Echinocandin persistence directly impacts the evolution of resistance and survival of the pathogenic fungus Candida glabrata.

Recent epidemiological studies documented an alarming increase in the prevalence of echinocandin-resistant (ECR) Candida glabrata blood isolates. ECR isolates are known to arise from a minor subpopulation of a clonal population, termed echinocandin persisters. Although it is believed that isolates with a higher echinocandin persistence (ECP) are more likely to develop ECR, the implication of ECP needs to be better understood. Moreover, replacing laborious and time-consuming traditional approaches to determine ECP levels with rapid, convenient, and reliable tools is imperative to advance our understanding of this emerging concept in clinical practice. Herein, using extensive ex vivo and in vivo systemic infection models, we showed that high ECP isolates are less effectively cleared by micafungin treatment and exclusively give rise to ECR colonies. Additionally, we developed a flow cytometry-based tool that takes advantage of a SYTOX-based assay for the stratification of ECP levels. Once challenged with various collections of echinocandin-susceptible blood isolates, our assay reliably differentiated ECP levels in vitro and predicted ECP levels in real time under ex vivo and in vivo conditions when compared to traditional methods relying on colony-forming unit counting. Given the high and low ECP predictive values of 92.3% and 82.3%, respectively, our assay showed a high agreement with traditional approach. Collectively, our study supports the concept of ECP level determination in clinical settings and provides a robust tool scalable for high-throughput settings. Application of this tool facilitates the interrogation of mutant and drug libraries to further our understanding of persister biology and designing anti-persister therapeutics. IMPORTANCE: Candida glabrata is a prevalent fungal pathogen able to replicate inside macrophages and rapidly develop resistance against frontline antifungal echinocandins. Multiple studies have shown that echinocandin resistance is fueled by the survival of a small subpopulation of susceptible cells surviving lethal concentrations of echinocandins. Importantly, bacterial pathogens that exhibit high antibiotic persistence also impose a high burden and generate more antibiotic-resistant colonies. Nonetheless, the implications of echinocandin persistence (ECP) among the clinical isolates of C. glabrata have not been defined. Additionally, ECP level determination relies on a laborious and time-consuming method, which is prone to high variation. By exploiting in vivo systemic infection and ex vivo models, we showed that C. glabrata isolates with a higher ECP are associated with a higher burden and more likely develop echinocandin resistance upon micafungin treatment. Additionally, we developed an assay that reliably determines ECP levels in real time. Therefore, our study identified C. glabrata isolates displaying high ECP levels as important entities and provided a reliable and convenient tool for measuring echinocandin persistence, which is extendable to other fungal and bacterial pathogens.

A new PK/PD target for assessing efficacy of micafungin against Candida parapsilosis.

BACKGROUND: Pharmacokinetic/pharmacodynamic (PK/PD) targets of echinocandins failed to support current clinical breakpoints of Candida parapsilosis as the PTA is low for susceptible isolates despite the good clinical efficacy of echinocandins against these infections. We therefore investigated the effect of micafungin against C. parapsilosis using an in vitro PK/PD in the presence of 10% human serum. METHODS: Three susceptible (MIC = 0.5-2 mg/L) and one resistant (MIC > 8 mg/L) C. parapsilosis sensu stricto isolates were tested at two different inocula (104 and 103 cfu/mL) simulating micafungin human exposures in RPMI and in RPMI + 10% pooled human serum. The exposure-effect relationship tAUC0-24/MIC was described and different PK/PD targets were determined in order to calculate the PTA for the standard 100 mg IV q24h dose. RESULTS: A maximal effect was found at fCmax ≥ 4 mg/L in RPMI and tCmax ≥ 64 mg/L (fCmax = 0.08 mg/L) in the presence of serum for which in vitro PK/PD targets were 50 times lower. Stasis in the presence of serum was found at 272-240 tAUC0-24/MIC, close to the clinical PK/PD target (285 tAUC/MIC), validating the in vitro model. However, the PTA was low for susceptible isolates with EUCAST/CLSI MICs ≤ 2 mg/L. Among the different PK/PD targets investigated, the PK/PD target 28 tAUC/MIC associated with 10% of maximal effect with the low inoculum resulted in PTAs ≥ 95% for susceptible isolates with EUCAST/CLSI MICs ≤ 2 mg/L. CONCLUSIONS: A new PK/PD target was found for micafungin and C. parapsilosis that supports the current clinical breakpoint. This target could be used for assessing echinocandin efficacy against C. parapsilosis.

