Echinocandin resistance, susceptibility testing and prophylaxis: implications for patient management

Uniqueness of Candida auris cell wall in morphogenesis, virulence, resistance, and immune evasion

Candida auris has drawn global attention due to its alarming multidrug resistance and the emergence of pan resistant strains. C. auris poses a significant risk in nosocomial candidemia especially among immunocompromised patients. C. auris showed unique virulence characteristics associated with cell wall including cell polymorphism, adaptation, endurance on inanimate surfaces, tolerance to external conditions, and immune evasion. Notably, it possesses a distinctive cell wall composition, with an outer mannan layer shielding the inner 1,3-β glucan from immune recognition, thereby enabling immune evasion and drug resistance. This review aimed to comprehend the association between unique characteristics of C. auris's cell wall and virulence, resistance mechanisms, and immune evasion. This is particularly relevant since the fungal cell wall has no human homology, providing a potential therapeutic target. Understanding the complex interactions between the cell wall and the host immune system is essential for devising effective treatment strategies, such as the use of repurposed medications, novel therapeutic agents, and immunotherapy like monoclonal antibodies. This therapeutic targeting strategy of C. auris holds promise for effective eradication of this resilient pathogen.

Susceptibility to caspofungin is regulated by temperature and is dependent on calcineurin in Candida albicans

IMPORTANCE

Echinocandins are the newest antifungal drugs and are first-line treatment option for life-threatening systemic infections. Due to lack of consensus regarding what temperature should be used when evaluating susceptibility of yeasts to echinocandins, typically either 30°C, 35°C, or 37°C is used. However, the impact of temperature on antifungal efficacy of echinocandins is unexplored. In the current study, we demonstrated that Candida albicans laboratory strain SC5314 was more susceptible to caspofungin at 37°C than at 30°C. We also found that calcineurin was required for temperature-modulated caspofungin susceptibility. Surprisingly, the altered caspofungin susceptibility was not due to differential expression of some canonical genes such as FKS, CHS, or CHT genes. The molecular mechanism of temperature-modulated caspofungin susceptibility is undetermined and deserves further investigations.

Development and validation of a colorimetric antifungal susceptibility testing method for the dimorphic fungus Talaromyces marneffei

Antifungal drug resistance is an emerging cause of treatment failure in invasive fungal infections, and antifungal susceptibility testing (AFST) may inform treatment decisions. Currently, there are no established AFST guidelines for Talaromyces marneffei (Tm) or other dimorphic fungi. We developed a colorimetric AFST method using a fluorescent redox indicator alamarBlue, which changes from blue to pink in proportion to cellular metabolic activity. We determined the optimal time for alamarBlue addition to be 24 h post-inoculation and for MIC reading to be 72 h post-inoculation. Our method allows three ways to determine minimum inhibitory concentration (MIC): visual inspection of color change, optical density, and fluorescence intensity. We validated the assay by determining the MICs for seven antifungals against 32 Tm clinical isolates and assessed the essential agreement (EA) and inter-rater reliability between our alamarBlue and the Clinical Laboratory Standard Institute (CLSI) broth microdilution methods. The MIC ranges (from low to high) were: 0.008-0.025 μg/ml for itraconazole, 0.004-0.13 μg/ml for voriconazole, 0.03-0.13 μg/ml for posaconazole, 0.06-0.5 µg/ml for flucytosine, 0.5-1 µg/ml for amphotericin B, 0.5-4 µg/ml for caspofungin, and 0.5-16 µg/ml for fluconazole. The EAs were 100% between all three MIC readouts of the alamarBlue method, and 94%-100% between the alamarBlue and CLSI methods. Our alamarBlue method had substantially higher inter-rater agreement and offers a more reliable method that can be standardized across laboratories in both high- and low-resource settings compared to the established CLSI methodology.

Recent Progress in Research on Mitochondrion-Targeted Antifungal Drugs: a Review

Fungal infections, which commonly occur in immunocompromised patients, can cause high morbidity and mortality. Antifungal agents act by disrupting the cell membrane, inhibiting nucleic acid synthesis and function, or inhibiting β-1,3-glucan synthase. Because the incidences of life-threatening fungal infections and antifungal drug resistance are continuously increasing, there is an urgent need for the development of new antifungal agents with novel mechanisms of action. Recent studies have focused on mitochondrial components as potential therapeutic drug targets, owing to their important roles in fungal viability and pathogenesis. In this review, we discuss novel antifungal drugs targeting mitochondrial components and highlight the unique fungal proteins involved in the electron transport chain, which is useful for investigating selective antifungal targets. Finally, we comprehensively summarize the efficacy and safety of lead compounds in clinical and preclinical development. Although fungus-specific proteins in the mitochondrion are involved in various processes, the majority of the antifungal agents target dysfunction of mitochondria, including mitochondrial respiration disturbance, increased intracellular ATP, reactive oxygen species generation, and others. Moreover, only a few drugs are under clinical trials, necessitating further exploration of possible targets and development of effective antifungal agents. The unique chemical structures and targets of these compounds will provide valuable hints for further exploiting new antifungals.

P4-ATPase subunit Cdc50 plays a role in yeast budding and cell wall integrity in Candida glabrata

BACKGROUND

As highly-conserved types of lipid flippases among fungi, P4-ATPases play a significant role in various cellular processes. Cdc50 acts as the regulatory subunit of flippases, forming heterodimers with Drs2 to translocate aminophospholipids. Cdc50 homologs have been reported to be implicated in protein trafficking, drug susceptibility, and virulence in Saccharomyces cerevisiae, Candida albicans and Cryptococcus neoformans. It is likely that Cdc50 has an extensive influence on fungal cellular processes. The present study aimed to determine the function of Cdc50 in Candida glabrata by constructing a Δcdc50 null mutant and its complemented strain.

RESULTS

In Candida glabrata, the loss of Cdc50 led to difficulty in yeast budding, probably caused by actin depolarization. The Δcdc50 mutant also showed hypersensitivity to azoles, caspofungin, and cell wall stressors. Further experiments indicated hyperactivation of the cell wall integrity pathway in the Δcdc50 mutant, which elevated the major cell wall contents. An increase in exposure of β-(1,3)-glucan and chitin on the cell surface was also observed through flow cytometry. Interestingly, we observed a decrease in the phagocytosis rate when the Δcdc50 mutant was co-incubated with THP-1 macrophages. The Δcdc50 mutant also exhibited weakened virulence in nematode survival tests.

CONCLUSION

The results suggested that the lipid flippase subunit Cdc50 is implicated in yeast budding and cell wall integrity in C. glabrata, and thus have a broad influence on drug susceptibility and virulence. This work highlights the importance of lipid flippase, and offers potential targets for new drug research.

Structural and mechanistic insights into fungal β-1,3-glucan synthase FKS1

The membrane-integrated synthase FKS is involved in the biosynthesis of β-1,3-glucan, the core component of the fungal cell wall1,2. FKS is the target of widely prescribed antifungal drugs, including echinocandin and ibrexafungerp3,4. Unfortunately, the mechanism of action of FKS remains enigmatic and this has hampered development of more effective medicines targeting the enzyme. Here we present the cryo-electron microscopy structures of Saccharomyces cerevisiae FKS1 and the echinocandin-resistant mutant FKS1(S643P). These structures reveal the active site of the enzyme at the membrane-cytoplasm interface and a glucan translocation path spanning the membrane bilayer. Multiple bound lipids and notable membrane distortions are observed in the FKS1 structures, suggesting active FKS1-membrane interactions. Echinocandin-resistant mutations are clustered at a region near TM5-6 and TM8 of FKS1. The structure of FKS1(S643P) reveals altered lipid arrangements in this region, suggesting a drug-resistant mechanism of the mutant enzyme. The structures, the catalytic mechanism and the molecular insights into drug-resistant mutations of FKS1 revealed in this study advance the mechanistic understanding of fungal β-1,3-glucan biosynthesis and establish a foundation for developing new antifungal drugs by targeting FKS.

