Antifungal drug penetration in soft tissue abscesses: a comparative analysis

BACKGROUND

Invasive fungal infections (IFIs) are severe and difficult-to-treat infections affecting immunocompromised patients. Antifungal drug penetration at the site of infection is critical for outcome and may be difficult to achieve. Data about antifungal drug distribution in infected human tissues under real circumstances of IFI are scarce.

METHODS

Multiple samples were obtained from soft tissue abscesses of a lung transplant patient with Candida albicans invasive candidiasis who underwent recurrent procedures of drainage, while receiving different consecutive courses of antifungal therapy [itraconazole (ITC), fluconazole, caspofungin]. Antifungal drug concentrations were measured simultaneously at the site of infection (surrounding inflammatory tissue and fluid content of the abscess) and in plasma for calculation of the tissue/plasma ratio (R). The concentration within the infected tissue was interpreted as appropriate if it was equal or superior to the MIC of the causal pathogen.

RESULTS

A total of 30 tissue samples were collected for measurements of ITC (n = 12), fluconazole (n = 17) and caspofungin (n = 1). Variable concentrations were observed in the surrounding tissue of the lesions with median R of 2.79 (range 0.51-15.9) for ITC and 0.94 (0.21-1.37) for fluconazole. Concentrations ranges within the fluid content of the abscesses were 0.39-1.83 for ITC, 0.66-1.02 for fluconazole and 0.23 (single value) for caspofungin. The pharmacodynamic target (tissue concentration ≥ MIC) was achieved in all samples for all three antifungal drugs.

CONCLUSIONS

This unique dataset of antifungal drug penetration in infected human soft tissue abscesses suggests that ITC, fluconazole and caspofungin could achieve appropriate concentrations in soft tissue abscesses.

Limitations of antifungal prophylaxis in preventing invasive Candida surgical site infections after liver transplant surgery

Invasive primary Candida surgical site infections (IP-SSIs) are a common complication of liver transplantation, and targeted antifungal prophylaxis is an efficient strategy to limit their occurrence. We performed a retrospective single-center cohort study among adult single liver transplant recipients at Duke University Hospital in the period between 1 January 2015 and 31 December 2020. The study aimed to determine the rate of Candida IP-SSI according to the peri-transplant antifungal prophylaxis received. Of 470 adult single liver transplant recipients, 53 (11.3%) received micafungin prophylaxis, 100 (21.3%) received fluconazole prophylaxis, and 317 (67.4%) did not receive systemic antifungal prophylaxis in the peri-transplant period. Ten Candida IP-SSIs occurred among 5 of 53 (9.4%) micafungin recipients, 1 of 100 (1.0%) fluconazole recipients, and 4 of 317 (1.3%) recipients who did not receive antifungal prophylaxis. Our study highlights the limitations of antifungal prophylaxis in preventing invasive Candida IP-SSI after liver transplant surgery. We hypothesize that pathogen, host, and pharmacokinetic-related factors contributed to the occurrence of Candida IP-SSI despite antifungal prophylaxis. Our study reinforces the need for a risk-based, multi-pronged approach to fungal prevention, including targeted antifungal administration in patients with risks for invasive candidiasis and close monitoring, especially among patients with surgically complex procedures, with timely control of surgical leaks.

Population pharmacokinetic modeling and target attainment analyses of rezafungin for the treatment of candidemia and invasive candidiasis

Rezafungin is a chemically and metabolically stable echinocandin with a longer half-life than other echinocandins, allowing for a once-weekly intravenous infusion versus a daily infusion. Rezafungin is approved in the US for the treatment of candidemia and/or invasive candidiasis and is in development for the prevention of invasive fungal disease caused by Candida, Aspergillus, and Pneumocystis spp. in immunosuppressed patients. A population pharmacokinetic (PPK) model was developed using data from five Phase 1, one Phase 2, and one Phase 3 study. The model found to best describe the available data was a three-compartment PPK model with first-order elimination characterized by the parameters clearance (CL), central volume (V1), peripheral volume (V23), intercompartmental clearance 1, and intercompartmental clearance 2. The variability model included correlated interindividual variability in CL, V1, and V23 and a proportional residual variability model. The following statistically significant covariates were identified: albumin concentrations on V23; body surface area (BSA) on CL, V1, and V23; and disease state on CL and V1. Disease states were defined as patients from the Phase 2 and Phase 3 studies and hepatically impaired subjects. Covariates of BSA, disease state, or albumin, included in the final model, were not associated with clinically meaningful changes in PK, nor were any other patient factors, indicating that a common dose regimen is adequate for all adult patients. Target attainment simulations were performed to estimate the probability of achieving PK/pharmacodynamic targets across the range of minimum inhibitory concentration values for six species of Candida.

Pharmacokinetic and pharmacodynamic considerations for antifungal therapy optimisation in the treatment of intra-abdominal candidiasis

Intra-abdominal candidiasis (IAC) is one of the most common of invasive candidiasis observed in critically ill patients. It is associated with high mortality, with up to 50% of deaths attributable to delays in source control and/or the introduction of antifungal therapy. Currently, there is no comprehensive guidance on optimising antifungal dosing in the treatment of IAC among the critically ill. However, this form of abdominal sepsis presents specific pharmacokinetic (PK) alterations and pharmacodynamic (PD) challenges that risk suboptimal antifungal exposure at the site of infection in critically ill patients. This review aims to describe the peculiarities of IAC from both PK and PD perspectives, advocating an individualized approach to antifungal dosing. Additionally, all current PK/PD studies relating to IAC are reviewed in terms of strength and limitations, so that core elements for the basis of future research can be provided.

Absence of Clinically Meaningful Drug-Drug Interactions with Rezafungin: Outcome of Investigations

Rezafungin is a novel once-weekly echinocandin for intravenous injection currently in development for the treatment of Candida infections and the prevention of Candida, Aspergillus, and Pneumocystis infections in allogeneic blood and marrow transplant recipients. While in vitro data indicated that rezafungin exposure was unlikely to be affected by commonly prescribed medicines, interactions resulting in the altered systemic exposure of some drugs coadministered with rezafungin could not be excluded. Two phase 1 open label crossover studies, conducted in healthy subjects, examined drug interactions between rezafungin and multiple drug probe cytochrome P450 (CYP) substrates and/or transporter proteins, immunosuppressants, and cancer therapies. Statistical analysis compared the outcomes for drugs coadministered with rezafungin to those for the drugs administered alone. The geometric mean ratio was reported, and a default 90% confidence interval (CI) no-effect equivalence range of 80 to 125% was used for the maximal plasma concentration (Cmax), the area under the curve from time zero to the final sampling time point (AUC0-t), and the AUC from time zero to infinity (AUC0-∞). Most probes and concomitant drugs were within the equivalence range. For tacrolimus, ibrutinib, mycophenolic acid, and venetoclax, the AUC or Cmax was reduced (10 to 19%), with lower bounds of the 90% CI values falling outside the no-effect range. The rosuvastatin AUC and Cmax and the repaglinide AUC0-∞ were increased (12 to 16%), with the 90% CI being marginally above the upper bound. Overall, the in vitro and in vivo data demonstrated a low drug interaction potential with rezafungin via CYP substrate/transporter pathways and commonly prescribed comedications, suggesting that coadministration was unlikely to result in clinically significant effects. Treatment-emergent adverse events were typically mild, and rezafungin was generally well tolerated. IMPORTANCE Antifungal agents used to treat life-threatening infections are often associated with severe drug-drug interactions (DDIs) that may limit their usefulness. Rezafungin, a newly approved once-weekly echinocandin, has been shown to be free of DDIs based on extensive nonclinical and clinical testing described in this study.