Effects of resveratrol on macrophages after phagocytosis of Candida glabrata.

Candida glabrata is believed to be the underlying cause of many human ailments, including oral, gastrointestinal, and vaginal disorders. C. glabrata-caused deep-seated infections, coupled with its resistance to antifungal drugs, may contribute to a high mortality rate. Resveratrol is a polyphenol and can achieve better therapeutic effects when administered in combination with micafungin, but the underlying molecular mechanisms remain unknown. Here, we investigate the effects of varying doses of resveratrol on the proliferation, apoptosis, and activity of macrophages, which were co-cultured with micafungin-pretreated C. glabrata. Resveratrol can restore the decreased proliferative activity of macrophages caused by the phagocytosis of C. glabrata. Further investigations demonstrated that this restoration ability exhibited a dose-dependent manner, reaching the highest level at 200 µM of resveratrol. Resveratrol tended to be more effective in inhibiting macrophage apoptosis and reducing reactive oxygen species (ROS) levels with concentration increases. In addition, at medium concentrations, resveratrol may down-regulate the expression of most inflammatory cytokines, whereas at high concentrations, it started to exert pro-inflammatory functions by up-regulating their expressions. Macrophages may shift from an anti-inflammatory (M2) phenotype to an inflammatory (M1) phenotype by resveratrol at 200 µM, and from M1 to M2 at 400 µM. Our research shows that resveratrol with micafungin are effective in treating C. glabrata infections. The resveratrol-micafungin combination can reduce the production of ROS, and promote the proliferation, inhibit the apoptosis, and activate the polarization of macrophages in a dose-dependent manner. This study offers insights into how this combination works and may provide possible direction for further clinical application of the combination.

Comparing the virulence of four major clades of Candida auris strains using a silkworm infection model: Clade IV isolates had higher virulence than the other clades.

Candida auris is an emerging fungal pathogen that is feared to spread of infection because of its propensity for multidrug resistance and high mortality rate. This pathogenic yeast is classified into four major clades by phylogenetic analyses, which are referred to the South Asia clade (clade I), East Asia clade (clade II), South Africa clade (clade III), and South America clade (clade IV), based on the location of the initial isolate. In this study, we evaluated the virulence of C. auris strains belonging to four major clades and the therapeutic effects of micafungin in a silkworm infection model. The highest mortality rate at 21 h after C. auris inoculation was observed for strains from clade IV (80% or more). In contrast, it was 20% or less in those from other clades. Antifungal susceptibility tests indicated resistance to fluconazole and sensitivity to echinocandins in the blood-derived strains. Micafungin prolonged the survival of blood-derived C. auris infected silkworms. These results suggest that the silkworm infection model is useful for evaluating the virulence of C. auris and determining its therapeutic effects.

Candida auris is an emerging fungal pathogen that has spread worldwide because of its multidrug resistance. We developed a silkworm infection model with C. auris to evaluate the virulence of clinical isolates. An evaluation system using silkworms is useful for determining C. auris virulence.

Micafungin: A promising inhibitor of UBE2M in cancer cell growth suppression.