Present scenarios and future prospects of herbal nanomedicine for antifungal therapy

The current COVID-19 epidemic is a sobering reminder that human susceptibility to infectious diseases remains even in our modern civilization. After all, infectious diseases are still the major reason of death globally. Healthcare authorities have often underestimated and ignored the threat posed by "microbial dangers," although they put millions of lives at risk every year. Overlooked developing diseases including fungal infections (FIs) contribute to roughly 1.7 million fatalities per year. As many as 150 million cases of severe and potentially life-threatening FIs are reported each year. In the last few years, the number of instances has steadily increased. Most of them are invasive fungal infections that require specialized treatment and hospital care. In recent years herbal antifungal compounds have been explored to acquire effective and safe therapy against fungal infections. However, potential therapeutic effects are hampered by the poor solubility, stability, and bioavailability of these important chemicals as well as the gastric degradation that occurs in the gastrointestinal tract. To get around this issue, researchers have turned to novel drug delivery systems such as nanoemulsions, ethosomes, metallic nanoparticles, liposomes, lipid nanoparticles, transferosomes, etc by improving their limits, nanocarriers can enhance the medicinal effects of herbal oils and extracts. The present review article focuses on the available antifungal agents and their characteristics, mechanism of antifungal drugs resistance, herbal oils and extract as antifungal agents, challenges in the delivery of herbal drugs, and application of nano-drug delivery systems for effective delivery of antifungal herbal compounds.

Differentiation of Candida albicans complex species isolated from invasive and non-invasive infections using HWP1 gene size polymorphism

Background and Purpose

Taxonomy of Candida is controversial and has changed due to the investigation of the novel species. Candida africana and Candida dubliniensis are new members of the C. albicans complex that are currently gaining both clinical and epidemiologic significance. This study aimed to report the prevalence of C. africana among the strains isolated from patients using hyphal wall protein 1 (HWP1) gene size polymorphism.

Materials and Methods

In total, 235 yeasts confirmed as C. albicans complex based on chromogenic media and internal transcribed spacers sequencing isolated from various clinical forms of invasive and non-invasive candidiasis mainly candidemia were re-identified using HWP1 gene polymorphisms. The HWP1-polymerase chain reaction amplicons were re-confirmed by sequencing and BLAST analysis.

Results

Based on the HWP1 gene size polymorphism, 223 strains were identified as C. albicans (94.89%) from which 7 isolates produced two DNA fragments (850 and 941 bp). The C. dubliniensis (n=4, 1.7%), C. africana (n=1, 0.42%), and mix of C. albicans and C. africana (n=7, 2.97%) were also identified.

Conclusion

It can be said that C. albicans remains the most common Candida species, while C. dubliniensis and C. africana are rarely found among the patient isolates. Due to limited information on the molecular epidemiology of this novel yeast, more studies using molecular methods are recommended.

OUP accepted manuscript

The increasing incidence and changing epidemiology of invasive fungal infections continue to present many challenges to their effective management. The repertoire of antifungal drugs available for treatment is still limited although there are new antifungals on the horizon. Successful treatment of invasive mycoses is dependent on a mix of pathogen-, host- and antifungal drug-related factors. Laboratories need to be adept at detection of fungal pathogens in clinical samples in order to effectively guide treatment by identifying isolates with acquired drug resistance. While there are international guidelines on how to conduct in vitro antifungal susceptibility testing, these are not performed as widely as for bacterial pathogens. Furthermore, fungi generally are recovered in cultures more slowly than bacteria, and often cannot be cultured in the laboratory. Therefore, non-culture-based methods, including molecular tests, to detect fungi in clinical specimens are increasingly important in patient management and are becoming more reliable as technology improves. Molecular methods can also be used for detection of target gene mutations or other mechanisms that predict antifungal drug resistance. This review addresses acquired antifungal drug resistance in the principal human fungal pathogens and describes known resistance mechanisms and what in-house and commercial tools are available for their detection. It is emphasized that this approach should be complementary to culture-based susceptibility testing, given the range of mutations, resistance mechanisms and target genes that may be present in clinical isolates, but may not be included in current molecular assays.

Expanded Access Use of Rezafungin for Salvage Therapy of Invasive Candida glabrata Infection: A Case Report

Rezafungin is a semisynthetic, long-acting echinocandin with broad-spectrum activity against many Candida species and Aspergillus species, including a subset of drug-resistant strains. It is currently in phase III trials and was found to be safe and effective for the treatment of candidemia and/or invasive Candida infections in a phase II trial. However, there are no long-term safety or efficacy data. We report on the successful ongoing compassionate use of rezafungin obtained through expanded access for over 1 year in a patient with a multidrug-resistant Candida glabrata mediastinal infection from a vascular graft infection and retained foreign material.

Candida glabrata: Pathogenicity and Resistance Mechanisms for Adaptation and Survival

Candida glabrata is a yeast of increasing medical relevance, particularly in critically ill patients. It is the second most isolated Candida species associated with invasive candidiasis (IC) behind C. albicans. The attributed higher incidence is primarily due to an increase in the acquired immunodeficiency syndrome (AIDS) population, cancer, and diabetic patients. The elderly population and the frequent use of indwelling medical devices are also predisposing factors. This work aimed to review various virulence factors that facilitate the survival of pathogenic C. glabrata in IC. The available published research articles related to the pathogenicity of C. glabrata were retrieved and reviewed from four credible databases, mainly Google Scholar, ScienceDirect, PubMed, and Scopus. The articles highlighted many virulence factors associated with pathogenicity in C. glabrata, including adherence to susceptible host surfaces, evading host defences, replicative ageing, and producing hydrolytic enzymes (e.g., phospholipases, proteases, and haemolysins). The factors facilitate infection initiation. Other virulent factors include iron regulation and genetic mutations. Accordingly, biofilm production, tolerance to high-stress environments, resistance to neutrophil killings, and development of resistance to antifungal drugs, notably to fluconazole and other azole derivatives, were reported. The review provided evident pathogenic mechanisms and antifungal resistance associated with C. glabrata in ensuring its sustenance and survival.

Emergence of resistant Candida glabrata in Germany

Background

Candida glabrata is the second leading fungal pathogen causing candidaemia and invasive candidiasis in Europe. This yeast is recognized for its rapid ability to acquire antifungal drug resistance.

Objectives

We systematically evaluated 176 C. glabrata isolates submitted to the German National Reference Center for Invasive Fungal Infections (NRZMyk) between 2015 and 2019 with regard to echinocandin and fluconazole susceptibility.

Methods

Susceptibility testing was performed using a reference protocol (EUCAST) and a range of commercial assays. Hot spot regions of the echinocandin target FKS genes were sequenced using Sanger sequencing.