Pharmacokinetics of Voriconazole in Peritoneal Fluid of Critically Ill Patients

Data on the distribution of voriconazole (VRC) in the human peritoneal cavity are sparse. This prospective study aimed to describe the pharmacokinetics of intravenous VRC in the peritoneal fluid of critically ill patients. A total of 19 patients were included. Individual pharmacokinetic curves, drawn after single (first dose on day 1) and multiple (steady-state) doses, displayed a slower rise and lower fluctuation of VRC concentrations in peritoneal fluid than in plasma. Good but variable penetration of VRC into the peritoneal cavity was observed, and the median (range) peritoneal fluid/plasma ratios of the area under the concentration-time curve (AUC) were 0.54 (0.34 to 0.73) and 0.67 (0.63 to 0.94) for single and multiple doses, respectively. Approximately 81% (13/16) of the VRC steady-state trough concentrations (Cmin,ss) in plasma were within the therapeutic range (1 to 5.5 μg/mL), and the corresponding Cmin,ss (median [range]) in peritoneal fluid was 2.12 (1.39 to 3.72) μg/mL. Based on the recent 3-year (2019 to 2021) surveillance of the antifungal susceptibilities for Candida species isolated from peritoneal fluid in our center, the aforementioned 13 Cmin,ss in peritoneal fluid exceeded the MIC90 of C. albicans, C. glabrata, and C. parapsilosis (0.06, 1.00, and 0.25 μg/mL, respectively), which supported VRC as a reasonable choice for initial empirical therapies against intraabdominal candidiasis caused by these three Candida species, prior to the receipt of susceptibility testing results.

СRITERIA FOR ASSESSING ENDOGENOUS INTOXICATION IN PATIENTS WITH MULTIPLE PERITONITIS

OBJECTIVE

The aim: To determine the diagnostic significance of the level of malondialdehyde (MDA) in various biological media for RP for assessing and predicting the course of the disease.

PATIENTS AND METHODS

Materials and methods: Our study included The work was based on the results of surgical treatment of 60 patients with RP: according to MPI I - in 17 (28.3%), MPI II - in 23 (38.4%) and MPI III - in 20 (33.3%) patients. Surgical intervention for RP was aimed at sanitation and drainage of the abdominal cavity. The control group included 15 practi¬cally healthy people, whose blood and urine biochemical parameters served as the norm. According to the clinical course of the disease, the patients were divided depend on admission, The secondary product of lipid peroxidation - MDA was studied in blood serum, peritoneal exudate and urine in patients with RP, depending on the severity of the pathological process according to the Mannheim peritoneal index (MPI) - I severity (I), II severity (II), III severity (III). The work was based on the results of surgical treatment of 60 patients with RP: according to MPI I - in 17 (28.3%), MPI II - in 23 (38.4%) and MPI III - in 20 (33.3%) patients.

RESULTS

Results: Analyses of results showed that the average value of MDA in various biomedicals of recovered (n = 18) and subsequently died (n = 5) patients with MPI II are given in Table. 2. As can be seen from the presented data, the average value of MDA in blood serum and peritoneal exudate in patients with a lethal outcome is significantly higher than in those who have recovered. This fact indicates a more pronounced endogenous intoxication in patients who died from RP.

CONCLUSION

Conclusions: The content of MDA in the blood serum before surgery in patients with a lethal outcome was 190% (p <0.001). The level of MDA in urine in patients according to MPI II who subsequently died before surgery was 110% (p <0.001), and in those who recovered by 300% (p <0.001) it was higher than the norm. exudate taken during the operation averaged 4.14 ± 0.33 nmol / ml, then in the recovered - 2.89 ± 0.08 nmol / ml. A high level of MDA in the blood serum, peritoneal exudate with a decrease in the elimination of MDA in the urine in the postoperative period are prognostically unfavorable signs in patients, indicating the continuation of endogenous intoxication and a possible death.

Caspofungin Population Pharmacokinetic Analysis in Plasma and Peritoneal Fluid in Septic Patients with Intra-Abdominal Infections: A Prospective Cohort Study

OBJECTIVES

The aim of this study was to report the pharmacokinetics (PK) of caspofungin in plasma and peritoneal fluid and to identify optimal dosing strategies in septic patients with intra-abdominal infections.

METHODS

Eleven patients with secondary peritonitis with septic shock received the standard dosing regimen of caspofungin. Total caspofungin plasma and peritoneal concentrations were subject to a population PK analysis using Pmetrics^®. Monte Carlo simulations were performed considering the ratio of 24-h total drug exposure above the minimum inhibitory concentration (AUC₂₄/MIC) in plasma and comparing simulated concentrations versus MIC in peritoneal fluid.

RESULTS

Fat-free mass (FFM) was retained in the final model of caspofungin, reporting a total clearance (standard deviation) of 0.78 (0.17) L/h and a central volume of distribution of 9.36 (2.61) L. The peritoneal fluid/plasma ratio of caspofungin was 33% on the first day of therapy (AUC₂₄ 73.92 (21.93) and 26.03 (9.88) mg*h/L for plasma and peritoneal data, respectively). Dosing simulations supported the use of standard dosing regimens for patients with an FFM < 50 kg for the most susceptible candida species (C. albicans and C. glabrata). For higher FFM, a loading dose of 70 or 100 mg, with a maintenance dose of 70 mg, reached AUC₂₄/MIC ratios for these species.

CONCLUSIONS

There is moderate penetration of caspofungin into the peritoneal cavity (33%). For empirical treatment, a dose escalation of 100 mg loading dose on the first day is suggested for higher FFM to ensure adequate concentrations into the abdominal cavity for the most susceptible candida species.

A Loading Micafungin Dose in Critically Ill Patients Undergoing Continuous Venovenous Hemofiltration or Continuous Venovenous Hemodiafiltration: A Population Pharmacokinetic Analysis

BACKGROUND

In this study, the authors aimed to compare the pharmacokinetics (PK) of micafungin in critically ill patients receiving continuous venovenous hemofiltration (CVVH, 30 mL·kg-1·h-1) with those of patients receiving equidoses of hemodiafiltration (CVVHDF, 15 mL·kg-1·h-1 + 15 mL·kg-1·h-1) and determine the optimal dosing regimen using the developed model.

METHODS

Patients with septic shock undergoing continuous renal replacement therapy and receiving a conventional dose of 100 mg micafungin once daily were eligible for inclusion. Total micafungin plasma concentrations from 8 CVVH sessions and 8 CVVHDF sessions were subjected to a population PK analysis using Pmetrics. Validation of the model performance was reinforced by external validation. Monte Carlo simulations were performed considering the total ratio of free drug area under the curve (AUC) over 24 hours to the minimum inhibitory concentration (MIC) (AUC0-24/MIC) in plasma.

