Caspofungin Concentrations Research Articles

The echinocandin caspofungin impairs the innate immune mechanism against Candida parapsilosis

Since caspofungin inhibits fungal cell wall β-glucan synthesis and the fungal cell wall plays an important role in the recognition of Candida by phagocytic cells, we studied phagocytosis in the presence of caspofungin. The aim of this work was to investigate the effect of pre-treatment of Candida parapsilosis with caspofungin on phagocytic mechanisms (opsonisation, oxidative burst, phagocytosis and killing). C. parapsilosis grown in the presence of caspofungin at concentrations above the minimal inhibitory concentration (MIC) were more difficult to opsonise and to phagocytose. C. parapsilosis exposed to any concentration of caspofungin below and above the MIC was more difficult to kill. Caspofungin-treated C. parapsilosis impaired the oxidative burst. Overall, it appears that caspofungin treatment of C. parapsilosis alters the capacity of polymorphonuclear leukocytes to phagocytose and delays killing of the organism. This may allow C. parapsilosis to persist in tissues.

Successful treatment of Candida spp. encephalitis occurring under Caspofungin treatment after allogeneic stem cell transplantation

Dear Editor, Caspofungin belongs to standard drugs for empirical antifungal therapy (A1 recommendation) [1]. Breakthrough fungal infections are rare complications under treatment of neutropenic fever with Caspofungin [2]. However, emergence of candidiasis under treatment with Caspofungin was reported in poorly penetrated organs [3]. Drug concentrations of Caspofungin are sub-optimal in brain tissue [4]. Cerebral fungal infections are rare but life-threatening complications after allogeneic stem cell transplantation. Early diagnosis and critical monitoring of response to the chosen antifungal agents is critical for successful treatment. We report about the diagnosis and treatment of a 69-year-old female patient who underwent allogeneic peripheral blood stem cell transplant from a related donor against AML M2 developed out of MDS. Conditioning comprised of TBI 2Gy, Fludarabin 120 mg/m, ATG 40 mg/kg, Cyclophosphamid 120 mg/kg. Immunosuppression was accomplished by Ciclosporin A and Mycophenolat Mofetil. The patient did not completely engraft. Six months after transplantation, the patient developed pneumonia. As she did not improve under treatment with piperacillin or combactam and teicoplanin, we added caspofungin after 72 h. Hereunder, she improved tremendously. After 4 weeks, she developed ataxia and dysarthria. The cranial magnetic resonance imaging (MRI) showed two lesions most likely to be of infectious origin in the left parietal lobe and in the cerebellum (Fig. 1). Candida polymerase chain reaction of the liquor was positive. A second liquor puncture confirmed this result. Treatment was initiated with liposomal Amphothericin B 3 mg/d/kg intravenous and Voriconazol 200 mg twice a day per os. Within 2 weeks, all clinical symptoms resolved andwithin 4 weeks, the control MRI showed remission. Treatment with Voriconazol was continued for 6 weeks. In part, Candida breakthrough infections may be due to the changing scope of strains [5]. However, to our knowledge, only a few cases of candida breakthrough infections under Caspofungin are reported [3–9]. Krogh-Madson et al. isolated Caspofungin resistant C. glabrata from a critically ill liver transplant patient [6]. In another case C. parapsilosis infection emerged under co-administration of phenytoin maybe leading to decreased Caspofungin concentrations [6]. Mougdal et al. showed by molecular-genetic studies that one initial susceptible Candida glabrata strain acquired resistance to Caspofungin under therapy [9]. As penetration of caspofungin in Ann Hematol (2009) 88:93–94 DOI 10.1007/s00277-008-0551-3

Time-kill studies investigating the killing activity of caspofungin against Candida dubliniensis: comparing RPMI-1640 and antibiotic medium 3