Results

In total, 84 of 176 isolates were initially classified as anidulafungin-resistant based on EUCAST testing. Of those, 71 harboured mutations in the glucan synthase encoding FKS genes (13% in FKS1, 87% in FKS2). Significant differences in anidulafungin MICs were found between distinct mutation sites. 11 FKS wild-type (WT) isolates initially classified as resistant exhibited anidulafungin MICs fluctuating around the interpretation breakpoint upon re-testing with multiple assays. Two FKS WT isolates consistently showed high anidulafungin MICs and thus must be considered resistant despite the absence of target gene mutations. Over one-third of echinocandin-resistant strains displayed concomitant fluconazole resistance. Of those, isolates linked to bloodstream infection carrying a change at Ser-663 were associated with adverse clinical outcome.

Conclusions

Resistant C. glabrata strains are emerging in Germany. Phenotypic echinocandin testing can result in misclassification of susceptible strains. FKS genotyping aids in detecting these strains, however, echinocandin resistance may occur despite a wild-type FKS genotype.

Resistance to Echinocandins Complicates a Case of Candida albicans Bloodstream Infection: A Case Report

Invasive candidiasis is known to be one of the most common healthcare-associated complications and is caused by several Candida species. First-line drugs, particularly echinocandins, are effective, but there are increasing reports of resistance to these molecules, though rarely related to C. albicans. Even though the rate of echinocandins resistance remains low (<3%), sporadic cases are emerging. Here, we present a case of bloodstream infection by a pan-echinocandin-resistant Candida albicans affecting a critically ill patient, who died in an intensive care unit following therapeutic failure and multiple organ dysfunction syndrome. This case highlights the need to suspect pan-echinocandin resistance in patients with prolonged echinocandin exposure, particularly in the presence of urinary tract colonization. Our study shows the importance of sequencing to predict therapeutic failure in patients treated with echinocandins and persistent candidemia.

Comparison of In Vitro Killing Activity of Rezafungin, Anidulafungin, Caspofungin, and Micafungin against Four Candida auris Clades in RPMI-1640 in the Absence and Presence of Human Serum

Candida auris is an emerging and frequently multidrug-resistant pathogen against which the echinocandins are the preferred therapeutic option. We compared killing activities of anidulafungin, caspofungin, micafungin, and rezafungin against 13 isolates representing four C. auris clades (South Asian n = 3; East Asian n = 3; South African n = 3; South American n = 4, of which two were of environmental origin). Minimum inhibitory concentration MICs and killing kinetics in RPMI-1640 and RPMI-1640 plus 50% serum (50% serum) were determined. The four echinocandins were never fungicidal and induced large aggregates in RPMI-1640 and, less markedly, in 50% serum. Colony forming unit CFU decreases were found more consistently in 50% serum than in RPMI-1640. Isolates from the East Asian clade were killed at ≥1-≥ 4 mg/L with all echinocandins regardless of media. Anidulafungin and micafungin produced killing at peak drug serum concentration (8 mg/L) against environmental but not clinical isolates from the South American and the South African clades. Micafungin at ≥8 mg/L but not anidulafungin produced CFU decreases against the South Asian clade as well. In 50% serum, rezafungin at ≥1-≥ 8 mg/L produced killing against all four clades. The next generation echinocandin, rezafungin, showed the same or better activity at clinically attainable trough concentration regardless of media, compared with anidulafungin, caspofungin, and micafungin against all four tested C. auris clades.

Model-Optimized Fluconazole Dose Selection for Critically Ill Patients Improves Early Pharmacodynamic Target Attainment without the Need for Therapeutic Drug Monitoring

Fluconazole has been associated with higher mortality compared with the echinocandins in patients treated for invasive candida infections. Underexposure from current fluconazole dosing regimens may contribute to these worse outcomes, so alternative dosing strategies require study. The objective of this study was to evaluate fluconazole drug exposure in critically ill patients comparing a novel model-optimized dose selection method with established approaches over a standard 14-day (336-h) treatment course. Target attainment was evaluated in a representative population of 1,000 critically ill adult patients for (i) guideline dosing (800-mg loading and 400-mg maintenance dosing adjusted to renal function), (ii) guideline dosing followed by therapeutic drug monitoring (TDM)-guided dose adjustment, and (iii) model-optimized dose selection based on patient factors (without TDM). Assuming a MIC of 2 mg/liter, free fluconazole 24-h area under the curve (fAUC24) targets of ≥200 mg · h/liter and <800 mg · h/liter were used for assessment of target attainment. Guideline dosing resulted in underexposure in 21% of patients at 48 h and in 23% of patients at 336 h. The TDM-guided strategy did not influence 0- to 48-h target attainment due to inherent procedural delays but resulted in 37% of patients being underexposed at 336 h. Model-optimized dosing resulted in ≥98% of patients meeting efficacy targets throughout the treatment course, while resulting in less overexposure compared with guideline dosing (7% versus 14%) at 336 h. Model-optimized dose selection enables fluconazole dose individualization in critical illness from the outset of therapy and should enable reevaluation of the comparative effectiveness of this drug in patients with severe fungal infections.

MixInYeast: A Multicenter Study on Mixed Yeast Infections

Invasive candidiasis remains one of the most prevalent systemic mycoses, and several studies have documented the presence of mixed yeast (MY) infections. Here, we describe the epidemiology, clinical, and microbiological characteristics of MY infections causing invasive candidiasis in a multicenter prospective study. Thirty-four centers from 14 countries participated. Samples were collected in each center between April to September 2018, and they were sent to a reference center to confirm identification by sequencing methods and to perform antifungal susceptibility testing, according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST). A total of 6895 yeast cultures were identified and MY occurred in 150 cases (2.2%). Europe accounted for the highest number of centers, with an overall MY rate of 4.2% (118 out of 2840 yeast cultures). Of 122 MY cases, the most frequent combinations were Candida albicans/C. glabrata (42, 34.4%), C. albicans/C. parapsilosis (17, 14%), and C. glabrata/C. tropicalis (8, 6.5%). All Candida isolates were susceptible to amphotericin B, 6.4% were fluconazole-resistant, and two isolates (1.6%) were echinocandin-resistant. Accurate identification of the species involved in MY infections is essential to guide treatment decisions.

In vitro activity of rezafungin against common and rare Candida species and Saccharomyces cerevisiae

BACKGROUND

Rezafungin is a novel echinocandin with excellent activity against common Candida species; however, limited data are available regarding rare Candida species.

METHODS

We determined the in vitro susceptibility of 689 clinical isolates of 5 common and 19 rare Candida species, as well as Saccharomyces cerevisiae. The activity of rezafungin was compared with that of anidulafungin, caspofungin, micafungin, amphotericin B and fluconazole, using CLSI broth microdilution methodology (Fourth Edition: M27).

RESULTS

Rezafungin MIC90 values were 0.06 mg/L for Candida albicans (n=125), Candida tropicalis (n=51), Candida dubliniensis (n=22), Candida inconspicua (n=41), Candida sojae (n=10), Candida lipolytica (n=10) and Candida pulcherrima (n=10), 0.12 mg/L for Candida glabrata (n=81), Candida krusei (n=53), Candida kefyr (n=52) and Candida fabianii (n=15), 0.25 mg/L for Candida lusitaniae (n=46) and Candida auris (n=19), 0.5 mg/L for Candida metapsilosis (n=15) and S. cerevisiae (n=21), 1 mg/L for Candida orthopsilosis (n=15) and Candida guilliermondii (n=27) and 2 mg/L for Candida parapsilosis sensu stricto (n=59). Caspofungin MIC90 values were 0.25-2 mg/L for all species, while micafungin and anidulafungin MIC90 values were similar to those of rezafungin. Fluconazole resistance was found in C. albicans (5.6%) and C. glabrata (4.9%); rezafungin was effective against these isolates as well. Amphotericin B MIC values did not exceed 2 mg/L.