RESULTS

The median total body weight (min-max) was 94.8 (66-138) kg. Micafungin concentrations were best described by a 2-compartmental PK model. No covariates, including continuous renal replacement therapy modality (CVVH or CVVHDF), were retained in the final model. The mean parameter estimates (SD) were 0.96 (0.32) L/h for clearance and 14.8 (5.3) L for the central compartment volume. External validation confirmed the performance of the developed PK model. Dosing simulations did not support the use of standard 100 mg daily dosing, except for Candida albicans on the second day of therapy. A loading dose of 150 mg followed by 100 mg daily reached the probability of target attainment for all C. albicans and C. glabrata, but not for C. krusei and C. parapsilosis.

CONCLUSIONS

No difference was observed in micafungin PK between equidoses of CVVH and CVVHDF. A loading dose of 150 mg is required to achieve the PK/PD target for less susceptible Candida species from the first day of therapy.

Micafungin Population PK Analysis in Healthy and Septic Pigs: Can the Septic Porcine Model Predict the Micafungin PK in Septic Patients?

OBJECTIVES

To describe micafungin pharmacokinetic (PK) alterations of sepsis induced in piglets and to determine whether the porcine septic model is able to predict the PK of micafungin in septic patients at the plasma and peritoneal sites.

METHODS

From healthy (n = 8) and septic piglet group (n = 16), total micafungin concentrations were subject to a population PK analysis using Monolix®. Data from 16 septic humans patients from others studies was used to compare micafungin PK between septic piglets and septic patients.

RESULTS

Sepsis induced in piglets slightly alters the total clearance and the volume of distribution, while inter-compartment clearance is increased (from 3.88 to 5.74 L/h) as well as the penetration into peritoneal cavity (from 61 to 90%). In septic human patients, PK parameters are similar except for the Vd, which is corrected by an allometric factor based on the body weight of each species. Micafungin penetration into peritoneal cavity of humans is lower than in septic piglets (40 versus 90%).

CONCLUSIONS

The sepsis induced in the porcine model alters the PK of micafungin comparable to that in humans. In addition, micafungin PK is similar between these two species at the plasma level taking into account the allometric relationship of the body weight of these species on the central volume of distribution. The porcine septic plasma model would be able to predict the micafungin PK in the septic patients. However, further studies on peritoneal penetration are necessary to characterize this inter-species difference.

Antifungal Susceptibility Testing Identifies the Abdominal Cavity as a Source of Candida glabrata-Resistant Isolates

To identify unrecognized niches of resistant Candida isolates and compartmentalization, we retrospectively studied the antifungal susceptibility of 1,103 Candida spp. isolates from blood cultures, nonblood sterile samples, and nonsterile samples. Antifungal susceptibility was assessed by EUCAST E.Def 7.3.2; sequencing and genotyping of the fks1-2 and erg11 genes were carried out for non-wild-type isolates. Resistance compartmentalization (presence of resistant and susceptible isogenic isolates in different anatomical sites of a given patient) was studied. Clinical charts of patients carrying non-wild-type isolates were reviewed. Most isolates (63%) were Candida albicans, regardless the clinical source; Candida glabrata (27%) was the second most frequently found species in abdominal cavity samples. Fluconazole and echinocandin resistance rates were 1.5 and 1.3%, respectively, and were highest in C. glabrata. We found 22 genotypes among non-wild-type isolates, none of them widespread across the hospital. Fluconazole/echinocandin resistance rates of isolates from the abdominal cavity (3.2%/3.2%) tended to be higher than those from blood cultures (0.7%/1.3%). Overall, 15 patients with different forms of candidiasis were infected by resistant isolates, 80% of whom had received antifungals before or at the time of isolate collection; resistance compartmentalization was found in six patients, mainly due to C. glabrata. The highest antifungal resistance rate was detected in isolates from the abdominal cavity, mostly C. glabrata. Resistance was not caused by the spread of resistant clones but because of antifungal treatment. Resistance compartmentalization illustrates how resistance might be overlooked if susceptibility testing is restricted to bloodstream isolates.

Assessment of Micafungin Dosage Regimens in Patients with Cancer Using Pharmacokinetic/Pharmacodynamic Modeling and Monte Carlo Simulation

Micafungin is widely used for invasive candidiasis, especially in critically ill patients and those with cancer, and for empirical antifungal therapy in patients with neutropenic fever. This is the first study to investigate the pharmacokinetics and disposition parameters of micafungin in patients with cancer. In this observational pharmacokinetic study, blood samples were collected and analyzed using high-performance liquid chromatography. Pharmacokinetic parameters were estimated using Monolix 4.4 software. The plasma micafungin concentrations were measured in a total of 133 samples from 19 patients. In the final two-compartment model with linear elimination, the estimated micafungin clearance (CL) was significantly higher in patients with cancer than in those without cancer (1.2 vs. 0.6 L/h, p = 0.012), whereas other parameters did not significantly differ between the two groups. Aspartate and alanine transaminases and body weight significantly influenced micafungin CL in patients, with and without cancer. Overall, the probability of target attainment increased with increasing doses and decreased with higher MICs in both groups. In simulations, the patients without cancer achieved higher pharmacokinetic/pharmacodynamic targets with a 90% probability for all simulated doses, compared to the patients with cancer. Micafungin demonstrated dose-proportional linear pharmacokinetics in both the patients with and those without cancer. The estimated micafungin CL was significantly higher in patients with cancer, suggesting a need for increased dosage, especially for Candida spp. with high MICs, in these patients. Further studies should assess the efficacy and optimum dosage of micafungin for the treatment and prevention of febrile neutropenia (FN) in patients with cancer.

Pharmacokinetics/Pharmacodynamics of caspofungin in plasma and peritoneal fluid of liver transplant recipients

Background: The weaker diffusion of echinocandins in the peritoneal fluid (PF) could promote Candida resistant isolates. The aim of this study was to analyse the pharmacokinetics/pharmacodynamics (PK/PD) of caspofungin in plasma and PF of liver transplant recipients.Methods: Liver transplant patients received caspofungin as postoperative prophylaxis. Caspofungin concentrations were quantified in plasma and in PF on Days 1, 3 and 8. Data were analysed using non-linear mixed-effect modelling and Monte Carlo simulations. Area under curve (AUC) in plasma and PF were simulated under three dosing regimens. Probabilities of target attainment (PTA) were calculated using fAUC_0-24/minimal inhibitory concentration (MIC) ratios with MICs ranging from 0.008 to 8 mg/litre. All the patients included were monitored weekly for Candida colonisation and for Candida infections.Results: Twenty patients were included. Median daily dose of caspofungin was 0.81 mg/kg. Plasma (n=395) and peritoneal (n=50) concentrations at steady state were available. A two-compartment model with first-order absorption and elimination was described. Our two-compartment model with first-order absorption and elimination model produced an effective PK/PD relationship in plasma, achieving a PTA ≥90% and MIC ranging from 0.008 to 0.12 mg/L for C. albicans and glabrata. In PF, PTAs at D8 were only optimal for a MIC of 0.008 in patients weighing 60 kg under the three dosing regimens. Among the 16 patients colonized, all MIC values were below the maximal concentration (Cmax) in plasma but not in PF.Conclusion: Peritoneal concentrations of caspofungin were low. Simulations showed that the PTA for Candida spp. in PF were not optimal, that might suggesting a potential risk of resistance.

