Antifungal Activity of Antifungal Drugs,as Well as Drug Combinations Against <Emphasis Type="Italic">Exophiala dermatitidis</Emphasis>

To evaluate the in vitro efficacy of common antifungal drugs, as well as the interactions of caspofungin with voriconazole, amphotericin B, or itraconazole against the pathogenic black yeast Exophiala dermatitidis from China, the minimal inhibitory concentrations (MICs) of terbinafine, voriconazole, itraconazole, amphotericin B, fluconazole, and caspofungin against 16 strains of E. dermatitidis were determined by using CLSI broth microdilution method (M38-A2). The minimal fungicidal concentrations (MFCs) were also determined. Additionally, the interactions of caspofungin with voriconazole, amphotericin B, itraconazole or fluconazole, that of terbinafine with itraconazole, or that of fluconazole with amphotericin B were assessed by using the checkerboard technique. The fractional inhibitory concentration index (FICI) was used to categorize drug interactions as following, synergy, FICI ≤ 0.5; indifference, FICI > 0.5 and ≤4.0; or antagonism, FICI > 4.0. The MIC ranges of terbinafine, voriconazole, itraconazole, amphotericin B, fluconazole, and caspofungin against E. dermatitidis were 0.06–0.125 mg/l, 0.25–1.0 mg/l, 1.0–2.0 mg/l, 1.0–2.0 mg/l, 16–64 mg/l, and 32–64 mg/l, respectively. The in vitro interactions of caspofungin with voriconazole, amphotericin B, and itraconazole showed synergic effect against 10/16(62.5%), 15/16(93.75%), and 16/16(100%) isolates, while that of caspofungin with fluconazole showed indifference. Besides, the interaction of terbinafine with itraconazole as well as that of fluconazole with amphotericin B showed indifference. Terbinafine, voriconazole, itraconazole, and amphotericin B have good activity against E. dermatitidis. The combinations of caspofungin with voriconazole, amphotericin B or itraconazole present synergic activity against E. dermatitidis. These results provide the basis for novel options in treating various E. dermatitidis infections.     

Antifungal pharmacodynamic characteristics of amphotericin B against Trichosporon asahii, using time-kill methodology

We determined the MIC of amphotericin B against 45 Trichosporon asahii isolates from various clinical and environmental sources, and used in vitro time-kill methods to characterize the relationship between amphotericin B concentrations and MIC for four representative T. asahii isolates. Amphotericin B had concentration-dependent antifungal activity. MICs ranged from 0.5 to 16 microg/ml, and most T. asahii isolates (76%, 34/45) were inhibited at safely achievable amphotericin B serum concentrations (< or = 2 microg/ml). However, 40% (18/45) of isolates were not killed at these concentrations (MFCs from 1.0 to 32 microg/ml). At concentrations > or = 2 x MIC, amphotericin B exhibited fungicidal activity (< 99.9% reduction in CFU) over a 12-hr time-period; the maximal effect was achieved at > or =4 x MIC. Susceptibility testing confirmed the resistance of T. asahii to amphotericin B, and in vitro pharmacodynamic results also suggest that amphotericin B is not suitable therapy for T. asahii infection.     

In vitro activities of voriconazole, fluconazole, itraconazole and amphotericin B against non Candida albicans yeast isolates

Antifungal susceptibility testing was performed on 197 yeast isolates from the BCCM/IHEM biomedical fungi and yeasts collection (Belgian Co-ordinated Collections of Micro-organisms / IPH-Mycology) to study the in vitro activity of voriconazole against fluconazole, itraconazole and amphotericin B. MICs of the four antifungal agents were determined by an adapted NCCLS M27-A microdilution reference method. MIC readings were visually and spectrophotometrically determined. Optical density data were used for calculation of the MIC endpoints. For amphotericin B, the MIC endpoint was defined as the minimal antifungal concentration that exerts 90% inhibition, compared to the control growth. The azoles endpoints were determined at 50% inhibition of growth. The MIC distribution of voriconazole susceptibilities showed that 193 isolates had a MIC < or = 2 microg/ml and 185 a MIC < or = 1 microg/ml. Cross-tabulation of voriconazole, fluconazole, and itraconazole MICs indicated that voriconazole MICs raised with fluconazole and itraconazole MICs. The in vitro data obtained in this study suggest that voriconazole may also be effective treating yeast infection in patients infected with fluconazole or itraconazole resistant isolates.     