Neddylation is a protein modification process similar to ubiquitination, carried out through a series of activating (E1), conjugating (E2), and ligating (E3) enzymes. This process has been found to be overactive in various cancers, leading to increased oncogenic activities. Ubiquitin-conjugating enzyme 2 M (UBE2M) is one of two neddylation enzymes that play a vital role in this pathway. Studies have shown that targeting UBE2M in cancer treatment is crucial, as it regulates many molecular mechanisms like DNA damage, apoptosis, and cell proliferation. However, developing small molecule inhibitors against UBE2M remains challenging due to the lack of suitable druggable pockets. We have discovered that Micafungin, an antifungal agent that inhibits the production of 1,3-ß-D-glucan in fungal cell walls, acts as a neddylation inhibitor that targets UBE2M. Biochemical studies reveal that Micafungin obstructs neddylation and stabilizes UBE2M. In cellular experiments, the drug was found to interact with UBE2M, prevent neddylation, accumulate cullin ring ligases (CRLs) substrates, reduce cell survival and migration, and induce DNA damage in gastric cancer cells. This research uncovers a new anti-cancer mechanism for Micafungin, paving the way for the development of a novel class of neddylation inhibitors that target UBE2M.

Assessment of micafungin dosage regimens against Candida spp. in pediatric patients undergoing hematopoietic stem cell transplantation: a pharmacokinetic/pharmacodynamic analysis using Monte Carlo simulation.

The objective of this study was to evaluate the efficacy of various micafungin dosing regimens against Candida spp. in pediatric patients undergoing hematopoietic stem cell transplantation (HSCT). Monte Carlo simulations were conducted using pharmacokinetic (PK) parameters and pharmacodynamic (PD) data to determine the probabilities of target attainment and cumulative fractions of response in terms of area under the concentration curve/minimum inhibition concentration targets of micafungin. Current standard clinical micafungin dosing regimens of 1 and 2 mg/kg/day were appropriate for the prevention and treatment of Candida glabrata infection in pediatric patients undergoing HSCT, respectively. Moreover, the high-dose prophylactic dosage (2 mg/kg/day) and therapeutic dosage (4 mg/kg/day) should be the preferred option to optimize efficacy against Candida albicans. However, none of the simulated regimens was effective against Candida parapsilosis in pediatric HSCT patients. These PK/PD-based simulations rationalize and optimize the micafungin dosing regimens against Candida spp. in pediatric patients undergoing HSCT.

Development of an in vitro pharmacokinetic/pharmacodynamic model in the presence of serum for studying micafungin activity against Candida albicans: a need for revision of CLSI susceptibility breakpoints.

BACKGROUND: The CLSI breakpoint for micafungin and Candida albicans is 0.25 mg/L, higher than the CLSI epidemiological cut-off value (0.03 mg/L) whereas the EUCAST values are identical (0.016 mg/L). We developed a novel in vitro dialysis-diffusion pharmacokinetic/pharmacodynamic (PK/PD) model, confirmed correlation to in vivo outcome and studied micafungin pharmacodynamics against Canida albicans. METHODS: Four C. albicans isolates, including a weak (F641L) and a strong (R647G) fks1 mutants, were studied using a 104 cfu/mL inoculum and RPMI medium with and without 10% pooled human serum. The exposure-effect relationship fAUC0-24/MIC was described for CLSI and EUCAST methodology. Monte Carlo simulation analysis included standard (100 mg i.v.) and higher (150-300 mg) doses q24h to determine the corresponding probability of target attainment (PTA). RESULTS: The in vitro PK/PD targets for stasis/1-log kill were 36/57 fAUC0-24/MIC in absence and 2.8/9.2 fAUC0-24/MIC in the presence of serum, and similar for wild-type and fks mutant isolates. The PTAs for both PK/PD targets were high (>95%) for EUCAST susceptible isolates but not for CLSI susceptible non-wild-type isolates (CLSI MICs 0.06-0.25 mg/L). 300 mg q24h was needed to attain PK/PD targets for non-wild-type isolates with CLSI MICs 0.06-0.125 mg/L and EUCAST MICs 0.03-0.06 mg/L. CONCLUSION: The in vitro 1-log kill effect corresponded to stasis in animal model and mycological response in patients with invasive candidiasis, thereby validating the model for studying pharmacodynamics of echinocandins in vitro. EUCAST breakpoints were well supported by our findings but our data questions whether the current CLSI breakpoint, which is higher than the epidemiological cut-off values, is appropriate.