Emerging of Fatal Colitis with Multidrug-Resistant Candida glabrata after Small Bowel Transplantation

Background

Small bowel transplantation is a potential option for patients with intestinal-failure, and the incidences of infections caused by Candida species that are more resistant to antifungal drugs are increasing in these patients. In this manuscript, we reported a case of fatal colitis after small bowel transplantation induces by multidrug-resistant (MDR) Candida glabrata. Case Presentation. A 52-year-old man has undergone an extensive small bowel resection with the length of the remaining bowel which was less than 40 cm who became a candidate for transplantation. Four months after transplantation, the patient experienced severe bloody diarrhea with abdominal distension. Ileoscopy and colonoscopy did not show neither pathological change and rejection nor cytomegalovirus (CMV) infection posttransplantation. Abdomen computed tomography showed diffuse moderate small bowel wall thickening. After detection of budding yeast in the stool samples, stool culture was positive for Candida, DNA was extracted, and ITS1-5.8s-ITS2 region of the fungal agent was amplified. Sequencing analysis of PCR and antifungal susceptibility testing revealed that this isolate was multidrug-resistant C. glabrata. Besides, there was no evidence for other pathogens known to cause infection in various laboratory tests. Immediate antifungal treatments with caspofungin remained unsuccessful, and on the eighteenth day of admission, the patient expires with septic shock.

Conclusion

These findings highlight the challenging management of candidiasis in patients with small bowel transplantation. Infectious diseases due to MDR organisms have emerged as a vital clinical problem in this patient population.

Breakthrough invasive fungal infections in liver transplant recipients exposed to prophylaxis with echinocandins vs other antifungal agents: A systematic review and meta-analysis

INTRODUCTION

Although echinocandins are recommended as first-line prophylaxis for high-risk orthotopic liver transplant (OLT) recipients, occurrence of breakthrough-invasive fungal infections (IFIs) remains a serious concern. We aim to assess the risk of breakthrough IFIs among OLT recipients exposed to prophylaxis with echinocandins compared to other antifungals.

MATERIALS AND METHODS

Two authors independently searched PubMed-MEDLINE, Embase, study registries and reference lists from inception to March 2021, to retrieve randomised controlled trials (RCTs) or observational studies comparing efficacy and safety of echinocandins vs other antifungals for prophylaxis in OLT recipients. Data were independently extracted from two authors, and the quality of included studies was independently assessed according to ROB 2.0 tool for RCTs and ROBINS-I tool for observational studies. The primary outcome was occurrence of breakthrough IFI at the end of prophylaxis (EOP).

RESULTS

698 articles were screened, and ten studies (3 RCTs and 7 observational) were included. No difference between echinocandins and other antifungals in terms of breakthrough IFIs at the EOP emerged both from RCTs (odds ratio [OR] 0.85, 95% CI 0.24-2.99) and observational studies (OR 1.43, 95% CI 0.28-7.40). No difference emerged also for secondary outcomes. In the subgroup comparison between echinocandins and polyenes, a trend for higher risk of breakthrough IFI at the EOP (OR 4.82, 95% CI 0.97-24.03) was noted.

CONCLUSIONS

Echinocandins do not seem to be associated with increased risk of breakthrough IFIs in OLT recipients. However, the large diversity in the comparator group hinders a definitive interpretation. Further studies exploring the relationship between echinocandin use and breakthrough IFIs according to specific comparators are warranted.

Pharmacokinetics and Antifungal Activity of Echinocandins in Ascites Fluid of Critically Ill Patients

The pharmacokinetics and antifungal activity of the echinocandins anidulafungin (AFG), micafungin (MFG), and caspofungin (CAS) were assessed in ascites fluid and plasma of critically ill adults treated for suspected or proven invasive candidiasis. Ascites fluid was obtained from ascites drains or during paracentesis. The antifungal activity of the echinocandins in ascites fluid was assessed by incubation of Candida albicans and Candida glabrata at concentrations of 0.03 to 16.00 μg/ml. In addition, ascites fluid samples obtained from our study patients were inoculated with the same isolates and evaluated for fungal growth. These patient samples had to be spiked with echinocandins to restore the original concentrations because echinocandins had been lost during sterile filtration. In ascites fluid specimens of 29 patients, echinocandin concentrations were below the simultaneous plasma levels. Serial sampling in 20 patients revealed a slower rise and decline of echinocandin concentrations in ascites fluid than in plasma. Proliferation of C. albicans in ascites fluid was slower than in culture medium and growth of C. glabrata was lacking, even in the absence of antifungals. In CAS-spiked ascites fluid samples, fungal CFU counts moderately declined, whereas spiking with AFG or MFG had no relevant effect. In ascites fluid of our study patients, echinocandin concentrations achieved by therapeutic doses did not result in a consistent eradication of C. albicans or C. glabrata. Thus, therapeutic doses of AFG, MFG, or CAS may result in ascites fluid concentrations preventing relevant proliferation of C. albicans and C. glabrata, but do not warrant reliable eradication.

Prospective Cohort Study of Micafungin Population Pharmacokinetic Analysis in Plasma and Peritoneal Fluid in Septic Patients with Intra-abdominal Infections

The objective of this study was to describe the pharmacokinetics (PK) of micafungin in plasma and peritoneal fluid in septic patients with intra-abdominal infections. Twelve patients with secondary peritonitis in septic shock receiving 100 mg micafungin once daily were included. Total micafungin plasma and peritoneal fluid were subjected to a population pharmacokinetic analysis using Pmetrics. Monte Carlo simulations were performed considering the total area under the curve from 0 to 24 h (AUC_0-24)/MIC ratios in plasma. Micafungin concentrations in both plasma and the peritoneal exudate were best described by a three-compartmental PK model with the fat-free mass (FFM) as a covariate of clearance (CL) and the volume of the central compartment (V_c). The mean parameter estimates (standard deviations [SD]) were 1.18 (0.40) liters/h for CL and 12.85 (4.78) liters for V_c. The mean peritoneal exudate/plasma ratios (SD) of micafungin were 25% (5%) on day 1 and 40% (8%) between days 3 and 5. Dosing simulations supported the use of standard 100-mg daily dosing for Candida albicans (FFM, <60 kg), C. glabrata (FFM, <50 kg), and C. tropicalis (FFM, <30 kg) on the second day of therapy. There is a moderate penetration of micafungin into the peritoneal cavity (25 to 40%). For empirical treatment, a dose escalation of at least a loading dose of 150 mg depending on the FFM of patients and the Candida species is suggested to be effective from the first day of therapy.

Nebulized Micafungin Treatment for Scopulariopsis/Microascus Tracheobronchitis in Lung Transplant Recipients

Scopulariopsis/Microascus isolates cause infections with high mortality in lung transplant recipients. Treatment is challenging due to antimicrobial resistance. We describe two cases of Scopulariopsis/Microascus tracheobronchitis in lung transplant recipients successfully treated with nebulized micafungin. This antifungal was well tolerated and achieved high concentrations in epithelial lining fluid up to 14 h after nebulization without significant plasma concentrations. Nebulized micafungin may be a safe and effective option for the treatment of fungal tracheobronchitis.