In vitro antifungal susceptibility of clinical isolates of Cryptococcus neoformans var. neoformans and C. neoformans var. gattii

One of the differences observed between the two varieties of Cryptococcus neoformansis the greater difficulty to achieve an adequate therapeutical response in patients affected by C. neoformans var. gattii, an observation that has been validated in vitro only rarely. The aim of this work was to study the susceptibility patterns of 35 Colombian clinical isolates of C. neoformans, 20 of which belonged to the var. neoformans and 15 to the var. gattii. The minimal inhibitory concentration (MIC) was determined by broth microdilution, according to a modification of the methodology proposed by the National Committee for Clinical Laboratory Standards (NCCLS), using the breakpoints recently suggested by Nguyen et al. (Antimicrob Agents Chemother 1998; 42: 471-472). The antifungals tested were amphotericin B, fluconazole and itraconazole. Most of the isolates were susceptible to the three antimycotics tested regardless of the variety. Resistance to amphotericin B (MIC=2 microg/ml) was documented in two (10%) C. neoformans var. neoformans isolates; additionally, five (33%) C. neoformans var. gattii isolates felt in the category of fluconazole susceptible but dose dependent (MIC 16 microg/ml). In general, all C. neoformans var. gattii isolates proved susceptible only to the higher concentrations of the antifungals tested. For amphotericin B, seven (47%) isolates of this variety had MICs of 1 microg/ml, for fluconazole there were seven (47%) with MICs of 8 microg/ml and in the case of itraconazole, 10 isolates (66%) had MICs > 0.03 microg/ml. The data showed that although these isolates would be classified as susceptible, they actually require greater concentrations of the antifungals to be inhibited. This finding may well correlate both with the difficulty to attain therapeutic success in patients affected with C. neoformans var. gattii and with the need for more prolonged treatment courses in such cases.     

The synergism of antifungals and essential oils against Candida spp. evaluated by a modified gradient-diffusion method

The usefulness of modified method of MIC Test Strip, for determining the synergistic effect of essential oils in the liquid or volatile phase with fluconazole and voriconazole, was evaluated. Geranium oil used against C. albicans in agar dilution test, at a concentration of 1/2 MIC caused a drop in the value of fluconazole MIC from 12.0 mg/l to 0.064 mg/l and voriconazole from 0.125 mg/l to 0.006 mg/l. A similar effect of drug combinations with essential oils was obtained in the case of C. glabrata study. Volatile Clove oil and cytronelal, applied in subMIC concentrations, also caused a reduction offluconazole and voriconazole MICs. Thus, utility of this simple methods developed by us for testing the effectiveness of combinations of known drugs and new compounds with antifungal activity, has been confirmed.     

Broth Microdilution and Time–Kill Testing of Caspofungin, Voriconazole, Amphotericin B and their Combinations Against Clinical Isolates of Candida krusei

Treatment of invasive Candida krusei infections can be difficult due to its intrinsic fluconazole resistance and its reduced susceptibility to amphotericin B and flucytosine. Caspofungin (CAS) acts on a different cellular target, and its combination with voriconazole (VOR) or amphotericin B (AmB) appears promising. We evaluated the activity of CAS, VOR and AmB alone and in combination at 1/4, 1, 4xMIC concentrations by time–kill method against 30 C. krusei isolates. All isolates were susceptible to CAS and VOR; AmB MICs were 2 μg/ml for 50% of isolates by broth microdilution. CAS showed a fast killing activity at all concentrations; it was fungistatic at 1/4xMICs and fungicidal at 1-4xMICs in general. VOR displayed a concentration-independent fungistatic activity against all isolates. AmB exhibited a concentration-dependent activity; it was fungistatic at 1/4-1xMIC and fungicidal at 4xMIC. The most common interaction was indifference for both combinations. Frequency of synergic interaction for the VOR + CAS combination was 66.7% at 1/4xMIC after 48 h. The best results for CAS + AmB combination were obtained at 4xMIC in the first 4–8 h; synergic interaction was detected for 20 isolates (66.7%) at 4xMIC after 4 h. Consequently, VOR and CAS alone have been found effective, and high AmB MICs are remarkable against clinical C. krusei isolates in vitro. The combinations of CAS with VOR or AmB have exhibited promising results.     