Echinocandin Resistance in Candida auris Occurs in the Murine Gastrointestinal Tract Due to FKS1 Mutations.

Candida auris is resistant to multiple antifungal agents. This study investigated its antifungal susceptibility and explored FKS1 mutations across the isolates from mice enterically colonized with wild-type C. auris and treated with echinocandin. Resistant C. auris with FKS1 mutations, including S639F, S639Y, D642Y, R1354H, or R1354Y, were isolated and found to be micafungin- and caspofungin-resistant in vivo; however, the MICs of isolates with mutation in R1354 remained below the micafungin breakpoint in vitro.

Antiviral Activity of Micafungin and Its Derivatives against SARS-CoV-2 RNA Replication.

Echinocandin antifungal drugs, including micafungin, anidulafungin, and caspofungin, have been recently reported to exhibit antiviral effects against various viruses such as flavivirus, alphavirus, and coronavirus. In this study, we focused on micafungin and its derivatives and analyzed their antiviral activities against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The micafungin derivatives Mi-2 and Mi-5 showed higher antiviral activity than micafungin, with 50% maximal inhibitory concentration (IC50) of 5.25 and 6.51 µM, respectively (3.8 to 4.7-fold stronger than micafungin) and 50% cytotoxic concentration (CC50) of >64 µM in VeroE6/TMPRSS2 cells. This high anti-SARS-CoV-2 activity was also conserved in human lung epithelial cell-derived Calu-3 cells. Micafungin, Mi-2, and Mi-5 were suggested to inhibit the intracellular virus replication process; additionally, these compounds were active against SARS-CoV-2 variants, including Delta (AY.122, hCoV-19/Japan/TY11-927/2021), Omicron (BA.1.18, hCoV-19/Japan/TY38-873/2021), a variant resistant to remdesivir (R10/E796G C799F), and a variant resistant to casirivimab/imdevimab antibody cocktail (E406W); thus, our results provide basic evidence for the potential use of micafungin derivatives for developing antiviral agents.

Serine/Threonine Phosphatase Calcineurin Orchestrates the Intrinsic Resistance to Micafungin in the Human-Pathogenic Fungus Mucor circinelloides.

Procedures such as solid-organ transplants and cancer treatments can leave many patients in an immunocompromised state. This leads to their increased susceptibility to opportunistic diseases such as fungal infections. Mucormycosis infections are continually emerging and pose a serious threat to immunocompromised patients. Recently there has been a sharp increase in mucormycosis cases as a secondary infection in patients battling severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Mucorales fungi are notorious for presenting resistance to most antifungal drugs. The absence of effective means to treat these infections results in mortality rates approaching 100% in cases of disseminated infection. One of the most effective antifungal drug classes currently available is the echinocandins. Echinocandins seem to be efficacious in the treatment of many other fungal infections. Unfortunately, susceptibility testing has found that echinocandins have little to no effect on Mucorales fungi. In this study, we found that the model Mucorales Mucor circinelloides genome carries three copies of the genes encoding the echinocandin target protein ß-(1,3)-d-glucan synthase (fksA, fksB, and fksC). Interestingly, we found that exposing M. circinelloides to micafungin significantly increased the expression of the fksA and fksB genes, resulting in an increased accumulation of ß-(1,3)-d-glucan on the cell walls. However, this overexpression of the fks genes is not directly connected to the intrinsic resistance. Subsequent investigation discovered that the serine/threonine phosphatase calcineurin regulates the expression of fksA and fksB, and the deletion of calcineurin results in a decrease in expression of all three fks genes. Deletion of calcineurin also results in a lower minimum effective concentration (MEC) of micafungin. In addition, we found that duplication of the fks gene is also responsible for the intrinsic resistance, in which lack of either fksA or fksB led a lower MEC of micafungin. Together, these findings demonstrate that calcineurin and fks gene duplication contribute to the intrinsic resistance to micafungin we observe in M. circinelloides.