Caspofungin pharmacokinetics and probability of target attainment in ICU patients in China

OBJECTIVES

Effective antifungal therapy is important to reduce mortality in patients with invasive fungal infections (IFIs). Numerous factors affect pharmacokinetic/pharmacodynamic (PK/PD) parameters in critically-ill patients. To guide individualised administration in critically-ill patients, it is of great significance to determine the population pharmacokinetics of caspofungin.

METHODS

A prospective study in 42 ICU patients with IFIs was conducted in China. A population pharmacokinetic model of caspofungin was established using a non-linear mixed-effects model, which was utilised to investigate the effects of demographic indices, liver function and kidney function on pharmacokinetics. Additionally, appropriate dosages of caspofungin under various scenarios were determined based on MICs and probability of target attainment (PTA) at specific dosages.

RESULTS

In critically-ill Chinese patients, clearance (CL), volume of distribution (V) and area under the curve at steady-state (AUC_ss) of caspofungin were 0.32 L/h, 6.77 L and 135.47 mg•h/L, respectively. Blood albumin and total bilirubin levels were factors affecting CL, while body weight was the only factor affecting V among Chinese people with relatively low weight compared with other populations. A maintenance dose of 50 mg caspofungin achieved a high PTA for treating IFIs caused by Candida albicans (MIC ≤ 0.06 mg/L) and Candida glabrata (MIC ≤ 0.125 mg/L). The maintenance dose of caspofungin should be adjusted to 70-200 mg for IFIs caused by C. albicans (MIC, 0.06-0.125 mg/L). For IFIs caused by Candida parapsilosis, an MIC > 0.03 mg/L is associated with a very low PTA, but higher doses of caspofungin or alternative antifungals need to be further studied.

CONCLUSION

The population pharmacokinetic model established here described well the PK/PD characteristics of caspofungin in critically-ill Chinese patients. These results could guide the formulation of individualised caspofungin dosing regimens for critically-ill patients.

Ebola virus antibody decay-stimulation in a high proportion of survivors

Neutralizing antibody function provides a foundation for the efficacy of vaccines and therapies^1–3. Here, using a robust in vitro Ebola virus (EBOV) pseudo-particle infection assay and a well-defined set of solid-phase assays, we describe a wide spectrum of antibody responses in a cohort of healthy survivors of the Sierra Leone EBOV outbreak of 2013–2016. Pseudo-particle virus-neutralizing antibodies correlated with total anti-EBOV reactivity and neutralizing antibodies against live EBOV. Variant EBOV glycoproteins (1995 and 2014 strains) were similarly neutralized. During longitudinal follow-up, antibody responses fluctuated in a ‘decay–stimulation–decay’ pattern that suggests de novo restimulation by EBOV antigens after recovery. A pharmacodynamic model of antibody reactivity identified a decay half-life of 77–100 days and a doubling time of 46–86 days in a high proportion of survivors. The highest antibody reactivity was observed around 200 days after an individual had recovered. The model suggests that EBOV antibody reactivity declines over 0.5–2 years after recovery. In a high proportion of healthy survivors, antibody responses undergo rapid restimulation. Vigilant follow-up of survivors and possible elective de novo antigenic stimulation by vaccine immunization should be considered in order to prevent EBOV viral recrudescence in recovering individuals and thereby to mitigate the potential risk of reseeding an outbreak.

In many survivors of Ebola virus infection, antibody responses show long-term patterns of decline followed by restimulation, possibly owing to recrudescence of persisting virus.

Rezafungin versus Caspofungin in a Phase 2, Randomized, Double-Blind Study for the Treatment of Candidemia and Invasive Candidiasis- The STRIVE Trial

Background

Rezafungin (RZF) is a novel echinocandin exhibiting distinctive pharmacokinetics/pharmacodynamics. STRIVE was a phase 2, double-blind, randomized trial designed to compare the safety and efficacy of RZF once weekly (QWk) to caspofungin (CAS) once daily for treatment of candidemia and/or invasive candidiasis (IC).

Methods

Adults with systemic signs and mycological confirmation of candidemia and/or IC were randomized to RZF 400 mg QWk (400 mg), RZF 400 mg on week 1 then 200 mg QWk (400/200 mg), or CAS 70 mg as a loading dose followed by 50 mg daily for ≤4 weeks. Efficacy assessments included overall cure (resolution of signs of candidemia/IC + mycological eradication) at day 14 (primary endpoint), investigator-assessed clinical response at day 14, and 30-day all-cause mortality (ACM) (secondary endpoints), and time to negative blood culture. Safety was evaluated by adverse events and ACM through follow-up.

Results

Of 207 patients enrolled, 183 were in the microbiological intent-to-treat population (~21% IC). Overall cure rates were 60.5% (46/76) for RZF 400 mg, 76.1% (35/46) for RZF 400/200 mg, and 67.2% (41/61) for CAS; investigator-assessed clinical cure rates were 69.7% (53/76), 80.4% (37/46), and 70.5% (43/61), respectively. In total, 30-day ACM was 15.8% for RZF 400 mg, 4.4% for RZF 400/200 mg, and 13.1% for CAS. Candidemia was cleared in 19.5 and 22.8 hours in RZF and CAS patients, respectively. No concerning safety trends were observed; ACM through follow-up was 15.2% (21/138) for RZF and 18.8% (13/69) for CAS.

Conclusions

RZF was safe and efficacious in the treatment of candidemia and/or IC.

Clinical Trials Registration

NCT02734862

Pharmacokinetics of echinocandins in suspected candida peritonitis: A potential risk for resistance

INTRODUCTION

A possible increase in Candida resistance, especially in Candida glabrata, has been speculated according to poor diffusion of echinocandins to peritoneal fluid.

MATERIALS/METHODS

Peritoneal and serum concentrations of caspofungin, micafungin and anidulafungin were analysed in surgical patients with suspected candida peritonitis. After 4 days of starting therapy, serum and peritoneal samples (through peritoneal drainage) were obtained at baseline, 1, 6, 12 and 24 h of drug administration. Micafungin and anidulafungin concentrations were determined using high-performance liquid chromatography (HPLC/F), whereas caspofungin concentrations were established by bioassay.

RESULTS

Twenty-three critically ill patients with suspected abdominal fungal infection who were receiving an echinocandin were prospectively recruited. No specific criteria were applied to prescribe one specific echinocandin. No special clinical differences were observed among the three groups of patients. All were receiving antibiotic therapy, 80% required inotropic drugs, and fungal peritonitis was confirmed in 74% of them. The AUC_{0_24h} (mg × h/L) obtained in serum and peritoneal fluid were: 126.84 and 34.38, 98.52 and 18.83, and 66.9 and 8.78 for anidulafungin, micafungin and caspofungin, respectively. The median concentration in peritoneal fluid ranged from 0.66 to 1.82 μg/mL for anidulafungin, 0.68-0.88 μg/mL for micafungin and 0.21-0.46 μg/mL for caspofungin.

CONCLUSION

The results showed moderate penetration of echinocandins into the peritoneal fluid of these patients. These levels are below the threshold of resistance mutant selection published by other authors. This could justify a potential risk of resistance in patients with prolonged treatment with echinocandins and suboptimal control of abdominal infection.