CONCLUSIONS

Rezafungin showed excellent in vitro activity against both WT and azole-resistant Candida species, as well as against S. cerevisiae. Rezafungin had similar activity to other echinocandins (excluding caspofungin) against common Candida species and, notably, against clinically relevant uncommon Candida species.

Review on Current Status of Echinocandins Use

Fungal infections are rising all over the world every year. There are only five medical compound classes for treatment: triazoles, echinocandins, polyenes, flucytosine and allylamine. Currently, echinocandins are the most important compounds, because of their wide activity spectrum and much lower sides effects that may occur during therapy with other drugs. Echinocandins are secondary metabolites of fungi, which can inhibit the biosynthesis of β-(1,3)-D-glucan. These compounds have fungicidal and fungistatic activity depending on different genera of fungi, against which they are used. Echinocandin resistance is rare—the major cause of resistance is mutations in the gene encoding the β-(1,3)-D-glucan synthase enzyme. In this review of the literature we have summarized the characteristics of echinocandins, the mechanism of their antifungal activity with pharmacokinetics and pharmacodynamics, and the resistance issue.

Evaluation of Resistance Development to the Gwt1 Inhibitor Manogepix (APX001A) in Candida Species

Manogepix (MGX) targets the conserved fungal Gwt1 enzyme required for acylation of inositol early in the glycosylphosphatidylinositol biosynthesis pathway. The prodrug fosmanogepix is currently in clinical development for the treatment of invasive fungal infections. We determined that the median frequencies of spontaneous mutations conferring reduced susceptibility to MGX in Candida albicans, C. glabrata, and C. parapsilosis ranged from 3 × 10-8 to <1.85 × 10-8 Serial passage on agar identified mutants of C. albicans and C. parapsilosis with reduced susceptibility to MGX; however, this methodology did not result in C. glabrata mutants with reduced susceptibility. Similarly, serial passage in broth resulted in ≤2-fold changes in population MIC values for C. tropicalis, C. auris, and C. glabrata A spontaneous V163A mutation in the Gwt1 protein of C. glabrata and a corresponding C. albicans heterozygous V162A mutant were obtained. A C. glabrata V163A Gwt1 mutant generated using CRISPR, along with V162A and V168A mutants expressed in C. albicans and Saccharomyces cerevisiae Gwt1, respectively, all demonstrated reduced susceptibility to MGX versus control strains, suggesting the importance of this valine residue to MGX binding across different species. Cross-resistance to the three major classes of antifungals was evaluated, but no changes in susceptibility to amphotericin B or caspofungin were observed in any mutant. No change was observed in fluconazole susceptibility, with the exception of a single non-Gwt1 mutant, where a 4-fold increase in the fluconazole MIC was observed. MGX demonstrated a relatively low potential for resistance development, consistent with other approved antifungal agents and those in clinical development.

A Histone Acetyltransferase Inhibitor with Antifungal Activity against CTG clade Candida Species

Candida species represent one of the most frequent causes of hospital-acquired infections in immunocompromised patient cohorts. Due to a very limited set of antifungals available and an increasing prevalence of drug resistance, the discovery of novel antifungal targets is essential. Targeting chromatin modifiers as potential antifungal targets has gained attention recently, mainly due to their role in regulating virulence in Candida species. Here, we describe a novel activity for the histone acetyltransferase inhibitor Cyclopentylidene-[4-(4-chlorophenyl)thiazol-2-yl)hydrazone (CPTH2) as a specific inhibitor of CTG clade Candida species. Furthermore, we show that CPTH2 has fungicidal activity and protects macrophages from Candida-mediated death. Thus, this work could provide a starting point for the development of novel antifungals specific to CTG clade Candida species.

Efficacy of humanized single large doses of caspofungin on the lethality and fungal tissue burden in a deeply neutropenic murine model against Candida albicans and Candida dubliniensis

Background

Echinocandins are the first-line therapy for treatment of invasive Candida infections, but the mortality rate remains high, calling for novel strategies. Giving single larger echinocandin doses infrequently is an alternative regimen. Our aim was to test this novel approach in a neutropenic murine model.

Materials and methods

We compared the in vivo efficacy of single 10 and 40 mg/kg of caspofungin (2.5× and 10× the normal humanized dose) to that of the same cumulative doses of daily 2 and 8 mg/kg doses for 5 days against 2 each of wild-type C. albicans and C. dubliniensis as well as echinocandin resistant C. albicans. As a comparator, we tested daily 1 mg/kg amphotericin B.

Results

In lethality experiments, all caspofungin and amphotericin B regimens improved survival against wild-type C. albicans and C. dubliniensis clinical isolates (P<0.0001) and decreased the mean fungal kidney burdens of both species compared to controls. However, fungal kidney burden decreases were not always statistically significant, especially with single 10 or 40 mg/kg caspofungin doses. Amphotericin B was the least active drug against wild-type C. albicans. Against echinocandin-resistant strains, monodose 40 mg/kg caspofungin and 1 mg/kg of daily amphotericin B were effective in lethality experiments. Although, significant kidney CFU decreases were never found, except for amphotericin B against one of the isolates (p<0.05 at day 3 and p<0.001 at day 6).

Conclusion

Single 40 mg/kg caspofungin and 1 mg/kg amphotericin B proved to be effective in the lethality experiments against wild-type and echinocandin-resistant C. albicans and wild-type C. dubliniensis. This was not always shown regarding fungal tissue burdens. Single caspofungin doses used in mice in this study are attainable in humans as well, suggesting a potential place of this dosing strategy not only in prevention but also in curative treatment of evolved invasive Candida infections.

Breakthrough candidemia after the introduction of broad spectrum antifungal agents: A 5-year retrospective study

Candidemia is the main invasive fungal disease among hospitalized patients. Several breakthrough candidemia (BrC) cases have been reported, but few studies evaluate the epidemiology, risk factors, molecular characterization, antifungal susceptibility profile and outcome of those patients, especially in developing countries and including patients using broad spectrum antifungals. We conducted a retrospective study from 2011 to 2016, including patients aged 12 years or older with candidemia. Epidemiological characteristics and risk factors for candidemia were evaluated and compared with patients with BrC using univariate and multivariate analysis. Sequential Candida isolates from BrC were identified by internal transcribed spacer sequencing, genotyped with amplified fragment length polymorphism fingerprinting (AFLP), and tested for antifungal susceptibility. From 148 candidemia episodes, 27 breakthrough episodes (18%) were identified, with neutropenia and mucositis being independent risk factors for BrC. Candida non-albicans was more frequent in the BrC group (P < .001). AFLP showed high correlation with conventional methods of identification among breakthrough isolates and a high genetic similarity among isolates from the same patient was observed. C. albicans was the most susceptible species with low MIC values for all antifungal agents tested. In contrast, we found isolates of C. glabrata, C. parapsilosis and C. tropicalis resistant to triazoles and echinocandins. In conclusion, BrC occurred mainly in severely immunosuppressed patients, with neutropenia and mucositis. Mortality did not differ between the groups. Candida non-albicans species were more recovered from BrC, with C. albicans being the most susceptible to antifungals.