We evaluated the in vitro activity of caspofungin against Candida dubliniensis strains using MIC and minimum fungicidal concentration (MFC) measurements and time-kill methodology. We used six C. dubliniensis clinical isolates and the CD 36 type strain. MICs and MFCs of caspofungin were determined using the standard broth microdilution method with normal (10(3) cells/mL) and elevated (10(5) cells/mL) starting inocula in RPMI-1640 and antibiotic medium 3 (AM3). MIC was determined after 24 h, and plating for MFC determination was performed after 48 h. In time-kill tests, all strains were tested at 0.06-16 mg/L caspofungin concentrations in RPMI-1640 and AM3. In RPMI-1640, the MIC range was 0.06-8 mg/L. Trailing growth was observed regardless of the starting inoculum after 48 h, but not after 24 h. In AM3 regardless of starting inoculum, MICs were 0.03 mg/L. After 48 h, trailing was not detected; two isolates grew at a concentration of 8 mg/L using 10(5) cells/mL as the starting inoculum [paradoxical growth (PG)]. All MFCs in RPMI-1640 and AM3 were >8 and < or =0.12 mg/L, respectively. In AM3, all but a single isolate showed PG in the MFC tests. Time-kill tests confirmed the results obtained by MFC tests both in RPMI-1640 and AM3. In vitro activity of caspofungin against C. dubliniensis depended on the starting inoculum and medium used. Using AM3 eliminated trailing from MIC determinations but not PG in MIC, MFC and time-kill tests.

Comparative In Vitro Pharmacodynamics of Caspofungin, Micafungin, and Anidulafungin against Germinated and Nongerminated Aspergillus Conidia

The concentration-dependent effects of echinocandins on the metabolic activity of Aspergillus spp. were comparatively studied by using nongerminated and germinated conidia. The susceptibilities of 11 Aspergillus fumigatus, 8 A. terreus and 8 A. flavus isolates to caspofungin, micafungin, and anidulafungin were studied by a CLSI (formerly NCCLS) M38-A broth microdilution-based method. After 48 h of incubation the minimum effective concentration (MEC) was defined microscopically. Metabolic activity was assessed by the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assay and modeled by using the sigmoid (E max) or "bell-shaped" model. The median MEC values of caspofungin (0.5 to 1 microg/ml), micafungin (0.06 to 0.12 microg/ml), and anidulafungin (0.03 microg/ml) against nongerminated conidia increased by 0 to 1, 1 to 2, and 2 to 3 twofold dilutions, respectively (depending on the species), over those against germinated conidia. A similar shift to the right was demonstrated for the corresponding curves of metabolic activity. There was a significant correlation between the degrees of maximal metabolic inhibition caused by different echinocandins at both the species level (greater inhibition for A. flavus) and the strain level (r = 0.84 to 0.93; P < 0.0001). Paradoxical increases in metabolism in the presence of higher concentrations of caspofungin, micafungin, and anidulafungin were detected in 6, 2, and 5 of the A. fumigatus isolates, respectively; 5, 1, and 2 of the A. terreus isolates, respectively; and 1, 0, and 0 of the A. flavus isolates, respectively. Based on the model, 50% of the maximal paradoxical increase was detected with 4.2, 11.1, and 10.8 microg/ml of caspofungin, micafungin, and anidulafungin, respectively. All echinocandins therefore exerted comparable levels of maximal metabolic inhibition against Aspergillus spp. at concentrations that were differentially increased for germinated versus nongerminated conidia. The paradoxical increase in metabolism occurred more frequently and at lower concentrations with caspofungin than with micafungin and anidulafungin.

In Vitro Study of Candida tropicalis Isolates Exhibiting Paradoxical Growth in the Presence of High Concentrations of Caspofungin

Paradoxical growth was noted in RPMI 1640 and antibiotic medium 3 in the case of 14 and 1 of 15 Candida tropicalis strains, respectively, at a caspofungin concentration of 12.5 microg/ml using minimum fungicidal concentration tests. Time-kill assays showed that against isolates killed at lower concentrations, caspofungin at a concentration of 12.5 microg/ml was only fungistatic.

Effect of Caspofungin on Metabolite Profiles of Aspergillus Species Determined by Nuclear Magnetic Resonance Spectroscopy