Challenges in Antifungal Therapy in Diabetes Mellitus

Diabetic patients have an increased propensity to Candida sp. infections due to disease-related immunosuppression and various other physiological alterations. The incidence of candidiasis has increased in number over the years and is linked to significant morbidity and mortality in critically ill and immunosuppressed patients. Treatment of infection in diabetic patients may be complicated due to the various disease-related changes to the pharmacokinetics and pharmacodynamics (PK/PD) of a drug, including antifungal agents. Application of PK/PD principles may be a sensible option to optimise antifungal dosing regimens in this group of patients. Further studies on PK/PD of antifungals in patients with diabetes mellitus are needed as current data is limited or unavailable.

Pharmacokinetics of TKM-130803 in Sierra Leonean patients with Ebola virus disease: plasma concentrations exceed target levels, with drug accumulation in the most severe patients

Background

TKM-130803 is a specific anti-EBOV therapeutic comprised of two small interfering RNAs (siRNA) siLpol-2 and siVP35-2. The pharmacokinetics (PK) of these siRNAs was defined in Ebola virus disease (EVD) patients, with reference to efficacy (ET) and toxicology thresholds (TT). The relationship between PK and patient survival was explored.

Methods

Pharmacokinetic (PK) and pharmacodynamic (PD) data were available for seven participants with EVD in Sierra Leone who received 0·3 mg/kg of TKM-130803 by intravenous infusion over 2 h daily for up to 7 days. Plasma concentration of siRNA was compared to survival at 14 days. PK data were fitted to two-compartment models then Monte Carlo simulated PK profiles were compared to ET (Cmax 0·04–0·57 ng/mL and mean concentration 1·43 ng/mL), and TT (3000 ng/mL).

Findings

Viral loads (VL) were not significantly different at treatment onset or during treatment (p = 0·1) in subjects who survived or died. siRNA was in quantitative excess of virus genomes throughout treatment, but the 95% percentile exceeded TT. The maximum AUC for which the 95% percentile remained under TT was a continuous infusion of 0·15 mg/kg/day. Plasma concentration of both siRNAs were higher in subjects who died compared to subjects who survived (p<0·025 both siRNAs).

Interpretation

TKM-130803 was circulating in molar excess of circulating virus; a level considered needed for efficacy. Given extremely high viral loads it seems likely that the patients died because they were physiologically beyond the point of no return. Subjects who died exhibited some indication of impaired drug clearance, justifying caution in dosing strategies for such patients. This analysis has given a useful insight into the pharmacokinetics of the siRNA in the disease state and illustrates the value of designing PKPD studies into future clinical trials in epidemic situations.

Funding

This work was supported by the Wellcome Trust of Great Britain (grant number 106491/Z/14/Z and 097997/Z/11/A) and by the EU FP7 project PREPARE (602525). The PHE laboratory was funded by the UK Department for International Development. The funders had no role in trial design, data collection or analysis. The views expressed are those of the authors and not necessarily those of Public Health England, the Department of Health, or the EU.

Trial registration

Pan African Clinical Trials Registry PACTR201501000997429.

Quantification of anidulafungin and micafungin in human body fluids by high performance-liquid chromatography with UV-detection

The echinocandins anidulafungin (ANID) and micafungin (MICA) are recommended for treatment of invasive Candida infections. As target-site concentrations of antimicrobial agents are crucial for eradication of pathogens, we established and validated high-performance liquid chromatography-UV detection (HPLC-UV) assays for quantification of ANID and MICA in human plasma, ascites fluid, pleural effusion, and in cerebrospinal fluid (CSF). Sample pre-purification was performed by protein precipitation with acetonitrile followed by solid phase extraction. For both assays, intra- and interday precision, and accuracy fulfilled the requirements for bioanalytical methods issued by the European Medicine Agency (EMA). The lower limit of quantification was 0.01 mg/L for both drugs. At 25 °C, ANID and MICA concentrations declined by up to 70% within 24 h. Concentrations remained stable over 24 h at 4 °C and over four weeks at -80 °C. In conclusion, the developed methods are fit for the assessment of target-site pharmacokinetics of ANID and MICA in clinical studies.

Clinical and Laboratory Development of Echinocandin Resistance in Candida glabrata: Molecular Characterization

The pathogenic yeast Candida glabrata has become a public health issue due to the increasing number of echinocandin resistant clinical strains reported. In this study, acquisition and development of resistance to this antifungal class were studied in serial C. glabrata isolates from five patients admitted in two Spanish hospitals with a resistant profile against echinocandins associated with different mutations in hot-spot 1 of FKS2 gene. For two of these patients susceptible FKS wild-type isolates obtained prior to resistant ones were also investigated. Isolates were genotyped using multilocus sequence typing and microsatellite length polymorphism techniques, which yielded comparable results. Susceptible and resistant isolates from the same patient had the same genotype, being sequence type (ST) 3 the most prevalent among them. Isolates with different FKS mutations but the same ST were present in the same patient. MSH2 gene alterations were also studied to investigate their correlation with antifungal resistance acquisition but no association was found with antifungal resistance nor with specific genotypes. In vitro exposure to increasing concentrations of micafungin to susceptible isolates developed colonies carrying FKS mutations in agar plates containing a minimum concentration of 0.06 mg/L of micafungin after less than 48 h of exposure. We investigated the correlation between development of resistance and genotype in a set of susceptible strains after being in vitro exposed to micafungin and anidulafungin but no correlation was found. Mutant prevention concentration values and spontaneous growth frequencies after selection with both echinocandins were statistically similar, although FKS mutant colonies were more abundant after micafungin exposure (p < 0.001). Mutation S663P and F659 deletion were the most common ones found after selection with both echinocandins.

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.

Clinical Pharmacokinetics and Pharmacodynamics of Micafungin

Micafungin is a selective inhibitor of the synthesis of fungal 1,3-β-d-glucan, an essential component of the fungal cell wall. It is available as a powder for infusion only and is registered for the treatment of invasive and esophageal candidiasis in addition to prophylaxis of Candida infections in both adults and children. Average exposure after a single intravenous 100 mg dose in healthy adults is 133 mg h/L. Both exposure and maximum plasma concentration show linear dose proportional pharmacokinetics (PK) over a 0.15–8 mg/kg dose range. In healthy adults, the clearance (CL) is 10.4 mL/h/kg and volume of distribution is 0.2 L/kg; both are independent of the dose. Micafungin is metabolized by arylsulfatase, catechol-O-methyltransferase, and several cytochrome P450 (CYP) isoenzymes (3A4, 1A2, 2B6 and 2C), but no dose adjustments are necessary in patients with (severe) hepatic dysfunction. Exposure to micafungin is lower in hematology patients, and is even further lowered in critically ill patients (including burn patients) compared with healthy volunteers, which might have consequences for treatment efficacy. In children, an increased CL has been reported: 40–80 mL/h/kg in premature neonates and 20 mL/h/kg in children >4 months of age. Therefore, relatively higher doses of 4–10 mg/kg in premature neonates and 2–4 mg/kg in children with invasive candidiasis are used. However, these higher CLs may also be explained by the eightfold higher free fraction of unbound micafungin in premature neonates, meaning that an augmented dose might not be required.