Comparison between efficacy of allicin and fluconazole against Candida albicans in vitro and in a systemic candidiasis mouse model

The efficacy of allicin compared with fluconazole in alleviating systemic Candida albicans infections was evaluated both in vitro and in vivo through a systemic candidiasis mouse model. Determination of in vitro minimum inhibitory concentrations (MICs) for different C. albicans isolates revealed that both allicin and fluconazole showed different MICs that ranged from 0.05 to 12.5 μg mL(-1) and 0.25 to 16 μg mL(-1) , respectively. A time-kill study showed a significant effect of allicin (P<0.01) against C. albicans, comparable to that of fluconazole. Scanning electron microscopy observation revealed that, similar to fluconazole, allicin produced structural destruction of C. albicans cell surface at low MIC and lysis or puncture at high MIC concentrations. Treatment of BALB/c mice systemically infected with C. albicans showed that although the allicin treatment (at 5 mg kg(-1) day(-1) ) was slightly less efficacious than fluconazole treatment in terms of the fungal load reduction and host survival time, it was still effective against C. albicans in terms of mean survival time, which increased from 8.4 to 15.8 days. These results demonstrate the efficacy of anticandidal effects of allicin both in vitro and in an animal model of candidiasis and affirm the potential of allicin as an adjuvant therapy to fluconazole.     

Comparison of In Vitro and Vivo Efficacy of Caspofungin Against Candida parapsilosis, C. orthopsilosis, C. metapsilosis and C. albicans

Caspofungin activity was determined in vitro and in vivo against three Candida orthopsilosis, three C. metapsilosis, two C. parapsilosis sensu stricto and two C. albicans isolates. MIC values and killing activity were determined in RPMI-1640 plus 50?% human serum. Neutropenic (cyclophosphamide-treated) mice were infected intravenously. Five-day intraperitoneal treatment with caspofungin was started after 24?h postinfection. Kidney burden was analyzed using the Kruskal-Wallis test with Dunn's post-test. In killing studies, caspofungin was fungistatic and fungicidal against C. albicans at ≥0.25 and ≥2?μg/ml concentrations, respectively. Caspofungin was fungistatic at ≥8-16, ≥2-8 and at ≥2-8?μg/ml against C. parapsilosis, C. orthopsilosis and C. metapsilosis, respectively. In the murine model, C. albicans was inhibited by 1, 2 and 5 mg/kg of caspofungin (P?相似文献   

In vitro susceptibility to antifungal agents of environmental Cryptococcus spp. isolated in the city of Ribeirão Preto, São Paulo, Brazil

Infections by Cryptococcus strains other than C. neoformans have been detected in immunocompromised patients. Of these strains, three are considered human pathogens: C. albidus, C. laurenttii, and C. uniguttulatus. This study deals with the in vitro susceptibility of Cryptococcus to drugs such as amphotericin B, itraconazole, fluconazole, and 5-fluorocytosine. Environmental Cryptococcus isolates (50) distributed as follows: C. neoformans var. neoformans (16), C. albidus (17), C. laurentii (14), and C. uniguttulatus (3) were evaluated by the micro and macrodilution techniques, according to EUCAST and NCCLS recommendations, respectively. Considering both methodologies the respective minimal inhibitory concentrations (MIC) were 0.125 and 2 microg/ml for amphotericin B, 0.06 and 8 microg/ml for itraconazole, and 0.5 and more than 64 microg/ml for fluconazole and 5-fluorocytosine. Agreement percentages for the two methodologies were 100% for amphotericin B and fluconazole for all the strains tested. For itraconazole, the agreement percentage was 81.3% in the C. neoformans strain and 100% for all the others. All species had a agreement percentage of 94.1 to 100% when susceptibility to 5-fluorocytosine was tested. It is concluded that environmental isolates of C. neoformans var. neoformans, C. albidus, C. laurentii, and C. uniguttulatus may show high MICs against certain drugs, suggesting in vitro primary resistance to the antifungals tested.     