Invasive aspergillosis remains a potentially life-threatening infection, the incidence of which is increasing. Current methods used to determine the susceptibilities of Aspergillus strains to antifungal drugs are often unreliable. Nuclear magnetic resonance (NMR) spectroscopy can identify the metabolic complement of microorganisms while monitoring nutrient utilization from the incubation medium. We used 600-MHz (1)H NMR spectroscopy to monitor the metabolic responses of five Aspergillus species cultured in RPMI 1640-2% glucose-morpholinepropanesulfonate buffer to various concentrations of the antifungal drugs amphotericin B (AMB) and caspofungin. The metabolic endpoint (MEP) was determined from nutrient and metabolite resonances, measured as a function of the drug concentration, and was defined as a > or =50% reduction in nutrient consumption or metabolite production. MICs were evaluated by a modification of Clinical and Laboratory Standards Institute broth microdilution method M27-A, and minimal effective concentrations (MECs) were determined by microscopic examination of fungal hyphae. For AMB, the MEPs coincided with the MICs. For caspofungin, the MEPs agreed with the MECs for several Aspergillus strains, but the effect of drug pressure was more complex for others. Expansion of the MEP definition to include any significant changes in metabolite production resulted in agreement with the MEC in most cases. Paradoxical metabolic responses were observed for several Aspergillus strains at either high or low caspofungin concentrations and for one Aspergillus terreus strain with AMB. NMR spectroscopy proved to be a powerful tool for detecting the subtle effects of drug pressure on fungal metabolism and has the potential to provide an alternative method for determining the susceptibilities of Aspergillus species to antifungal drugs.

Maintenance of Therapeutic Concentrations of Caspofungin after Temporary Treatment Interruption (48 Hours) in a Child with Invasive Aspergillosis

Caspofungin is an antifungal drug active as a rescue treatment for invasive aspergillosis in cancer patients (4), with a MIC level of 0.5 mg/liter (2) and a minimum target concentration of 1 mg/liter (5, 6). In adults, these levels are achieved after a loading dose of 70 mg on the first day, followed by 50 mg once a day in the following days (5), while in children, a dose of 50 mg/m2 without a loading dose is required (6). We observed an 8-year-old girl with a previous pulmonary aspergillosis following allogeneic hemopoietic stem cell transplant for Pearson's syndrome that relapsed concomitant with the development of posttransplant acute myeloblastic leukemia (1). The infection relapsed during liposomal amphotericin B secondary prophylaxis; voriconazole treatment was not feasible because of concomitant barbiturate therapy (3), and therefore, caspofungin at 50 mg/m2 (5) (i.e., 30 mg/day) was administered. The patient was in poor clinical and psychological condition and refused any hospital stay; therefore, after 8 days of in-hospital treatment, the patient was discharged for the weekend. No antifungal treatment was administered for two days, and then the patient was admitted again to restart therapy. Blood samples for the determination of caspofungin blood concentrations were taken on the last day of treatment (Friday) and the first day of restarting treatment (Monday), before (through) and 30 min after the end (peak) of caspofungin infusion. The samples were stored at −80°C and sent to the Department of Pharmacology of the University of Florence for the determination of caspofungin blood levels. Caspofungin concentrations were determined by high-pressure liquid chromatography (lowest sensitivity limit, 0.125 mg/liter). A Chromsep C8 4.6-by-250-mm 5-μm column preceded by an adequate precolumn was used for the analysis; a flow rate of 1.3 ml/min was used. The fluorescence detector excitation and emission wavelengths were set at 220 and 304 nm, respectively. The drug was isolated from the plasma by solid-phase extraction (5). The caspofungin levels that resulted were 6.7 mg/liter through and 11.5 mg/liter peak on the last day of treatment and 1.9 mg/liter through and 5.6 mg/liter peak on the first day of resumption of therapy. Even after a 48-h interruption, the caspofungin blood concentration was above the required target concentration for the treatment of invasive aspergillosis (2, 5, 6). Even if further studies are needed to confirm this observation, our experience suggests that the administration of caspofungin for 5 days/week, after an adequate period (at least 1 week) of daily therapy, may be a possible approach for children with invasive aspergillosis who cannot receive other antifungal drugs and may not be hospitalized for some reason.