ESICM/ESCMID task force on practical management of invasive candidiasis in critically ill patients

INTRODUCTION

The term invasive candidiasis (IC) refers to both bloodstream and deep-seated invasive infections, such as peritonitis, caused by Candida species. Several guidelines on the management of candidemia and invasive infection due to Candida species have recently been published, but none of them focuses specifically on critically ill patients admitted to intensive care units (ICUs).

MATERIAL AND METHODS

In the absence of available scientific evidence, the resulting recommendations are based solely on epidemiological and clinical evidence in conjunction with expert opinion. The task force used the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach to evaluate the recommendations and assign levels of evidence. The recommendations and their strength were decided by consensus and, if necessary, by vote (modified Delphi process). Descriptive statistics were used to analyze the results of the Delphi process. Statements obtaining > 80% agreement were considered to have achieved consensus.

CONCLUSIONS

The heterogeneity of this patient population necessitated the creation of a mixed working group comprising experts in clinical microbiology, infectious diseases and intensive care medicine, all chosen on the basis of their expertise in the management of IC and/or research methodology. The working group's main goal was to provide clinicians with clear and practical recommendations to optimize microbiological diagnosis and treatment of IC. The Systemic Inflammation and Sepsis and Infection sections of the European Society of Intensive Care Medicine (ESICM) and the Critically Ill Patients Study Group of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) therefore decided to develop a set of recommendations for application in non-immunocompromised critically ill patients.

Invasive fungal infection in crtically ill patients: hurdles and next challenges

A narrative review from a multidisciplinary task force of experts in critical care medicine and clinical mycology was carried out. The multi drug-resistant species Candida auris has emerged simultaneously on several continents, causing hospital outbreaks, especially in critically ill patients. Although there are not enough data to support the routine use of continuous antibiotic prophylaxis in patients subjected to extracorporeal membrane oxygenator, a clear increase of invasive fungal infection (IFI) has been described with the use of this device. Possible IFI treatment failures could be related with suboptimal antifungal concentrations despite dose adjustment. Invasive aspergillosis has become an important life-threating infection in intensive care unit related with new risk factors described. IFI remain important problem in critical patients due to the appearance of new risk factors, new species, and resistance increase. Multidisciplinary packages of measures designed to reduce IFI incidence and improve diagnostics tools may reduce the high mortality associated.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Low and constant micafungin concentrations may be sufficient to lead to resistance mutations in FKS2 gene of Candida glabrata

We studied the ability of five echinocandin-susceptible C. glabrata isolates to acquire in vitro resistance to anidulafungin and micafungin. All isolates became phenotypically resistant after 2-4 days of exposure to low and constant micafungin concentrations (P < .05). Mutations in the HS1 region of the FKS2 gene were found in all isolates. The acquisition of resistance was not related to the previous use of antifungal treatment in the patients or the presence of mutations at MSH2 gene. We found differences (P < .0001) in the median survival of Galleria mellonella larvae infected with FKS2 mutant isolates (5 days) and wild-type isolates (3 days).

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.

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.

Anidulafungin Pharmacokinetics in Ascites Fluid and Pleural Effusion of Critically Ill Patients

Anidulafungin concentrations were quantified with high-pressure liquid chromatography (HPLC) and UV detection of the ascites fluid and pleural effusion of 10 adult critically ill patients. Samples were collected from ascites fluid and from pleural drains or during paracentesis and thoracentesis, respectively. Anidulafungin levels in ascites fluid (0.12 to 0.99 μg/ml) and in pleural effusion (0.32 to 2.02 μg/ml) were below the simultaneous levels in plasma (1.04 to 7.70 and 2.48 to 13.36 μg/ml, respectively) and below the MIC values for several pathogenic Candida strains.

Mutant Prevention Concentration and Mutant Selection Window of Micafungin and Anidulafungin in Clinical Candida glabrata Isolates

We report the mutant prevention concentration (MPC) and mutant selection window (MSW) for micafungin and anidulafungin administered to treat Candida glabrata We also determine the mutation frequency. We studied 20 echinocandin-susceptible, fluconazole-intermediate, and FKS wild-type C. glabrata isolates. Adjusted inocula were stroked directly onto Sabouraud agar plates containing different concentrations of micafungin or anidulafungin and visually inspected daily for up to 5 days of incubation. Individual colonies growing on the plates containing echinocandins at 1 mg/liter were selected for antifungal susceptibility testing. The FKS genes of the resulting individual phenotypically resistant colonies were sequenced, and the MPC, MSW, and mutation frequency were determined. Biofilm was quantified, and the growth kinetics and virulence (Galleria mellonella model) of the resulting individual FKS mutant colonies were studied. For micafungin and anidulafungin, we found similar results for the MPC (0.06 to 2 mg/liter and 0.25 to 2 mg/liter, respectively), MSW (0.015 to 2 mg/liter for both echinocandins), and mutation frequency (3.7 × 10-8 and 2.8 × 10-8, respectively). A total of 12 isolates were able to grow at 1 mg/liter on echinocandin-containing plates, yielding a total of 32 phenotypically resistant colonies; however, FKS2 mutations (ΔF658, S663P, W715L, and E655A) were observed only in 21 colonies. We did not find differences in biofilm formation, the kinetic parameters studied, or the median survival of larvae infected by wild-type isolates and the resulting individual FKS2 mutant colonies. Echinocandin concentrations lower than 2 mg/liter can lead to selection of resistance mutations in C. glabrata isolates in vitro.

Pharmacokinetic study of anidulafungin in ICU patients with intra-abdominal candidiasis

Background

Only limited pharmacokinetic data are available for anidulafungin in ICU patients, especially in patients treated for severe intra-abdominal infection (IAI).

Methods

This was a prospective multicentre observational study in ICU patients with suspected yeast IAI. All patients received an intravenous loading dose of 200 mg of anidulafungin, followed by 100 mg/day. Thirteen blood samples were drawn between day 1 and day 5 for pharmacokinetic analysis. Samples were analysed by an HPLC-tandem MS method. Demographics and SAPS2 and SOFA scores were recorded.

Results

Fourteen patients with a median age (IQR) of 62 years (48-70) and with a mean BMI of 30.5 kg/m 2 were included from three centres; 57.1% were women. Their median (IQR) SAPS2 score was 54 (45-67) and their median (IQR) SOFA score was 8 (7-12). Six patients with community-acquired IAI and eight patients with nosocomial-acquired IAI were included. Twelve yeasts were isolated: six Candida albicans , two Candida glabrata , two Candida tropicalis , one Candida parapsilosis and one Candida krusei . Pharmacokinetic parameters were as follows [mean (% coefficient of variation)]: C max (mg/L) = 6.0 (29%); T max (h) = 1.6 (25.8%); C min (mg/L) = 3.2 (36.8%); AUC 0-24 (mg·h/L) = 88.9 (38.6%); t 1/2 (h) = 42.1 (68.2%); CL (L/h) = 1.2 (42.3%); and V (L) = 72.8 (87.8%). A two-compartment model best described the anidulafungin concentrations in the population pharmacokinetic study.

Conclusions

The pharmacokinetic parameters of anidulafungin in critically ill ICU patients with complicated IAI are similar to those observed in the literature. However, an increased V and a longer t 1/2 were observed in this study. (EudraCT No. 2010-018695-25).