In vitro activity of amphotericin B and anidulafungin against Candida spp. biofilms

Invasive infections caused by Candida spp. are increasing worldwide and are becoming an important cause of morbidity and mortality in immunocompromised patients. A large number of manifestations of candidiasis are associated with the formation of biofilms on inert or biological surfaces. Candida spp. biofilms are recalcitrant to treatment with conventional antifungal therapies. The aim of this study was dual 1) to determine the prevalence of biofilm producers among clinical isolates from catheter (16 C. albicans ) and blood culture (2 C. albicans and 30 C. tropicalis), and 2) to determine the activity of amphotericin B and anidulafungin against C. albicans and C. tropicalis biofilms of 24 and 48 hours of maturation. Biofilms were developed using a 96-well microtitre plate model and production and activity of antifungal agents against biofilms were determined by the tetrazolium (XTT) reduction assay. Of catheter and blood isolates, 62.5 and 56.25%, respectively, produced biofilms. By species, 68.42% of C. albicans and 53.33% of C. tropicalis were biofilm producers. C. albicans biofilms showed more resistance to amphotericin B and anidulafungin than their planktonic counterparts. Complete killing of biofilms was never achieved, even at the highest concentrations of the drugs tested. Anidulafungin displayed more activity than amphotericin B against C. albicans biofilms of 24 hours of maturation (GM MIC 0.354 vs. 0.686 microg/ml), but against C. tropicalis biofilms amphotericin B was more active (GM MIC 11.285 vs. 0.476 microg/ml). In contrast, against biofilms with 48 hours maturation, amphotericin B was more active against both species.     

氯喹与氟康唑联合对新生隐球菌的体外药敏实验

目的研究氯喹与氟康唑体外联合应用对隐球菌生长作用的影响。方法参考M27-A方案,检测10μmol/L,100μmol/L与1 000μmol/L 3种浓度氯喹与氟康唑联合后对20株菌株的氟康唑对隐球菌最小抑菌浓度与最小杀菌浓度的变化。结果与10μmol/L氯喹组相比,100μmol/L以上浓度的氯喹组可以显著降低氟康唑对隐球菌的M IC与MFC。结论氯喹在体外可以提高氟康唑抗隐球菌的作用,与氟康唑具有协同抗隐球菌的作用。     

Amphotericin B-metronidazole combination against Candida spp

Interaction between amphotericin B and metronidazole was studied against Candida albicans, Candida tropicalis, Candida parapsilosis, Candida krusei, and Candida lusitaniae strains. Minimum inhibitory concentrations (MICs) of the drugs alone and in combination were determined by means of the checkerboard method on YNB supplemented agar. Minimum fungicidal concentrations (MFCs) were determined on Sabouraud dextrose agar. Based on the MIC and MFC values, fractionary indices were determined respectively for inhibitory and lethal activities of the amphotericin B-metronidazole combination. These indices showed occurrence of additive and synergistic interactions between the drugs, but the synergysm was predominant against the studied strains.     

In vitro antifungal activities of anidulafungin and micafungin, licensed agents and the investigational triazole posaconazole as determined by NCCLS methods for 12,052 fungal isolates: review of the literature

The echinocandins anidulafungin and micafungin and the triazole posaconazole are currently undergoing phase III clinical trials. Caspofungin and voriconazole have recently been licensed for the treatment of aspergillosis (both agents), other less common mould (voriconazole) and candidal (caspofungin) infections. This review summarizes the published in vitro data obtained by NCCLS or NCCLS modified methods on the in vitro fungistatic and fungicidal activities of these five agents for yeasts and moulds in comparison to the established agents, amphotericin B, fluconazole, itraconazole, and flucytosine. Among the yeasts, the echinocandins have less activity for Candida parapsilosis and Candida guilliermondii, no activity for Cryptococcus neoformans and Trichosporon spp., but good fungistatic and fungicidal activity in vivo and in vitro for most of the other Candida spp.; this fungicidal activity has been reported by minimum fungicidal concentrations (MFCs) or time kill curve results. The new triazoles exhibit good fungistatic activity (but not fungicidal) for most Candida spp., C. neoformans, and Trichosporon spp. For the Aspergillus spp. evaluated, the echinocandins have similar or better fungistatic activity than those of amphotericin B and the triazoles, but fungicidal activity has been demonstrated only with amphotericin B and the triazoles, with the exception of fluconazole. Most studies showed posaconazole and voriconazole minimum inhibitory concentrations (MICs) ranging from 0.25 to 8 microg/ml for non-solani Fusarium spp., while MIC and minimum effective concentration (MEC) endpoints of the echinocandins were >8 microg/ml. The fungistatic activity of the triazoles is also superior to that of the echinocandins for most of the dimorphic fungi and the Zygomycetes. However, micafungin has activity for the mould phase of most dimorphic fungi, but not for the parasitic or yeast phase of Paracoccidioides brasiliensis. The echinocandins appear to have variable and species dependent fungistatic activity for the dematiaceous fungi, but all agents have poor or no activity against most isolates of Scedosporium prolificans. Only amphotericin B exhibit good fungistatic activity against the Zygomycetes. The combination of caspofungin with some triazoles, amphotericin B or liposomal amphotericin B has been synergistic in vitro, in animal models and in patients. Breakpoints are not available for any mould and antifungal agent combination. In vitro/in vivo correlations should aid in the interpretation of these results, but standard testing conditions are needed for the echinocandins, especially for mould testing, to obtain reliable results.     