Paradoxical Growth Effect of Caspofungin Observed on Biofilms and Planktonic Cells of Five Different Candida Species

The paradoxical growth (PG) of Candida sp. biofilms in the presence of high caspofungin (CAS) concentrations was previously unknown. We sought to characterize the PG at supra-MICs of CAS among clinical Candida sp. isolates grown as biofilms in 96-well polystyrene microtiter plates. The MICs of CAS were determined for 30 clinical Candida sp. isolates (4 Candida albicans, 6 C. tropicalis, 7 C. parapsilosis, 8 C. orthopsilosis, and 5 C. metapsilosis isolates) when they were grown as planktonic cells and biofilms and were defined as the lowest drug concentrations that resulted in a prominent decrease in growth and a 50% reduction in metabolic activity, respectively. PG was defined as a resurgence of growth (>50% of that in the drug-free growth control well) at drug concentrations above the MIC. With the exception of C. tropicalis, all isolates displayed PG more frequently when they were grown as biofilms than when they grown as planktonic cells. PG was undetectable among C. metapsilosis isolates in planktonic cell MIC tests but was present in 100% of the isolates in biofilm MIC tests. The drug concentration and the number of drug dilutions supporting PG were higher for biofilms than for planktonic cells. Microscopic changes in cell morphology were observed among both planktonic and biofilm cells with PG. Specifically, the accumulation of enlarged, globose cells was associated with PG, and we hypothesize that CAS-induced changes in the cell wall composition may be the explanation.

Factors influencing caspofungin plasma concentrations in patients of a surgical intensive care unit

Co-morbidity, medical and surgical interventions often cause alterations to drug plasma concentrations and pharmacokinetic parameters in critically ill patients. In the present study, we investigated parameters influencing plasma caspofungin concentrations in patients of a surgical intensive care unit (SICU). In a monocentre open study, caspofungin trough concentrations (C(24)) were determined for a group of SICU patients. A linear-mixed model was then used to assess factors influencing caspofungin plasma concentrations. A total of 40 SICU patients were enrolled. Age and body weight ranged from 22 to 76 years and 47 to 108 kg, respectively. All participants received a caspofungin loading dose of 70 mg and a maintenance dose of 50 mg/day. The median duration of therapy was 10 days. Caspofungin C(24) in SICU patients varied more than those determined for healthy subjects reported in previous studies (0.52-4.08 microg/mL versus 1.12-1.78 microg/mL). According to our model, caspofungin C(24) were predicted to be significantly higher in patients with body weight <75 kg (P=0.019) and patients with albumin concentration >23.6 g/L (P=0.030). Our results show that body weight and albumin concentration influence caspofungin C(24) in SICU patients and should therefore be considered prognostic factors.

Concentration-Dependent Synergy and Antagonism within a Triple Antifungal Drug Combination againstAspergillusSpecies: Analysis by a New Response Surface Model

Triple antifungal combinations are used against refractory invasive aspergillosis without an adequate understanding of their pharmacodynamic interactions. We initially studied the in vitro triple combination of voriconazole, amphotericin B, and caspofungin against Aspergillus fumigatus, A. flavus, and A. terreus by a spectrophotometric microdilution broth method after 48 h of incubation. We then analyzed these results with a recently described nonlinear mixture response surface E(max)-based model modified to assess pharmacodynamic interactions at various growth levels. The new model allows flexibility in all four parameters of the E(max) model and is able to describe complex pharmacodynamic interactions. Concentration-dependent pharmacodynamic interactions were found within the triple antifungal combination. At the 50% growth level, synergy (median interaction indices of 0.43 to 0.82) was observed at low concentrations of voriconazole (<0.03 mg/liter) and amphotericin B (</=0.20 mg/liter) and at intermediate concentrations of caspofungin (0.95 to 14.88 mg/liter), whereas antagonism (median interaction indices of 1.17 to 1.80) was found at higher concentrations of voriconazole and amphotericin B. Ternary plot and interaction surface analysis further revealed the complexity of these concentration-dependent interactions. With increasing concentrations of amphotericin B, the synergistic interactions of voriconazole-caspofungin double combination decreased while the antagonistic interactions increased. A similar effect was observed when voriconazole was added to the double combination of amphotericin B and caspofungin. In conclusion, the new nonlinear mixture-amount response surface modeling of the triple antifungal combination demonstrated a net antagonism or synergy against Aspergillus species depending upon drug concentrations and species.