Vaginal candidiasis among women of reproductive age in Dnipro city (Ukraine): Species spectrum of Candida and their susceptibility to antimycotics

Candidiasis is one of the most common pathological processes, especially among women of reproductive age, especially pregnant. It can be expressed as Candida carriage and as an active form of infection. Although candidiasis is caused by opportunistic microorganisms, its effects can be quite significant, so it is necessary to treat it with the use of antimycotic drugs. In view of the spread among these microorganisms of resistance to antimicrobial drugs, the determining factor for the success of therapeutic measures, it is important to make a preliminary assessment of the susceptibility to antimycotics of strains isolated from persons with Candida carriage or active candidiasis. The aim of the research was to study the species range of fungi of the genus Candida isolated from the reproductive tract in women with dysbiosis and to study their susceptibility to antimycotics. Total of 227 samples of biological material from women aged 16 to 56 years have been investigated. Microscopic and cultural methods of detecting of fungi in the primary material were used for research. For the identification of species of Candida fungi, a polymerase chain reaction method in real-time was used. It was determined that the frequency of detection of Candida fungi in the composition of vaginal microbiome during inflammatory pathological processes was 76.7%. It was shown that the incidence of Candida carriage – 51.7% – slightly exceeded the frequency of detection of the active form of infection – 48.3%. The species spectrum of pathogens included: C. albicans (57.1%), C. krusei (12.6%), C. glabrata (19.5%) and Candida spp. (16.1%). In the case of active form of infection, C. albicans was prevalent – 64 (76.2%) cases. In the case of Candida carriage, other species were prevalent – 58 (64.4%) cases. The most effective drug against all isolates was amphotericin B – more than 87% of isolates were susceptible. The least effective drug was nystatin: less than 60% of isolates were susceptible. There is a rather high level of resistance to certain antimycotic drugs among the Candida species, which requires a prior preliminary study of the susceptibility of isolated strains to antimycotics for the purpose of choosing a rational and effective treatment scheme.

Beyond tissue concentrations: antifungal penetration at the site of infection

Despite advances in antifungal therapy, invasive fungal infections remain a significant cause of morbidity and mortality worldwide. One important factor contributing to the relative ineffectiveness of existing antifungal drugs is insufficient drug exposure at the site of infection. Despite the importance of this aspect of antifungal therapy, we generally lack a full appreciation of how antifungal drugs distribute, penetrate, and interact with their target organisms in different tissue subcompartments. A better understanding of drug distribution will be critical to guide appropriate use of currently available antifungal drugs, as well as to aid development of new agents. Herein we briefly review current perspectives of antifungal drug exposure at the site of infection and describe a new technique, matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging, which has the potential to greatly expand our understanding of drug penetration.

Biofilms and beyond: expanding echinocandin utility

Echinocandins have been in use for over 15 years, starting with the first approval in 2001. Current trends, such as increasing resistance to fluconazole and shifts toward non-albicans spp. of Candida, suggest a growing role for echinocandins, as reflected by recent (2016) updates to guidelines that recommend echinocandins as first-line treatment for candidaemia. The efficacy, tolerability, and safety of echinocandins and their target site of action (1,3-β-d-glucan synthesis) have prompted research into potential new uses, such as for treatment of biofilm infections, MDR Candida auris and dermatophytes. Moreover, new mycobiome discoveries linking inflammatory bowel disease (IBD; for instance Crohn's disease) to fungi have led to preliminary but encouraging data regarding echinocandin therapy and treatment of IBD. In this article, we will review the available evidence and potential utility of echinocandins and 1,3-β-d-glucan synthesis inhibition in these areas of emerging interest.

Use of echinocandin prophylaxis in solid organ transplantation

Invasive fungal infections (IFIs) are a major threat to patients undergoing solid organ transplantation (SOT). Owing to improvements in surgical techniques, immunosuppression therapy and antifungal prophylaxis, the incidence of IFIs has been decreasing in recent years. However, IFI-associated morbidity and mortality remain significant. Invasive candidiasis (IC) and aspergillosis (IA) are the main IFIs after SOT. Risk factors for IC and IA continue to evolve, and thus strategies for their prevention should be constantly updated and targeted to both individual patient risk factors and local epidemiology. In this review, we discuss the current epidemiology and risk factors for IFIs in SOT recipients in the context of actual approaches to antifungal prophylaxis, including experience with the use of echinocandins, after SOT.

Dissection of the regulatory role for the N-terminal domain in Candida albicans protein phosphatase Z1

The novel type, fungus specific protein phosphatase Z1 of the opportunistic pathogen, Candida albicans (CaPpz1) has several important physiological roles. It consists of a conserved C-terminal catalytic domain and a variable, intrinsically disordered, N-terminal regulatory domain. To test the function of these domains we modified the structure of CaPpz1 by in vitro mutagenesis. The two main domains were separated, four potential protein binding regions were deleted, and the myristoylation site as well as the active site of the enzyme was crippled by point mutations G2A and R262L, respectively. The in vitro phosphatase activity assay of the bacterially expressed recombinant proteins indicated that the N-terminal domain was inactive, while the C-terminal domain became highly active against myosin light chain substrate. The deletion of the N-terminal 1-16 amino acids and the G2A mutation significantly decreased the specific activity of the enzyme. Complementation of the ppz1 Saccharomyces cerevisiae deletion mutant strain with the different CaPpz1 forms demonstrated that the scission of the main domains, the two point mutations and the N-terminal 1-16 deletion rendered the phosphatase incompetent in the in vivo assays of LiCl tolerance and caffeine sensitivity. Thus our results confirmed the functional role of the N-terminal domain and highlighted the significance of the very N-terminal part of the protein in the regulation of CaPpz1.

Drug susceptibility profile of Candida glabrata clinical isolates from Iran and genetic resistant mechanisms to caspofungin

BACKGROUND

Candida glabrata is a yeast that can cause hazardous fungal infections with high mortality and drug resistance.

AIMS

The aim of this study was to determine the profile of drug susceptibility in clinical isolates of C. glabrata and review the resistance mechanisms to caspofungin.

METHODS

A total of 50 C. glabrata clinical isolates from Iran were tested for in vitro susceptibilities to amphotericin B, caspofungin, fluconazole and voriconazole. To investigate the mechanism of resistance to caspofungin, hotspot areas of FKS1 and FKS2 genes were sequenced and gene expression profile was evaluated.

RESULTS

All the isolates were susceptible to amphotericin B and caspofungin. Fluconazole resistance was exhibited in four isolates. In addition, only one isolate was resistant to voriconazole. FKS2 with 12 point mutations showed more mutations compared to FKS1 that had only two mutations. All substitutions were synonymous. FKS genes were expressed at comparable levels (no statistical significance) in caspofungin-treated and non-treated cultures.

CONCLUSIONS

The silent mutations in the hotspot areas of FKS genes and inconsiderable changes in gene expression were not associated with increased MIC (0.25μg/ml). Other mechanisms of resistance which include mutations outside the hotspot area of FKS genes could be involved in a slight increase of MIC, and they should be identified through complete FKS gene sequencing.