Etest for assessing the susceptibility of filamentous fungi

The purpose of this study was to evaluate the Etest as an in vitro antifungal susceptibility test method for different moulds originating from human samples and from the environment. A total of 50 isolates (1 Acremonium, 18 Aspergillus, 2 Cladosporium, 1 Epicoccum, 15 Penicillium, 2 Scopulariopsis and 11 Trichoderma strains) were tested by the Etest. Forty-six of the tested moulds (92%) were resistant to fluconazole with minimal inhibitory concentrations (MICs) > or = 256 microg ml(-1). There were strains resistant to ketoconazole among Aspergillus niger, A. ochraceus and Cladosporium spp. with MICs > 32 microg ml(-1). For fluconazole, no differences were observed using two different inocula, while for itraconazole, ketoconazole and amphotericin B, a 1 or less step 2-fold dilution difference in MIC was seen for the most of 10 selected strains. The MICs of fluconazole and amphotericin B obtained for Trichoderma strains by the Etest and the agar dilution method were also compared. MICs for fluconazole were in agreement, while MICs for amphotericin B were higher with 1 or 2 steps of 2-fold dilutions for most of Trichoderma strains in the case of the agar dilution method.     

Increased resistance to antifungal antibiotics ofCandida spp. adhered to silicone

Summary The minimal inhibitory concentrations (MICs) and minimal fungicidal concentrations (MFCs) of amphotericin B, miconazole, ketoconazole, fluconazole, and itraconazole were determined for non-adhered cells and cells adhered to sections of a silicone urinary catheter. The densities of adhered cells were established with cells radiolabeled with tritiated leucine. Well defined MICs and MFCs were established for amphotericin B for representative adhered strains. In contrast, the azoles, especially fluconazole, did not give clear end points and the MICs and MFCs were arbitrarily determined. MFCs for the adhered cells generally were 2- to 5-fold higher than those of non-adhered cells. Techniques that include adhered-cell susceptibilities may be necessary before antifungal regimens for prosthetic device-associated yeast infections are appropriately defined.This paper is dedicated to Professor Herman Jan Phaff in honor of his 50 years of active research which still continues.     

Determination of antifungal activities in serum samples from mice treated with different antifungal drugs allows detection of an active metabolite of itraconazole

To establish an in vitro method of predicting in vivo efficacy of antifungal drugs against Candida albicans and Aspergillus fumigatus, the antifungal activities of fluconazole, itraconazole, and amphotericin B were determined in mouse serum. The minimum inhibitory concentration (MIC) of each drug was measured using mouse serum as a diluent. For C. albicans, the assay endpoint of azoles was defined as inhibition of mycelial extension (mMIC) and for A. fumigatus, as no growth (MIC). The MICs of amphotericin B for both pathogens were defined as the MIC at which no mycelial growth occurred. Serum MIC or mMIC determinations were then used to estimate the concentration of the drugs in serum of mice treated with antifungal drugs by multiplying the antifungal titer of the serum samples by the serum (m)MIC. The serum drug concentrations were also determined by HPLC. The serum concentrations estimated microbiologically showed good agreement with those determined by HPLC, except for itraconazole. Analysis of the serum samples from itraconazole-treated mice by a sensitive bioautography revealed the presence of additional spots, not seen in control samples of itraconazole. The bioautography assay demonstrated that the additional material detected in serum from mice treated with itraconazole was an active metabolite of itraconazole. The data showed that the apparent reduction in the itraconazole serum concentration as determined by HPLC was the result of the formation of an active metabolite, and that the use of a microbiological method to measure serum concentrations of drugs can provide a method for prediction of in vivo efficacy of antifungal drugs.     