Pharmacokinetic Properties of Micafungin in Critically Ill Patients Diagnosed with Invasive Candidiasis

The estimated attributable mortality rate for invasive candidiasis (IC) in the intensive care unit (ICU) setting varies from 30 to 40%. Physiological changes in critically ill patients may affect the distribution and elimination of micafungin, and therefore, dosing adjustments might be mandatory. The objective of this study was to determine the pharmacokinetic parameters of micafungin in critically ill patients and assess the probability of target attainment. Micafungin plasma concentrations were measured to estimate the pharmacokinetic properties of micafungin. MIC values for Candida isolates were determined to assess the probability of target attainment for patients. Data from 19 patients with suspected or proven invasive candidiasis were available for analysis. The median area under the concentration-time curve from 0 to 24 h at steady state (AUC_0-24) was 89.6 mg · h/liter (interquartile range [IQR], 75.4 to 113.6 mg · h/liter); this was significantly lower than the median micafungin AUC_0-24 values of 152.0 mg · h/liter (IQR, 136.0 to 162.0 mg · h/liter) and 134.0 mg · h/liter (IQR, 118.0 to 148.6 mg · h/liter) in healthy volunteers (P = <0.0001 and P = <0.001, respectively). All Candida isolates were susceptible to micafungin, with a median MIC of 0.016 mg/liter (IQR, 0.012 to 0.023 mg/liter). The median AUC_0-24/MIC ratio was 5,684 (IQR, 4,325 to 7,578), and 3 of the 17 evaluable patients (17.6%) diagnosed with proven invasive candidiasis did not meet the AUC/MIC ratio target of 5,000. Micafungin exposure was lower in critically ill patients than in healthy volunteers. The variability in micafungin exposure in this ICU population could be explained by the patients' body weight. Our findings suggest that healthier patients (sequential organ failure assessment [SOFA] score of <10) weighing more than 100 kg and receiving 100 mg micafungin daily are at risk for inappropriate micafungin exposure and potentially inadequate antifungal treatment. (This study has been registered at ClinicalTrials.gov under identifier NCT01716988.).

Albendazole and antibiotics synergize to deliver short-course anti-Wolbachia curative treatments in preclinical models of filariasis

Filarial nematode infections, caused by Wuchereria bancrofti, Brugia malayi (elephantiasis), and Onchocerca volvulus (river blindness) infect 150 million of the world’s poorest populations and cause profound disability. Standard treatments require repetitive, long-term, mass drug administrations and have failed to interrupted transmission in certain sub-Saharan African regions. A drug cure using doxycycline, which targets the essential filarial endosymbiont Wolbachia, is clinically effective but programmatically challenging to implement due to long treatment durations and contraindications. Here we provide proof-of-concept of a radical improvement of targeting Wolbachia via identification of drug synergy between the anthelmintic albendazole and antibiotics. This synergy enables the shortening of treatment duration of macrofilaricidal anti-Wolbachia based treatments from 4 wk to 7 d with registered drugs ready for clinical testing.

Elimination of filariasis requires a macrofilaricide treatment that can be delivered within a 7-day period. Here we have identified a synergy between the anthelmintic albendazole (ABZ) and drugs depleting the filarial endosymbiont Wolbachia, a proven macrofilaricide target, which reduces treatment from several weeks to 7 days in preclinical models. ABZ had negligible effects on Wolbachia but synergized with minocycline or rifampicin (RIF) to deplete symbionts, block embryogenesis, and stop microfilariae production. Greater than 99% Wolbachia depletion following 7-day combination of RIF+ABZ also led to accelerated macrofilaricidal activity. Thus, we provide preclinical proof-of-concept of treatment shortening using antibiotic+ABZ combinations to deliver anti-Wolbachia sterilizing and macrofilaricidal effects. Our data are of immediate public health importance as RIF+ABZ are registered drugs and thus immediately implementable to deliver a 1-wk macrofilaricide. They also suggest that novel, more potent anti-Wolbachia drugs under development may be capable of delivering further treatment shortening, to days rather than weeks, if combined with benzimidazoles.

Population Pharmacokinetic Model and Pharmacokinetic Target Attainment of Micafungin in Intensive Care Unit Patients

OBJECTIVE

To study the pharmacokinetics of micafungin in intensive care patients and assess pharmacokinetic (PK) target attainment for various dosing strategies.

METHODS

Micafungin PK data from 20 intensive care unit patients were available. A population-PK model was developed. Various dosing regimens were simulated: licensed regimens (I) 100 mg daily; (II) 100 mg daily with 200 mg from day 5; and adapted regimens 200 mg on day 1 followed by (III) 100 mg daily; (IV) 150 mg daily; and (V) 200 mg daily. Target attainment based on a clinical PK target for Candida as well as non-Candida parapsilosis infections was assessed for relevant minimum inhibitory concentrations [MICs] (Clinical and Laboratory Standards Institute). Parameter uncertainty was taken into account in simulations.

RESULTS

A two-compartment model best fitted the data. Clearance was 1.10 (root square error 8%) L/h and V 1 and V 2 were 17.6 (root square error 14%) and 3.63 (root square error 8%) L, respectively. Median area under the concentration-time curve over 24 h (interquartile range) on day 14 for regimens I-V were 91 (67-122), 183 (135-244), 91 (67-122), 137 (101-183) and 183 (135-244) mg h/L, respectively, for a typical patient of 70 kg. For the MIC/area under the concentration-time curve >3000 target (all Candida spp.), PK target attainment was >91% on day 14 (MIC 0.016 mg/L epidemiological cut-off) for all of the dosing regimens but decreased to (I) 44%, (II) 91%, (III) 44%, (IV) 78% and (V) 91% for MIC 0.032 mg/L. For the MIC/area under the concentration-time curve >5000 target (non-C. parapsilosis spp.), PK target attainment varied between 62 and 96% on day 14 for MIC 0.016.

CONCLUSIONS

The licensed micafungin maintenance dose results in adequate exposure based on our simulations with a clinical PK target for Candida infections but only 62% of patients reach the target for non-C. parapsilosis. In the case of pathogens with an attenuated micafungin MIC, patients may benefit from dose escalation to 200 mg daily. This encourages future study.

Unraveling Drug Penetration of Echinocandin Antifungals at the Site of Infection in an Intra-abdominal Abscess Model

Intra-abdominal candidiasis (IAC) is a prominent invasive fungal infection associated with high mortality. Prompt antifungal therapy and source control are crucial for successful treatment. Echinocandin antifungal drugs are first-line agents; however, their clinical effectiveness is highly variable, with known potential for breakthrough resistance, and little is known about drug exposure at the site of infection. Using matrix-assisted desorption ionization mass spectrometry imaging technology, we investigated the spatial and quantitative distribution in tissue lesions for two echinocandin drugs, micafungin and CD101, in a clinically relevant IAC mouse model. Drug accumulation within lesions was observed with both drugs at their humanized therapeutic doses. CD101, but not micafungin, accumulated in lesions at levels above the mutant prevention concentration of the infecting strain. These findings indicate that current echinocandin drugs are limited by penetration at the site of infection and have implications for clinical outcomes and emergence of resistance in patients with IAC.

Pharmacokinetics of antifungal drugs: practical implications for optimized treatment of patients

Introduction

Because of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.

Materials and methods

This review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.

Conclusions and discussion

Amphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

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.