Induction of a high affinity fibronectin receptor inCandida albicansby caspofungin: requirements for β (1,6) glucans and the developmental regulator Hbr1p

Candida albicans expresses at least two biochemically distinct fibronectin receptors. Hemoglobin induces expression of a low affinity receptor recognizing the fibronectin cell-binding domain, whereas growth in complex media induces a high affinity receptor recognizing the collagen-binding domain. We now show that sub-inhibitory concentrations of caspofungin and nikkomycin Z, but not fluconazole, induce the high affinity fibronectin receptor in a dose-dependent manner. Macromolecular complexes mechanically sheared from caspofungin-treated cells retained high affinity fibronectin binding that was sensitive to protease, disulfide reduction, and beta (1,3) glucanase digestion. The high affinity fibronectin receptor was not inducible in a Kre9 mutant strain of C. albicans deficient in beta (1,6) glucans. Conversely, a mutant strain lacking the fibronectin binding protein Als5p showed no defects in induction of high or low affinity fibronectin receptors. Heterozygous mutants of a regulator of white-opaque phenotypic switching, HBR1, lacked any detectable high affinity fibronectin receptor expression in response to caspofungin, and re-introduction of the gene restored activity. Therefore, sub-inhibitory dosages of caspofungin induce a high affinity fibronectin receptor that is distinct from the known receptor Als5p and is dependent on beta (1,6) glucans and HBR1.

Ocular penetration of caspofungin in a rabbit uveitis model

Little is known about the ocular penetration of echinocandin antifungals. We studied the ocular distribution of systemically administered caspofungin in a rabbit uveitis model. Caspofungin (1 mg/kg per day) was given intravenously to rabbits as a single dose or as repeated daily doses on 7 days starting 24 h after induction of unilateral uveitis by intravitreal endotoxin injection. Caspofungin concentrations were determined by high-performance liquid chromatography in the cornea, aqueous humor, vitreous humor, and serum 4, 8, 16, and 24 h after administration of a single dose and 24 h after the last of seven doses. The mean caspofungin concentration in the aqueous of the inflamed eye 4 and 8 h after single-dose administration was 1.30 +/- 0.39 microg/ml and 1.12 +/- 0.34 microg/ml, respectively. Drug concentrations decreased to 0.24 +/- 0.09 microg/ml at 16 h and 0.26 +/- 0.14 microg/ml at 24 h. In the vitreous of inflamed eyes drug levels were undetectable at all time points. No drug was found in the aqueous of inflamed eyes 24 h after the last of seven repeated doses, and the vitreous only contained trace amounts. In the corneas of inflamed eyes concentrations reached 1.64 +/- 0.48 microg/g at 4 h, peaked at 2.16 +/- 1.14 microg/g at 8 h, and declined to 1.87 +/- 0.52 microg/g and 1.49 +/- 0.48 microg/g at 16 and 24 h, respectively. After repeated dosing, corneal concentrations of caspofungin were 0.8 and 1.0 microg/g and below the limit of detection in two of four animals. In non-inflamed eyes no drug was detectable in the aqueous and vitreous humor, and the corneas at any time point. In our model, caspofungin reached therapeutically relevant levels in the aqueous and cornea but not in the vitreous humor of inflamed eyes. Intraocular drug deposition was critically dependent on a disrupted blood-eye barrier. These findings suggest a limited role for caspofungin in the treatment of fungal endophthalmitis.

Antifungal interactions within the triple combination of amphotericin B, caspofungin and voriconazole against Aspergillus species

The in vitro effects of caspofungin combined with voriconazole and amphotericin B were tested in triplicate experiments against nine clinical isolates of Aspergillus fumigatus, Aspergillus flavus and Aspergillus terreus. The isolates were tested against a range of concentrations of voriconazole (0.015-1.0 mg/L), caspofungin (0.125-256 mg/L) and five concentrations of amphotericin B (0.1-0.5 mg/L) with a microdilution chequerboard method based on the CLSI M38-A reference method and the results were analysed with the fractional inhibitory concentration (FIC) index. The effect of individual drugs on the FIC index of each of the double combinations was also evaluated. The triple combination of voriconazole, caspofungin and amphotericin B against all Aspergillus spp. was synergistic (FIC index 0.49-0.57) at low median concentrations of amphotericin B (0.10-0.22 mg/L) and voriconazole (0.07-0.15 mg/L) over a wide range of caspofungin concentrations (4.32-17.28 mg/L). Antagonistic interactions (FIC index 1.65-2.15) were found at higher median concentrations of amphotericin B (0.3-0.5 mg/L) and voriconazole (0.23-0.68 mg/L) over a similarly wide range of caspofungin concentrations (1.47-32 mg/L). These concentration-dependent interactions may have important clinical implications, which require further evaluation in animal models of invasive aspergillosis.