MSH2 Gene Point Mutations Are Not Antifungal Resistance Markers in Candida glabrata

The high rates of antifungal resistance in Candida glabrata may be facilitated by the presence of alterations in the MSH2 gene. We aimed to study the sequence of the MSH2 gene in 124 invasive C. glabrata isolates causing incident episodes of candidemia (n = 81), subsequent candidemia episodes (n = 9), endocarditis (n = 2), and in vitro-generated echinocandin-resistant isolates (n = 32) and assessed its relationship with genotypes, acquisition of antifungal resistance in vivo and in vitro, and patient prognosis. The MSH2 gene was sequenced, and isolates were genotyped using six microsatellite markers and multilocus sequence typing (MLST) based on six housekeeping genes. According to EUCAST, isolates causing candidemia (n = 90) were echinocandin susceptible, and four of them were fluconazole resistant (MIC ≥64 mg/liter). One isolate obtained from a heart valve was resistant to micafungin and anidulafungin (MICs, 2 mg/liter and 1 mg/liter, respectively). MSH2 gene mutations were present in 44.4% of the incident isolates, the most common being V239L. The presence of MSH2 mutations was not correlated with in vitro or in vivo antifungal resistance. Microsatellite and MLST revealed 27 genotypes and 17 sequence types, respectively. Fluconazole-resistant isolates were unrelated. Most MSH2 mutations were found in cluster isolates; conversely, some mutations were found in more than one genotype. No clinical differences, including previous antifungal use, were found between patients infected by wild-type MSH2 gene isolates and isolates with any point mutation. The presence of MSH2 gene mutations in C. glabrata isolates causing candidemia is not correlated with specific genotypes, the promotion of antifungal resistance, or the clinical outcome.

Comparison of Killing Activity of Micafungin Against Six Candida Species Isolated from Peritoneal and Pleural Cavities in RPMI-1640, 10 and 30% Serum

Currently echinocandins are recommended in Candida peritonitis and pleuritis. We determined micafungin killing rates (k values) at therapeutic concentrations (0.25-2 mg/L) in RPMI-1640 with and without 10 and 30% serum mimicking in vivo conditions against six Candida species isolated from peritoneal and pleural fluid. In RPMI-1640, micafungin was fungicidal against C. glabrata, C. krusei and C. kefyr within 2.27 ± 10.68, 2.69 ± 10.29 and 3.10 ± 4.41 h, respectively, while was fungistatic against C. albicans, C. tropicalis and C. parapsilosis. In 10% serum, ≥ 0.25, ≥ 0.5, ≥ 0.5 and ≥ 1 mg/L micafungin produced positive k values (killing) for all C. albicans, C. glabrata, C. kefyr and C. krusei, respectively. In 30% serum, 2 mg/L micafungin produced killing against all C. albicans, C. glabrata and C. kefyr isolates, but was ineffective against C. krusei, C. parapsilosis and 2 of 3 C. tropicalis. Micafungin exposure should be increased against non-albicans species to eradicate fungi from peritoneal and pleural cavities.

Phenotypic and genotypic variations in Candida albicans isolates from Romanian patients

Background: During the last two decades a major increase in the proportion of severe fungal infections has been noted due to the excessive use of broad-spectrum antibiotics, catheters, and a growing number of immunocompromised patients.

Objectives: This is the first investigation providing complete data regarding the phenotypic and genotypic profiles of Candida albicans (C. albicans) isolates in Romanian patients.

Methods: We investigated 301 isolates in terms of genotype determination (G), resistogram (R), phospholipase activity (Pl), haemolysis (Hl), proteinase activity (Pt), and biofilm formation (BF).

Results: The analyzed isolates of C. albicans showed low values for Pt (61.73%), Hl (95.49%), and BF (60.71%), and did not present any Pl activity (92.23%). More than half of the investigated samples were genotype A with 450 bp (52.92%) and the majority (86.19%) were resistant to sodium selenite (A), boric acid (B), sodium periodate (D) and silver nitrate (E), but sensitive to cetrimide (-). One-way ANOVA analysis revealed significant effects of the infection site on biofilm formation (p = 0.0137) and no significant correlation was found between the genotype (A, B, C) and the infection site (p =0.449).

Conclusions: Based on the obtained results it can be concluded that C. albicans isolates in Romanian patients exhibit different genotypic and phenotypic patterns, and no significant correlations between genotype and infection site could be observed.

Role of FKS Gene in the Susceptibility of Pathogenic Fungi to Echinocandins

Echinocandins are antifungal agents that specifically inhibit the biosynthesis of 1,3-β-D-glucan, a major structural component of fungal cell walls. Echinocandins are recommended as first-line or alternative/salvage therapy for candidiasis and aspergillosis in antifungal guidelines of various countries. Resistance to echinocandins has been reported in recent years. The mechanism of echinocandin resistance involves amino acid substitutions in hot spot regions of the FKS gene product, the catalytic subunit of 1,3-β-D-glucan synthase. This resistance mechanism contributes to not only acquired resistance in Candida spp., but also inherent resistance in some pathogenic fungi. An understanding of the echinocandin resistance mechanism is important to develop both effective diagnosis and treatment options for echinocandin-resistant fungal diseases.

Poor in vivo efficacy of caspofungin, micafungin and amphotericin B against wild-type Candida krusei clinical isolates does not correlate with in vitro susceptibility results

We determined micafungin, caspofungin and amphotericin B (AMB) minimum inhibitory concentration (MICs) and killing rates in RPMI-1640 and in RPMI-1640 with 50% serum against three Candida krusei bloodstream isolates. MIC ranges in RPMI-1640 were 0.125-0.25, 0.25 and 0.125-0.5 mg/L, in RPMI-1640 with 50% serum, MICs were 64-128-, 8- and 4-16-fold higher, respectively. In RPMI-1640 micafungin and caspofungin at 1, 4, 16 and 32 mg/L as well as AMB at 2 mg/L were fungicidal against all isolates in ≤3.96, ≤4.42 and 14.96 h, respectively. In RPMI-1640 with 50% serum, caspofungin was fungicidal for all isolates only at 32 mg/L, micafungin and AMB were fungistatic. In neutropenic mice, 5 mg/kg caspofungin and 1 mg/kg AMB were ineffective against two of the three isolates. Thus, in vivo efficacy of echinocandins and AMB is weak or absent against C. krusei. Prescribers treating C. krusei infections with echinocandins should watch out for clinical resistance and therapeutic failure.

Overcoming the Resistance Hurdle: Pharmacokinetic-Pharmacodynamic Target Attainment Analyses for Rezafungin (CD101) against Candida albicans and Candida glabrata

Rezafungin (CD101) is a novel echinocandin antifungal agent with activity against Aspergillus and Candida species, including azole- and echinocandin-resistant isolates. The objective of these analyses was to conduct pharmacokinetic (PK)-pharmacodynamic (PD) target attainment analyses to evaluate single and once-weekly rezafungin dosing to provide dose selection support for future clinical studies. Using a previously developed rezafungin population PK model, Monte Carlo simulations were conducted utilizing the following three intravenous rezafungin regimens: (i) a single 400 mg dose, (ii) 400 mg for week 1 followed by 200 mg weekly for 5 weeks, and (iii) 400 mg weekly for 6 weeks. Percent probabilities of achieving the nonclinical PK-PD targets associated with net fungal stasis and 1-log10 CFU reductions from baseline for Candida albicans and Candida glabrata were calculated for each rezafungin regimen. At the MIC90 for C. albicans and C. glabrata, a single 400 mg dose of rezafungin achieved probabilities of PK-PD target attainment of ≥90% through week 3 of therapy for all PK-PD targets evaluated. When evaluating the multiple-dose (i.e., weekly) regimens under these conditions, percent probabilities of PK-PD target attainment of 100% were achieved through week 6. Moreover, high (>90%) probabilities of PK-PD target attainment were achieved through week 6 following administration of the weekly regimens at or above the MIC100 values for C. albicans and C. glabrata based on contemporary in vitro surveillance data. These analyses support the use of single and once-weekly rezafungin regimens for the treatment of patients with candidemia and/or candidiasis due to C. albicans or C. glabrata.

