In Vitro and In Vivo Antifungal Activity of AmBisome Compared to Conventional Amphotericin B and Fluconazole against Candida auris

Vertebrate and invertebrate animal infection models of Candida auris pathogenicity

Candida auris is an emerging fungal pathogen with several concerning qualities. First recognized in 2009, it has arisen in multiple geographically distinct genomic clades nearly simultaneously. C. auris strains are typically multidrug resistant and colonize the skin much better than most other pathogenic fungi; it also persists on abiotic surfaces, enabling outbreaks due to transmission in health care facilities. All these suggest a biology substantially different from the 'model' fungal pathogen, Candida albicans and support intensive investigation of C. auris biology directly. To uncover novel virulence mechanisms in this species requires the development of appropriate animal infection models. Various studies using mice, the definitive model, are inconsistent due to differences in mouse and fungal strains, immunosuppressive regimes, doses, and outcome metrics. At the same time, developing models of skin colonization present a route to new insights into an aspect of fungal pathogenesis that has not been well studied in other species. We also discuss the growing use of nonmammalian model systems, including both vertebrates and invertebrates, such as zebrafish, C. elegans, Drosophila, and Galleria mellonella, that have been productively employed in virulence studies with other fungal species. This review will discuss progress in developing appropriate animal models, outline current challenges, and highlight opportunities in demystifying this curious species.

Advancements in nanoparticle-based therapies for multidrug-resistant candidiasis infections: a comprehensive review

Candida auris, a rapidly emerging multidrug-resistant fungal pathogen, poses a global health threat, with cases reported in over 47 countries. Conventional detection methods struggle, and the increasing resistance ofC. auristo antifungal agents has limited treatment options. Nanoparticle-based therapies, utilizing materials like silver, carbon, zinc oxide, titanium dioxide, polymer, and gold, show promise in effectively treating cutaneous candidiasis. This review explores recent advancements in nanoparticle-based therapies, emphasizing their potential to revolutionize antifungal therapy, particularly in combatingC. aurisinfections. The discussion delves into mechanisms of action, combinations of nanomaterials, and their application against multidrug-resistant fungal pathogens, offering exciting prospects for improved clinical outcomes and reduced mortality rates. The aim is to inspire further research, ushering in a new era in the fight against multidrug-resistant fungal infections, paving the way for more effective and targeted therapeutic interventions.

Defining Optimal Doses of Liposomal Amphotericin B Against Candida auris: Data From an In Vitro Pharmacokinetic/Pharmacodynamic Model

BACKGROUND

Candida auris isolates exhibit elevated amphotericin B (AMB) minimum inhibitory concentrations (MICs). As liposomal AMB (L-AMB) can be safely administered at high doses, we explored L-AMB pharmacodynamics against C. auris isolates in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) dilution model.

METHODS

Four C. auris isolates with Clinical and Laboratory Standards Institute (CLSI) AMB MICs = 0.5-2 mg/L were tested in an in vitro PK/PD model simulating L-AMB pharmacokinetics. The in vitro model was validated using a Candida albicans isolate tested in animals. The peak concentration (Cmax)/MIC versus log10 colony-forming units (CFU)/mL reduction from the initial inoculum was analyzed with the sigmoidal model with variable slope (Emax model). Monte Carlo analysis was performed for the standard (3 mg/kg) and higher (5 mg/kg) L-AMB doses.

RESULTS

The in vitro PK/PD relationship Cmax/MIC versus log10 CFU/mL reduction followed a sigmoidal pattern (R2 = 0.91 for C. albicans, R2 = 0.86 for C. auris). The Cmax/MIC associated with stasis was 2.1 for C. albicans and 9 for C. auris. The probability of target attainment was >95% with 3 mg/kg for wild-type C. albicans isolates with MIC ≤2 mg/L and C. auris isolates with MIC ≤1 mg/L whereas 5 mg/kg L-AMB is needed for C. auris isolates with MIC 2 mg/L.

CONCLUSIONS

L-AMB was 4-fold less active against C. auris than C. albicans. Candida auris isolates with CLSI MIC 2 mg/L would require a higher L-AMB dose.

Liposomal formulation of a new antifungal hybrid compound provides protection against Candida auris in the ex vivo skin colonization model

The newly emerged pathogen, Candida auris, presents a serious threat to public health worldwide. This multidrug-resistant yeast often colonizes and persists on the skin of patients, can easily spread from person to person, and can cause life-threatening systemic infections. New antifungal therapies are therefore urgently needed to limit and control both superficial and systemic C. auris infections. In this study, we designed a novel antifungal agent, PQA-Az-13, that contains a combination of indazole, pyrrolidine, and arylpiperazine scaffolds substituted with a trifluoromethyl moiety. PQA-Az-13 demonstrated antifungal activity against biofilms of a set of 10 different C. auris clinical isolates, representing all four geographical clades distinguished within this species. This compound showed strong activity, with MIC values between 0.67 and 1.25 µg/mL. Cellular proteomics indicated that PQA-Az-13 partially or completely inhibited numerous enzymatic proteins in C. auris biofilms, particularly those involved in both amino acid biosynthesis and metabolism processes, as well as in general energy-producing processes. Due to its hydrophobic nature and limited aqueous solubility, PQA-Az-13 was encapsulated in cationic liposomes composed of soybean phosphatidylcholine (SPC), 1,2-dioleoyloxy-3-trimethylammonium-propane chloride (DOTAP), and N-(carbonyl-methoxypolyethylene glycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine, sodium salt (DSPE-PEG 2000), and characterized by biophysical and spectral techniques. These PQA-Az-13-loaded liposomes displayed a mean size of 76.4 nm, a positive charge of +45.0 mV, a high encapsulation efficiency of 97.2%, excellent stability, and no toxicity to normal human dermal fibroblasts. PQA-Az-13 liposomes demonstrated enhanced antifungal activity levels against both C. auris in in vitro biofilms and ex vivo skin colonization models. These initial results suggest that molecules like PQA-Az-13 warrant further study and development.