In Vitro Susceptibilities to Caspofungin and Micafungin of Clinical Isolates of Candida Species

Caspofungin and micafungin are echinochandins with potent activities against Candida species. However, in vitro susceptibility to these agents of clinical Candida isolates in Korea has not been fully surveyed. We determined minimum inhibitory concentrations (MICs) of caspofungin and micafungin against clinical isolates of Candida species. A total of 107 blood isolates of Candida species (24 C. albicans, 25 C. tropicalis, 24 C. glabrata, 20 C. parapsilosis, 8 C. krusei, and 6 other Candida species) were tested by using the National Committee for Clinical Laboratory Standards M27-A2 broth microdilution methods. The in vitro antifungal activities and spectrum of caspofungin and micafungin were compared with those of amphotericin B, fluconazole, and itraconazole. Caspofungin and micafungin exhibited a broad-spectrum activity against Candida species: caspofungin MIC ranged from 0.125 to 1 microg/mL and micafungin MIC from </=0.03 to 1 microg/mL. C. albicans, C. tropicalis and C. glabrata showed high susceptibility to caspofungin (MIC(90), 0.25 to 0.5 microg/mL) and micafungin (MIC(90), </=0.03 microg/mL), whereas C. parapsilosis was less susceptible to both echinocandins (MIC(90), 1 microg/mL). The MIC(50) for caspofungin, micafungin, amphotericin B, fluconazole, and itraconazole were 0.25, </=0.03, 0.5, 1, and 0.125 microg/mL, respectively. Caspofungin MIC(50) of C. glabrata and C. krusei isolates with decreased susceptibility to azoles were 0.25 and 0.5 microg/mL, respectively, and micafungin MIC(50) were </=0.03 and 0.125 microg/mL, respectively. These data showed an excellent in vitro activity of caspofungin and micafungin against clinical strains of Candida species, including isolates with reduced susceptibility to azoles.

Pharmacodynamics of Caspofungin in a Murine Model of Systemic Candidiasis: Importance of Persistence of Caspofungin in Tissues to Understanding Drug Activity

Pharmacokinetic and pharmacodynamic studies were conducted in a murine model of systemic candidiasis to determine the pharmacodynamic parameter linked with caspofungin efficacy. Additional studies defined the importance of persistent tissue drug concentrations to treatment outcome. The pharmacokinetics of caspofungin were determined in the serum and kidneys of infected mice over 96 h. Population pharmacokinetic analysis demonstrated a serum terminal half-life (t(1/2)) for caspofungin of 20.2 h when only serum concentrations were considered, but the terminal t(1/2) increased to 59.2 h when serum and kidney concentration-time data were co-modeled. In dose-range studies, the dose-response effect was well described by an inhibitory sigmoid curve for the exposure-effect killing caused by the drug (r2 > 0.96; P << 0.001). In dose-fractionation studies, fungal counts in kidneys were not statistically different for total doses given as one, two, or four equally divided doses over 96 h, indicating that the area under the concentration-time curve/MIC is the pharmacodynamic parameter that predicts caspofungin efficacy in our infection model. In a separate study, mice infected with Candida albicans 24 h after serum concentrations of caspofungin fell below the MIC for the fungal isolate had significant reductions in fungal densities in their kidneys compared with the growth of fungi in the kidneys of untreated controls (P = 0.005). This in vivo biological assay demonstrates that therapeutic concentrations of caspofungin persist at the site of infection in kidney tissue well after serum concentrations fall below the MIC, underscoring the primacy of caspofungin levels in tissues on determining treatment outcome.

Comparison of the Fungicidal Activities of Caspofungin and Amphotericin B against Candida glabrata

We investigated the fungicidal activity of caspofungin (CAS) and amphotericin B (AMB) against 16 clinical isolates of Candida glabrata. The minimum fungicidal concentrations (MFCs) of CAS were similar to those of AMB, ranging from 2.0 to >8.0 microg/ml. Time-kill assays performed on selected isolates showed that AMB was fungicidal at concentrations four times the MIC while CAS was not. A neutropenic-mouse model of disseminated infection was utilized to determine the residual fungal kidney burden. While doses as low as 0.3 and 1 mg/kg of body weight/day of CAS and AMB, respectively, were effective at reducing the counts with respect to controls, organ sterilization was reached when both drugs were administered at 5 mg/kg/day. Our study reveals that, similar to AMB, CAS has the potential for a fungicidal effect in vivo against this difficult-to-treat fungal pathogen.