Echinocandins for management of invasive candidiasis in patients with liver disease and liver transplantation

Candida species remains one of the most important causes of opportunistic infections worldwide. Invasive candidiasis (IC) is associated with considerable morbidity and mortality in liver disease (LD) patients if not treated promptly. Echinocandins are often recommended as a first-line empirical treatment for managing IC and can especially play a critical role in managing IC in LD patients. However, advanced LD patients are often immunocompromised and critically ill. Hence altered pharmacokinetics, drug interactions as well as tolerance issues of antifungal treatments are a concern in these patients. This comprehensive review examines the epidemiology, risk factors and diagnosis of IC in patients with LD and evaluates differences between three available echinocandins for treating this group of patients.

Susceptibility of Candida glabrata biofilms to echinocandins: alterations in the matrix composition

Candidiases are the most recurrent fungal infections, especially among immunosuppressed patients. Although Candida albicans is still the most widespread isolated species, non-Candida albicans Candida species have been increasing. The goal of this work was to determine the susceptibility of C. glabrata biofilms to echinocandins and to evaluate their effect on the biofilm matrix composition, comparing the results with other Candida species. Drug susceptibilities were assessed through the determination of minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC) and minimum biofilm eradication concentration (MBEC) of caspofungin (Csf) and micafugin (Mcf). The β-1,3 glucans content of the matrices was assessed after contact with the drugs. The data suggest that, generally, after contact with echinocandins, the concentration of β-1,3 glucans increased. These adjustments in the matrix composition of C. glabrata biofilms and the chemical differences between Csf and Mcf, seem responsible and may determine the effectivity of the drug responses.

Evaluation of candidemia and antifungal consumption in a large tertiary care Italian hospital over a 12-year period

PURPOSE

An early adequate antifungal therapy based on the knowledge of local epidemiology can reduce the candidemia-attributable mortality and the length of hospitalization. We performed a retrospective study to analyze the epidemiology of candidemia and the antifungal consumption in our hospital.

METHODS

We analyzed Candida spp. isolated from the blood, and their susceptibility profile from 2005 to 2016 in Careggi University Hospital, Florence, Italy. We also performed a stratified analysis by clinical setting where Candida spp. were isolated (Medical Wards, Surgery, Intensive Care Unit-ICU). Then, we retrospectively reviewed the annual consumption of antifungal agents and calculated the defined daily dosing for 10,000 hospital days.

RESULTS

The rate of candidemia was higher in ICU than other settings and Candida albicans was the first cause of candidemia (61.2%). After adjustment for hospital days, the rate of C. albicans showed a statistically significant parabolic trend (p < 0.001), with a peak of incidence in 2010. After 2010, we observed a reduction of candidemia due to both C. albicans and non-albicans species. Between 2005 and 2015, we reported an increasing increased use of echinocandins. As far as resistance profile is concerned, only one Candida glabrata isolate was resistant to caspofungin (1.9%) and 30% of C. glabrata were resistant to fluconazole.

CONCLUSIONS

Our data describe C. albicans as the first cause of candidemia in all the studied settings and the low rate of echinocandin resistance, despite their increased use over the study period. ICU was confirmed as the setting with the highest incidence of candidemia.

In vitro activity of the novel echinocandin CD101 at pH 7 and 4 against Candida spp. isolates from patients with vulvovaginal candidiasis

Background: The novel echinocandin CD101 has stability properties amenable to topical formulation for use in the treatment of acute vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC). CD101 has demonstrated potent antifungal activity at pH 7, but assessment of its activity at the physiological pH of the vaginal environment is needed.

Objectives: To evaluate the antifungal activity of CD101 against clinical VVC isolates of Candida spp., including azole-resistant strains, at pH 4.

Methods: MIC values of CD101 and comparators (fluconazole, itraconazole, micafungin, caspofungin and anidulafungin) were assessed via broth microdilution. MIC assays were conducted at pH 7 and 4 after 24 and 48 h against a 108 VVC isolate panel of Candida spp., including Candida albicans (n = 60), Candida glabrata (n = 21), Candida parapsilosis (n = 14) and Candida tropicalis (n = 13).

Results: Overall, MIC values of all drugs were slightly higher at pH 4 versus 7 and at 48 versus 24 h of incubation. CD101 MIC values typically exhibited ∼4-fold shifts at pH 4 and were not affected by azole susceptibility. C. parapsilosis susceptibility was the least affected at pH 4 and did not increase for most drugs.

Conclusions: CD101 had potent activity against all Candida isolates tested, including azole-resistant strains. Although there was some reduction in activity at pH 4 versus 7, the resulting MIC values were still well below the intravaginal CD101 drug concentrations anticipated to be present following topical administration. These results support continued development of topical CD101 for the treatment of VVC/RVVC.

Choosing Optimal Antifungal Agents To Prevent Fungal Infections in Nonneutropenic Critically Ill Patients: Trial Sequential Analysis, Network Meta-analysis, and Pharmacoeconomic Analysis

The use of antifungal interventions in critically ill patients prior to invasive fungal infection (IFI) being microbiologically confirmed and the preferred drug are still controversial. A systematic literature search was performed to identify randomized controlled trials (RCTs) that compared untargeted antifungal treatments applied to nonneutropenic critically ill patients. The primary outcomes were all-cause mortality and proven IFI rates. A random-effects model was used with trial sequential analyses (TSA), a network meta-analysis (NMA) was conducted to obtain indirect evidence, and a cost-effectiveness analysis using a decision-analytic model was completed from the patient perspective over a lifetime horizon. In total, 19 RCTs involving 2,556 patients (7 interventions) were included. Untargeted antifungal treatment did not significantly decrease the incidence of all-cause mortality (odds ratio [OR] = 0.89, 95% confidence interval [95%CI] = 0.70 to 1.14), but it did reduce the incidence of proven IFI (OR = 0.45, 95%CI = 0.29 to 0.71) relative to placebo/no intervention. The TSA showed that there was sufficient evidence supporting these findings. In the NMA, the only significant difference found for both primary outcomes was between fluconazole and placebo/no intervention in preventing proven IFI (OR = 0.35, 95%CI = 0.19 to 0.65). Based on drug and hospital costs in China, the incremental cost-effectiveness ratios per life-year saved for fluconazole, caspofungin, and micafungin relative to placebo/no intervention corresponded to US$889, US$9,994, and US$10,351, respectively. Untargeted antifungal treatment significantly reduced proven IFI rates in nonneutropenic critically ill patients but with no mortality benefits relative to placebo/no intervention. Among the well-tolerated antifungals, fluconazole remains the only one that is effective for IFI prevention and significantly cheaper than echinocandins.

Healthcare workers' hands as a vehicle for the transmission of virulent strains of Candida spp.: A virulence factor approach

BACKGROUND

Although the majority of Candida infections are thought to come from endogenous sources, the healthcare workers' (HCWs) hands are being increasingly reported as vehicles for the transmission of pathogens. The aim of the present study was to evaluate the susceptibility of yeast isolated from the HCWs' hands and ICU (Intensive Care Unit) surfaces to antifungal agents and to determine the virulence potential and the genetic similarity between the same.

METHODS

The susceptibility of yeasts from the HCWs' hands (n = 57) and ICU surfaces (n = 98) to conventional antifungals (fluconazole, voriconazole, amphotericin B and micafungin) was evaluated using the broth microdilution assay accordance with CLSI M27-A3. Additionally, some virulence factors such as adhesion and biofilm capacity on abiotic surfaces and on endothelial cells were evaluated, as well as germ tube formation. The similarity among yeast isolates were evaluated by the RAPD technique using the P4, OPA18 and OPE18 primers.