Analysis of fks1 and fks2 gene mutations in invasive Candida glabrata strains from Pakistan.

INTRODUCTION: The gradual increase in caspofungin usage in Pakistan raises a concern of emergence of echinocandin resistance in local Candida glabrata strains. We sequenced and determined mutations in fks1 and fks2 genes in invasive Candida glabrata strains from Pakistan. MATERIAL AND METHODS: Thirty-six invasive C. glabrata strains were selected with median (min-max) minimum inhibitory concentrations (MICs) of 0.06 (0.015-0.25) mg/L for caspofungin, 0.015 (0.008-0.06) mg/L for micafungin and 0.06 (0.015-0.12) mg/L for anidulafungin. fks1 and fks2 gene fragments were sequenced using Sanger methodology. Sequences were analysed with MEGA-6 software to identify specific single-nucleotide polymorphisms (SNP) against wild-type sequences of C. glabrata. RESULTS: In fks1 gene, non-synonymous mutation D632H was observed in one isolate with caspofungin MIC of 0.25 mg/L. Synonymous mutation at position A742 was observed in 26/36 (72%) of the isolates. 34/36 (94.5%) isolates analysed for fks2 gene were observed as wild type. A novel non-synonymous mutation at I661T was observed in fks2 gene in one isolate with caspofungin MIC of 0.12 mg/L and anidulafungin and micafungin MIC of 0.06 and 0.015 mg/L, respectively. Novel fks2 synonymous mutations at position T647, K652 and I706 were observed in 16/36 (44%), 25/36 (69%) and 23/36 (63%) isolates, respectively. CONCLUSION: Low frequencies of both non-synonymous and synonymous polymorphisms were observed in invasive C. glabrata strains. Since S663P in fks2 gene is associated with caspofungin resistance, a novel mutation at 661 codon identified in our study needs correlation with treatment outcome data and mandates periodic genomic surveillance.

Anti-Candida auris activity in vitro and in vivo of micafungin loaded nanoemulsions.

Fungi are becoming increasingly resistant, especially the new strains. Therefore, this work developed nanoemulsions (NE) containing micafungin (MICA), in order to improve its action against infections caused by Candida auris. The NEs were composed of the surfactants polyoxyethylene (20) cetyl ether (Brij 58®)/soy phosphatidylcholine at 10%, sunflower oil/cholesterol at 10%, and 80% PBS. The NEs were characterized by Dynamic Light Scattering (DLS). For the microbiological in vitro evaluation the determination of the minimum inhibitory concentration (MIC), ergosterol/sorbitol, time kill and biofilms tests were performed. Additionally, the antifungal activity was also evaluated in a Galleria mellonella model. The same model was used in order to evaluate acute toxicity. The NE showed a size of ∼ 42.12 nm, a polydispersion index (PDI) of 0.289, and a zeta potential (ZP) of -3.86 mV. NEM had an average size of 41.29 nm, a PDI of 0.259, and a ZP of -4.71 mV. Finally, both nanoemulsions showed good stability in a storage period of 3 months. Although NEM did not show activity in planktonic cells, it exhibited action against biofilm and in the in vivo infection model. In the alternative in vivo model assay, it was possible to observe that both, NEM and free MICA at 0.2 mg/l, was effective against the infection, being that NEM presented a better action. Finally, NEM and free MICA showed no acute toxicity up to 4 mg/l. NEM showed the best activities in in vitro in mature antibiofilm and in alternative in vivo models in G. mellonella. Although, NEs showed to be attractive for MICA transport in the treatment of infections caused by C. auris in vitro and in vivo studies with G. mellonella, further studies should be carried out, in mice, for example.