Attenuation of the Activity of Caspofungin at High Concentrations against Candida albicans : Possible Role of Cell Wall Integrity and Calcineurin Pathways

Caspofungin had diminished activity in vitro against Candida albicans at concentrations of 8 to 32 microg/ml. This phenomenon was markedly attenuated in a deltamkc1/deltamkc1 deletion mutant and by the addition of cyclosporine to the wild type. Short exposure to these caspofungin concentrations resulted in MKC1 up-regulation, suggesting roles of cell wall integrity and calcineurin pathways.

Comparison of Two Probes for Testing Susceptibilities of Pathogenic Yeasts to Voriconazole, Itraconazole, and Caspofungin by Flow Cytometry

A cytometric approach to determine the susceptibilities of Candida spp. and Cryptococcus neoformans to voriconazole, itraconazole, and caspofungin is described. A total of 63 clinical isolates with different susceptibility patterns were exposed for 1, 2, 4, and 6 h to serial concentrations of each antifungal agent, followed by staining with two fluorescent probes: propidium iodide (PI) and FUN-1. FUN-1 was able to identify the susceptibility patterns of the assayed strains to the three agents after 1 h. PI penetrated a maximum of 50% of the cells treated with PI, at the highest concentration of caspofungin, 16 mug/ml, after 6 h of incubation (this percentage varied with the strain and was drug concentration and time of incubation dependent) and did not stain cells treated with high concentrations of either azole after 6 h. The use of FUN-1 appears to be an excellent fast and reliable alternative to the classical dilution method for determining the susceptibility of Candida spp. and C. neoformans to these three antifungal agents.

Caspofungin Susceptibility Testing of Candida inconspicua : Correlation of Different Methods with the Minimal Fungicidal Concentration

Minimal inhibitory and minimal fungicidal concentrations of caspofungin were determined for 48 Candida inconspicua isolates. By using CLSI (formerly NCCLS) methodology with the partial inhibition endpoint criterion, caspofungin exhibited a good fungicidal effect against C. inconspicua (the MIC(90) was 0.25 microg/ml and the minimum fungicidal concentration [MFC] was 0.5 microg/ml after 24 h). Total inhibition yielded falsely elevated MICs, exceeding even the respective MFCs.

Anti-metabolic activity of caspofungin against Candida albicans and Candida parapsilosis biofilms

Candidiasis can be associated with the formation of biofilms on bioprosthetic surfaces and the intrinsic resistance of Candida albicans biofilms to the most commonly used antifungal agents has been demonstrated. In this study, we report on the antifungal activity of caspofungin at two different concentrations, on C. albicans and Candida parapsilosis biofilms with different ages of maturation. Fifteen strains of C. albicans (10 strains susceptible to fluconazole in vitro and five strains resistant to this antifungal agent) and six strains of C. parapsilosis (all were susceptible to fluconazole in vitro) were studied. The antifungal activity of caspofungin was assessed by looking for a significant inhibition of the metabolic activity of yeasts within biofilms. Biofilms of Candida were produced in vitro, on silicone catheters. Caspofungin used at MIC did not modify the metabolic activity of C. albicans, whatever the maturation age of the biofilms. The same concentration of caspofungin significantly reduced the metabolism (P<or=0.001) of 25% (biofilms of 48 h) to 50% (biofilms of 2 h) of the C. parapsilosis yeasts. The use of a therapeutic concentration of caspofungin (2 mg/L) significantly decreased (P<or=0.001) the metabolism of all the strains of C. albicans and C. parapsilosis tested, independently of the biofilm maturation age. This potent antifungal activity of caspofungin on C. albicans biofilms was observed independently of the yeast susceptibility to fluconazole. This study demonstrated that caspofungin used at MIC was not sufficient to reduce C. albicans biofilms, but it suggested an activity on C. parapsilosis biofilms depending on their maturation age. This study also indicated that caspofungin used at 2 mg/L could be a good candidate in the prevention of candidiasis associated with silicone medical devices. Our results also suggested that fluconazole resistance of yeasts did not affect caspofungin activity.