peroxide-based disinfectants varied in effectiveness against C. auris.

Novel Non-Hot Spot Modification in Fks1 of Candida auris Confers Echinocandin Resistance.

We determined the echinocandin susceptibility and FKS1 genotypes of 13 clinical isolates of Candida auris that were recovered from 4 patients at a tertiary care center in Salvador, Brazil. Three isolates were categorized as echinocandin-resistant, and they harbored a novel FKS1 mutation that led to an amino acid change W691L located downstream from hot spot 1. When introduced to echinocandin-susceptible C. auris strains by CRISPR/Cas9, Fks1 W691L induced elevated MIC values to all echinocandins (anidulafungin, 16 to 32×; caspofungin, >64×; micafungin, >64×).

Novel antifungal triazoles with alkynyl-methoxyl side chains: Design, synthesis, and biological activity evaluation

Previous work led to the rational design, synthesis and testing of novel antifungal triazole analogues bearing alkynyl-methoxyl side chains. Tests of in vitro antifungal activity showed Candida albicans SC5314 and Candida glabrata 537 gave MIC values of ≤0.125 μg/mL for most of the compounds. Among these, compounds 16, 18, and 29 displayed broad-spectrum antifungal activity against seven human pathogenic fungal species, two fluconazole-resistant C. albicans isolates and two multi-drug resistant Candida auris isolates. Moreover, 0.5 μg/mL of 16, 18, and 29 was more effective than 2 μg/mL of fluconazole at inhibiting fungal growth of the strains tested. The most active compound (16) completely inhibited the growth of C. albicans SC5314 at 16 μg/mL for 24 h, affected biofilm formation and destroyed the mature biofilm at 64 μg/mL. Several Saccharomyces cerevisiae strains, overexpressing recombinant Cyp51s or drug efflux pumps, indicated 16, 18, and 29 targeted Cyp51 without being significantly affected by a common active site mutation, but were susceptible to target overexpression and efflux by both MFS and ABC transporters. GC-MS analysis demonstrated that 16, 18, and 29 interfered with the C. albicans ergosterol biosynthesis pathway by inhibition at Cyp51. Molecular docking studies elucidated the binding modes of 18 with Cyp51. The compounds showed low cytotoxicity, low hemolytic activity and favorable ADMT properties. Importantly, compound 16 showed potent in vivo antifungal efficacy in the G. mellonella infection model. Taken together, this study presents more effective, broad-spectrum, low toxicity triazole analogues that can contribute to the development of novel antifungal agents and help overcome antifungal resistance.

Discovery of novel triazoles containing benzyloxy phenyl isoxazole side chain with potent and broad-spectrum antifungal activity

As a continuation study, 29 novel triazoles containing benzyloxy phenyl isoxazole side chain were designed and synthesized based on our previous work. The majority of the compounds exhibited high potency in vitro antifungal activities against eight pathogenic fungi. The most active compounds 13, 20 and 27 displayed outstanding antifungal activity with MIC values ranging from <0.008 µg/mL to 1 µg/mL, and showed potent activity against six drug-resistant Candida auris isolates. Growth curve assays further confirmed the high potency of these compounds. Moreover, compounds 13, 20 and 27 showed a potent inhibitory activity on biofilm formation of C. albicans SC5314 and C. neoformans H99. Notably, compound 13 showed no inhibition of human CYP1A2 and low inhibitory activity against CYP2D6 and CYP3A4, suggesting a low risk of drug-drug interactions. With high potency in vitro and in vivo and good safety profiles, compound 13 will be further investigated as a promising candidate.