Candida auris is a fungus that can cause infections in the human body. As it is a microorganism with a high potential for resistance, it is extremely important to develop new therapeutic alternatives. Thus, nanotechnology, the science that studies materials with extremely small sizes, can be considered a promising method in the treatment of these infections.

Activities of Manogepix and Comparators against 1,435 Recent Fungal Isolates Collected during an International Surveillance Program (2020).

We evaluated the in vitro activity of manogepix and comparator agents against 1,435 contemporary fungal isolates collected worldwide from 73 medical centers in North America, Europe, the Asia-Pacific region, and Latin America during 2020. Of the isolates tested, 74.7% were Candida spp.; 3.7% were non-Candida yeasts, including 27 Cryptococcus neoformans var. grubii (1.9%); 17.1% were Aspergillus spp.; and 4.5% were other molds. All fungal isolates were tested by reference broth microdilution according to CLSI methods. Based on MIC90 values, manogepix (MIC50/MIC90, 0.008/0.06 mg/liter) was 16- to 64-fold more active than anidulafungin, micafungin, and fluconazole against Candida spp. isolates and the most active agent tested. Similarly, manogepix (MIC50/MIC90, 0.5/1 mg/liter) was ≥8-fold more active than anidulafungin, micafungin, and fluconazole against C. neoformans var. grubii. Based on minimum effective concentration for 90% of the isolates tested (MEC90) and MIC90 values, manogepix (MEC90, 0.03 mg/liter) was 16- to 64-fold more potent than itraconazole, posaconazole, and voriconazole (MIC90s, 0.5 to 2 mg/liter) against 246 Aspergillus spp. isolates. Aspergillus fumigatus isolates exhibited a wild-type (WT) phenotype for the mold-active triazoles, including itraconazole (87.0% WT) and voriconazole (96.4% WT). Manogepix was highly active against uncommon species of Candida, non-Candida yeasts, and rare molds, including 11 isolates of Candida auris (MIC50/MIC90, 0.004/0.015 mg/liter) and 12 isolates of Scedosporium spp. (MEC50/MEC90, 0.06/0.12 mg/liter). Additional studies are in progress to evaluate the clinical utility of the manogepix prodrug fosmanogepix in difficult-to-treat resistant fungal infections.

A Mycobacterium tuberculosis-Infected Patient Who Could Not Tolerate Oral Intake Successfully Treated Using an Intravenous Tedizolid-Containing Regimen.

BACKGROUND Mycobacterium tuberculosis (M. tuberculosis) is usually treated by oral antimycobacterial agents, including rifampicin, ethambutol, and pyrazinamide, but the treatment regimen with intravenous and/or intramuscular antimycobacterial agents for patients who cannot take medications orally remains unclear. CASE REPORT A 77-year-old man with chronic renal failure had an esophageal-skin fistula after he had surgeries for removal of esophageal and gastric cancers and reconstruction using jejunum, and he showed a cavity, tree-in-bud formation, and pleural effusions in his left upper lung fields on his chest X-ray after treatment of cellulitis and bacteremia/candidemia by meropenem, teicoplanin, and micafungin. M. tuberculosis was isolated from his sputum and exudate fluid from the reconstructed esophageal-skin fistula. Although he could not take antimycobacterial agents orally, treatment was started with intravenous agents combining levofloxacin (LVFX) every other day, isoniazid (INH), and linezolid (LZD). However, his platelets were decreased 21 days after treatment started, and it was thought to be an adverse effect of LZD and/or INH. After changing LZD to tedizolid (TZD), in addition to changing from INH to intramuscular streptomycin twice per week, his platelet counts increased. Intravenous TZD could be continued, and it maintained his condition without exacerbations of thrombocytopenia and renal failure. The M. tuberculosis disappeared, and the abnormal chest X-ray shadows were improved 2 months after the start of treatment. CONCLUSIONS Administration of intravenous TZD, in addition to intravenous LVFX and intramuscular SM in combination, might be a candidate regimen for M. tuberculosis patients who cannot take oral medications.