RESULTS

Five species of Candida were found on the HCWs' hands (C. albicans, C. parapsilosis (sensu stricto), C. glabrata, C. tropicalis and C. krusei) and two on ICU surfaces (C. albicans and C. parapsilosis (sensu stricto)). The isolates from hands had higher resistance rates, with C. glabrata having the highest indices (100% FLU; 100% MFG). The similarity of C. albicans from HCWs and ICU surfaces was ≥80% according to the three primers analyzed. Candida spp. from hands had a greater potential for adhesion and biofilm formation on abiotic surfaces (p < 0.05). C. albicans from ICU surfaces had the greatest potential of adhesion on endothelial cells after 2 and 24 h, and presented high filamentation in SEM images and formed more and larger germ tubes (p < 0.05).

CONCLUSION

the present study showed the significant virulence potential of yeasts transmitted in the hospital environment for the first time. Additionally, healthy people working in the ICU can carry these yeasts, which are capable of surviving in hospital surfaces, on their hands, offering a risk to patients, especially those who are immunocompromised.

Development of antifungal therapies using nanomaterials

The number and diversity of chemical structures currently available as antibacterial drugs is much higher compared with the number of active substances in relation to pathogenic fungi. In this review we focus on nanotechnology approaches, which offer promising strategies to create nanoagents that possess broad-spectrum antifungal activity and might overcome mechanisms of antibiotic resistance. Special attention was given to magnetic nanoparticles and their ability to restrict fungal growth directly, which depends on surface chemistry and pathogen strains. We speculate that future developments of new antifungal methods will take advantage of the current knowledge of using of magnetic nanomaterials as anticancer agents based on their ability to induce hyperthermia and enhance photosensitizing processes.

Relationship between the Antifungal Susceptibility Profile and the Production of Virulence-Related Hydrolytic Enzymes in Brazilian Clinical Strains of Candida glabrata

Candida glabrata is a facultative intracellular opportunistic fungal pathogen in human infections. Several virulence-associated attributes are involved in its pathogenesis, host-pathogen interactions, modulation of host immune defenses, and regulation of antifungal drug resistance. This study evaluated the in vitro antifungal susceptibility profile to five antifungal agents, the production of seven hydrolytic enzymes related to virulence, and the relationship between these phenotypes in 91 clinical strains of C. glabrata. All C. glabrata strains were susceptible to flucytosine. However, some of these strains showed resistance to amphotericin B (9.9%), fluconazole (15.4%), itraconazole (5.5%), or micafungin (15.4%). Overall, C. glabrata strains were good producers of catalase, aspartic protease, esterase, phytase, and hemolysin. However, caseinase and phospholipase in vitro activities were not detected. Statistically significant correlations were identified between micafungin minimum inhibitory concentration (MIC) and esterase production, between fluconazole and micafungin MIC and hemolytic activity, and between amphotericin B MIC and phytase production. These results contribute to clarify some of the C. glabrata mechanisms of pathogenicity. Moreover, the association between some virulence attributes and the regulation of antifungal resistance encourage the development of new therapeutic strategies involving virulence mechanisms as potential targets for effective antifungal drug development for the treatment of C. glabrata infections.

Killing Activity of Micafungin Against Candida albicans, C. dubliniensis and Candida africana in the Presence of Human Serum

We compared killing activity of micafungin in time-kill experiments in RPMI-1640 with and without 50% serum against Candida albicans, Candida dubliniensis and Candida africana reference strains and clinical isolates. Killing rates (k values) were determined for each strain and concentration. In RPMI-1640 MIC ranges were 0.015-0.03, 0.015-0.03 and 0.015 mg/L against C. albicans, C. dubliniensis and C. africana, respectively. In 50% serum MIC values for the three species increased 16- to 64-fold. In RPMI-1640 micafungin was fungicidal against two of three C. albicans isolates at 16 and 32 mg/L within 14.54 h and fungistatic against all C. africana and C. dubliniensis. Fifty per cent serum significantly decreased the growth rate of C. africana, but not of the other two species; weak in vivo replication ability of C. africana was confirmed in murine model. In 50% serum micafungin at 0.25 and 1 mg/L did not inhibit any of the three species (k values were always negative). Micafungin killing rate in 50% serum at 4, 16 and 32 mg/L was significantly decreased for C. albicans, but increased for C. dubliniensis compared to RPMI-1640. Killing activity of micafungin against C. africana was comparable or higher in 50% serum than in RPMI-1640. Although micafungin is a highly protein-bound drug, it was equally effective against the species of the C. albicans complex in 50% serum at therapeutic trough concentration (4 mg/L). Both in vitro and in vivo data confirmed the low virulence of C. africana compared to the two sibling species.

Decreased Killing Activity of Micafungin Against Candida guilliermondii, Candida lusitaniae, and Candida kefyr in the Presence of Human Serum

Currently, echinocandins are first-line drugs for treatment of invasive candidiasis. However, data on how serum influences killing activity of echinocandins against uncommon Candida species are limited. Therefore, the killing activity of micafungin in RPMI-1640 and in 50% serum was compared against Candida guilliermondii, Candida lusitaniae, and Candida kefyr. Minimum inhibitory concentration (MIC) ranges in RPMI-1640 were 0.5-1, 0.12-0.25, and 0.06-0.12 mg/L, respectively. In 50% serum, MICs increased 32- to 256-fold. In RPMI-1640 ≥ 0.25, ≥4, and 32 mg/L micafungin was fungicidal against all four C. kefyr (≤4.04 hours), two of three C. lusitaniae (≤16.10 hours), and two of three C. guilliermondii (≤12.30 hours), respectively. In 50% serum, all three species grew at ≤4 mg/L. Micafungin at 16-32 mg/L was fungicidal against all C. kefyr isolates (≤3.03 hours) and at 32 mg/L was fungistatic against one of three C. lusitaniae isolates. Two C. lusitaniae isolates and all three C. guilliermondii grew at all tested concentrations. Adding human serum to susceptibility test media drew attention to loss of fungicidal or fungistatic activity of micafungin in the presence of serum proteins, which is not predicted by MICs in case of C. kefyr and C. lusitaniae in RPMI-1640. Our results strongly suggest that micafungin and probably other echinocandins should be used with caution against rare Candida species.

Proper Sterol Distribution Is Required for Candida albicans Hyphal Formation and Virulence

Candida albicans is an opportunistic fungus responsible for the majority of systemic fungal infections. Multiple factors contribute to C. albicans pathogenicity. C. albicans strains lacking CaArv1 are avirulent. Arv1 has a conserved Arv1 homology domain (AHD) that has a zinc-binding domain containing two cysteine clusters. Here, we explored the role of the CaAHD and zinc-binding motif in CaArv1-dependent virulence. Overall, we found that the CaAHD was necessary but not sufficient for cells to be virulent, whereas the zinc-binding domain was essential, as Caarv1/Caarv1 cells expressing the full-length zinc-binding domain mutants, Caarv1^C3S and Caarv1^C28S, were avirulent. Phenotypically, we found a direct correlation between the avirulence of Caarv1/Caarv1, Caarrv1^AHD, Caarv1^C3S, and Caarv1^C28S cells and defects in bud site selection, septa formation and localization, and hyphal formation and elongation. Importantly, all avirulent mutant strains lacked the ability to maintain proper sterol distribution. Overall, our results have established the importance of the AHD and zinc-binding domain in fungal invasion, and have correlated an avirulent phenotype with the inability to maintain proper sterol distribution.