Limitations of current chemotherapy and future of nanoformulation-based AmB delivery for visceral leishmaniasis-An updated review

Visceral leishmaniasis (VL) is the most lethal of all leishmaniasis diseasesand the second most common parasiticdisease after malaria and,still, categorized as a neglected tropical disease (NTD). According to the latest WHO study, >20 Leishmania species spread 0.7-1.0 million new cases of leishmaniasis each year. VL is caused by the genus, Leishmania donovani (LD), which affects between 50,000 and 90,000 people worldwide each year. Lack of new drug development, increasing drug resistance, toxicity and high cost even with the first line of treatmentof Amphotericin B (AmB), demands new formulation for treatment of VLFurther the lack of a vaccine, allowedthe researchers to develop nanofomulation-based AmB for improved delivery. The limitation of AmB is its kidney and liver toxicity which forced the development of costly liposomal AmB (AmBisome) nanoformulation. Success of AmBisome have inspired and attracted a wide range of AmB nanoformulations ranging from polymeric, solid lipid, liposomal/micellar, metallic, macrophage receptor-targetednanoparticles (NP) and even with sophisticated carbon/quantum dot-based AmBnano delivery systems. Notably, NP-based AmB delivery has shown increased efficacy due to increased uptake, on-target delivery and synergistic impact of NP and AmB. In this review, we have discussed the different forms of leishmaniasis disease and their current treatment options with limitations. The discovery, mechanism of action of AmB, clinical status of AmB and improvement with AmBisome over fungizone (AmB-deoxycholate)for VL treatment was further discussed. At last, the development of various AmB nanoformulation was discussed along with its adavantages over traditional chemotherapy-based delivery.

In Vivo Efficacy of Amphotericin B against Four Candida auris Clades

Candida auris is a multidrug-resistant fungus against which in some clinical situations amphotericin B (AMB) remains the alternative or first line drug. We compared daily 1 mg/kg of AMB efficacy in a neutropenic murine bloodstream infection model against 10 isolates representing four C. auris clades (South Asian n = 2; East Asian n = 2; South African n = 2; South American n = 4; two of which were of environmental origin). Five days of AMB treatment significantly increased the survival rates in mice infected with isolates of the East Asian clade, and 1 isolate each from the South African and South American clades (originated from bloodstream), but not in mice infected with the South Asian and 2 environmental isolates from the South American clades. AMB treatment decreased the fungal burden in mice infected with the 2 isolates each from East Asian and South African, and 1 out of 2 bloodstream isolates from South American clades in the hearts (p < 0.01), kidneys (p < 0.01) and brain (p < 0.05). AMB treatment, regardless of clades, significantly decreased colony forming units in the urine at day 3. However, histopathological examination in AMB-treated mice revealed large aggregates of yeast cells in the kidneys and hearts, and focal lesions in the cerebra and cerebelli, regardless of precise C. auris clade. Our clade-specific data confirm that the efficacy of AMB against C. auris is weak, explaining the therapeutic failures in clinical situations. Our results draw attention to the necessity to maximize the killing at the start of treatment to avoid later complications in the heart and central nervous system.

An Immunocompromised Mouse Model of Candida auris Systemic Infection

With the recent emergence of multidrug-resistant Candida auris, there is an urgent need for new antifungal compounds with novel pharmacodynamic and pharmacokinetic properties that can treat systemic fungal infections caused by this emerging yeast. Historically, testing the efficacy of treatment for disseminated candidiasis was accomplished using a diverse array of in vivo animal models, including mice which offer an advantage both in their similarities to humans and their lower cost of maintenance. However, in order to create effective in vivo models for testing new antifungal compounds designed to treat systemic infections, it is important that these models also mimic several of the relevant predisposing conditions that can lead to disseminated candidiasis. Here, we describe an immunocompromised mouse model of hematogenously disseminated C. auris infection, which may have utility to test the efficacy of candidate antifungal compounds.

Pharmaceutical liposomal delivery—specific considerations of innovation and challenges

Liposomal technology can enhance drug solubility and stability, achieving codelivery for combination therapy, and modulate the in vivo fate (e.g., site-specific distribution and controlled release), thereby improving treatment outcomes.

Efficacy of Voriconazole, Isavuconazole, Fluconazole, and Anidulafungin in the Treatment of Emerging Candida auris Using an Immunocompromised Murine Model of Disseminated Candidiasis

Antifungal activity of anidulafungin, voriconazole, isavuconazole, and fluconazole in the treatment of Candida auris was determined in vitro and in vivo. MICs for anidulafungin, voriconazole, isavuconazole, fluconazole, and amphotericin B were 0.5, 1, >64, 0.25, and 4 μg/ml, respectively. Significant in vivo efficacy was observed in the anidulafungin- and voriconazole-treated groups in survival and reduction in kidney tissue fungal burden compared to that in the untreated group (P values of <0.001 and 0.044, respectively). Our data showed that anidulafungin and voriconazole had comparable efficacies against C. auris, whereas isavuconazole did not show significant in vivo activity.