Evaluation of the synergistic antifungal activity of micafungin and voriconazole plus sertraline against Candida auris.

Candida auris is an emerging global public health threat. It is an opportunistic yeast that usually affects critically ill patients in healthcare settings and is characterized by reduced susceptibility to multiple antifungal classes. Combination therapy with antifungals and repurposed drugs is a feasible alternative to overcome this problem. The aim of this study was to examine the in vitro interactions and potential synergy of micafungin (MFG) and voriconazole (VRC) plus the antidepressant sertraline (SRT) against clinical isolates of C. auris. Conventional antifungal testing was first performed with the three drugs according to the CLSI methodology. Drug interactions were determined by the checkerboard microdilution assay using the fractional inhibitory concentration (FIC) index. Synergistic interactions were noted with the combination of MFG and SRT plus VRC with FIC values of 0.37 to 0.49 for some strains. Indifferent interactions were observed when MFG was combined with SRT with just one exception (FIC 0.53). No antagonism was observed for any combination. The combination of VRC with MCF or SRT may be relevant for treating C. auris infections.

Evaluation of the Post-Antifungal Effect of Rezafungin and Micafungin against Candida albicans, Candida parapsilosis and Candida glabrata.

Rezafungin, a new echinocandin with an extended half-life, exhibits potent activity against Candida spp. Aside from the MIC, specific interactions between antifungal and isolate, including the duration of anti-infective activity, may impact dose interval choices and infection outcome. We evaluated rezafungin and micafungin post-antifungal effect (PAFE) against C. albicans, C. parapsilosis and C. glabrata. Six Candida spp. isolates were tested, including two of each species, C. albicans, C. parapsilosis and C. glabrata. Antifungal susceptibility testing was performed using the CLSI reference broth microdilution method. Antifungal concentrations of 1x, 4x and 16x the baseline MIC were used for PAFE determinations. Colony counts were performed at T0 (pre-exposure), after the 1-h drug exposure, after the cell wash (T1), and at T2, T4, T8, T12, T24 and T48 h. Rezafungin PAFE results were equivalent to micafungin PAFE values for one C. albicans (>14.9 h) and both C. glabrata (>40 h) isolates for all concentrations tested. The rezafungin and micafungin PAFEs could not be determined against one C. albicans isolate. Prolonged PAFE results were also noted for rezafungin (range, 18.4 to >40 h) against both C. parapsilosis isolates at all concentrations, while no micafungin PAFE or a short PAFE (range, 1.8 to 7.4 h) was observed against these organisms, except at 16x bMIC. Rezafungin showed sustained growth inhibition following drug removal and displayed equivalent or longer PAFE values than micafungin against all tested Candida spp.

Echinocandins Susceptibility Patterns of 2,787 Yeast Isolates: Importance of the Thresholds for the Detection of FKS Mutations.

Since echinocandins are recommended as first line therapy for invasive candidiasis, detection of resistance, mainly due to alteration in FKS protein, is of main interest. EUCAST AFST recommends testing both MIC of anidulafungin and micafungin, and breakpoints (BPs) have been proposed to detect echinocandin-resistant isolates. We analyzed MIC distribution for all three available echinocandins of 2,787 clinical yeast isolates corresponding to 5 common and 16 rare yeast species, using the standardized EUCAST method for anidulafungin and modified for caspofungin and micafungin (AM3-MIC). In our database, 64 isolates of common pathogenic species were resistant to anidulafungin, according to the EUCAST BP, and/or to caspofungin, using our previously published threshold (AM3-MIC ≥ 0.5 mg/L). Among these 64 isolates, 50 exhibited 21 different FKS mutations. We analyzed the capacity of caspofungin AM3-MIC and anidulafungin MIC determination in detecting isolates with FKS mutation. They were always identified using caspofungin AM3-MIC and the local threshold while some isolates were misclassified using anidulafungin MIC and EUCAST threshold. However, both methods misclassified four wild-type C. glabrata as resistant. Based on a large data set from a single center, the use of AM3-MIC testing for caspofungin looks promising in identifying non-wild-type C. albicans, C. tropicalis and P. kudiravzevii isolates, but additional multicenter comparison is mandatory to conclude on the possible superiority of AM3-MIC testing compared to the EUCAST method.

An in-vitro comparative study of the binding of caspofungin and micafungin to plasma proteins.

OBJECTIVES: Echinocandins are widely used for the treatment of invasive fungal diseases. While they bind strongly to plasma proteins, our knowledge of this process is not sufficient to permit their pharmacokinetics and pharmacodynamics targets to be discussed. In this study, we characterized the binding of two echinocandins, caspofungin and micafungin, to plasma proteins, human serum albumin (HSA) and human α 1-acid glycoprotein (AAG). METHODS: The binding parameters, number of binding sites (n) and association constant (K) for caspofungin and micafungin to HSA and AAG were determined by equilibrium dialysis. The binding site on HSA for these echinocandins was identified by conducting inhibition experiments. KEY FINDINGS: Caspofungin was found to bind strongly to a single site on HSA (n = 1.26, K = 0.45 × 106 M-1) and AAG (n = 0.99, K = 0.29 × 106 M-1). Micafungin was found to bind more strongly to HSA (n = 1.35, K = 1.44 × 106 M-1) and AAG (n = 1.32, K = 1.16 × 106 M-1). The binding site for these drugs on HSA appears to be within subdomain IA. CONCLUSIONS: Free fraction of caspofungin and micafungin in patients may not be substantially affected due to the contribution of AAG to the overall protein binding and the binding to subdomain IA on HSA, which is different from the major drug-binding sites within subdomains IB, IIA and IIIA.

Antifungal susceptibility profile of invasive Candida glabrata isolates (2009-2020) from a tertiary care hospital laboratory in Pakistan.

Introduction. Invasive infections with Candida glabrata are a global concern due to poor clinical outcomes and propensity to acquire resistance to antifungal agents. Hypothesis/Gap Statement. Monitoring emerging resistance and trends in Candida glabrata, an important agent of candidemia in Pakistan, is critical for patient management; data that is missing from Pakistan. Aim. Thus, this study evaluated antifungal resistance and MICs) distribution in invasive C. glabrata isolates from Pakistan. Methods. This cross-sectional and retrospective study was conducted from January 2009 to March 2020 at a clinical laboratory in Pakistan that has a nation-wide network. Antifungal susceptibility data of 277 candidemia, deep organ and soft tissue (invasive) C. glabrata sensu lato isolates against fluconazole, itraconazole, voriconazole, posaconazole, anidulafungin, micafungin, caspofungin and amphotericin B was retrieved. Susceptibility testing was performed using colorimetric broth microdilution and interpreted using CLSI criteria. Demographics, clinical history and outcome were studied. Chi-square test was used to demonstrate association between antifungal resistance and clinical characteristics of the patients. Results. We identified 277 patients with invasive C. glabrata infection. Of which 48 (18.4%) isolates were resistant to fluconazole (MIC ≥64 mg l-1), one isolate each was resistant to amphotericin (MIC=2 mg l-1), anidulafungin (MIC=1 mg l-1) and micafungin (MIC=0.5 mg l-1). MIC90 for fluconazole was 64 mg l-1 and other triazoles 2 mg l-1, caspofungin 0.12 mg l-1, anidulafungin 0.06 mg l-1, micafungin 0.03 mg l-1 and amphotericin 0.5 mg l-1. Fluconazole MIC ≥64 mg l-1, caspofungin MIC >0.06 mg l-1 and amphotericin MIC >0.25 mg l-1 (above MIC50) were significantly associated with patient being alive at the time of reporting, no use of healthcare devices, nor infection with other fungi. Fluconazole resistance was significantly associated with prior antifungal use by the patient. Conclusion. Surveillance data of antifungal resistance among common Candida species should be monitored closely for identification of resistant strains.