The presence of fluconazole-resistant Candida dubliniensis strains among Candida albicans isolates from immunocompromised or otherwise debilitated HIV-negative Turkish patients

The newly described species Candida dubliniensis phenotipically resembles Candida albicans in many respects and so it could be easily misidentified. The present study aimed at determining the frequency at which this new Candida species was not recognized in the authors' university hospital clinical laboratory and to assess antifungal susceptibility. In this study, six identification methods based on significant phenotypic characteristics each proposed as reliable tests applicable in mycology laboratories for the differentiation of the two species were performed together to assess the clinical strains that were initially identified as C. albicans. Only the isolates which have had the parallel results in all methods were assessed as C. dubliniensis. One hundred and twenty-nine C. albicans strains isolated from deep mycosis suspected patients were further examined. Three of 129 C. albicans (2 from oral cavity, 1 from sputum) were reidentified as C. dubliniensis. One of the strains isolated from oral cavity and that from the sputum were obtained at two months intervals from the same patient with acute myeloid leukemia, while the other oral cavity strain was obtained from a patient who had previously been irradiated for a laryngeal malignancy. Isolates were all susceptible in vitro to amphotericin B, with the MIC range 0.125 to 0.5 &mgr;g/ml, resistant to fluconazole, with MICs >/=64 &mgr;g/ml, and resistant to ketoconazole, with MICs >/=16 &mgr;g/ml, dose-dependent to itraconazole with a MIC range 0.25-0.5 &mgr;g/ml, and susceptible to flucytosine, with a MIC range 1-4 &mgr;g/ml.     

In vitro antifungal activities of voriconazole and reference agents as determined by NCCLS methods: Review of the literature

Voriconazole (Vfend™) is a new triazole that currently is undergoing phase III clinical trials. This review summarizes the published data obtained by NCCLS methods on the in vitro antifungal activity of voriconazole in comparison to itraconazole, amphotericin B, fluconazole, ketoconazole and flucytosine. Voriconazole had fungistatic activity against most yeasts and yeastlike species (minimum inhibitory concentrations [MICs] <2 μg/ml) that was similar or superior to those of fluconazole, amphotericin B, and itraconazole. Against Candida glabrata and C. krusei, voriconazole MIC ranges were 0.03 to 8 and 0.01 to >4 μg/ml, respectively. For four of the six Aspergillus spp. evaluated, voriconazole MICs (< 0.03 to 2 μg/ml) were lower than amphotericin B (0.25 to 4 μg/ml) and similar to itraconazole MICs. Voriconazole fungistatic activity against Fusarium spp. has been variable. Against F. oxysporum and solani, most studies showed MICs ranging from 0.25 to 8 μg/ml. Voriconazole had excellent fungistatic activity against five of the six species of dimorphic fungi evaluated (MIC₉₀s < 1.0 μg/ml). The exception was Sporothrix schenckii (MIC₉₀s and geometric mean MICs ≥ 8 μg/ml). Only amphotericin B had good fungistatic activity against the Zygomycetes species (voriconazole MICs ranged from 2 to >32 μg/ml). Voriconazole showed excellent in vitro activity (MICs < 0.03 to 1.0 μg/ml) against most of the 50 species of dematiaceous fungi tested, but the activity of all the agents was poor against most isolates of Scedosporium prolificans and Phaeoacremonium parasiticum (Phialophora parasitica). Voriconazole had fungicidal activity against most Aspergillus spp., B. dermatitidis, and some dematiaceous fungi. In vitro/in vivo correlations should aid in the interpretation of these results. This revised version was published online in June 2006 with corrections to the Cover Date.     

Antifungal susceptibility of bloodstream yeasts isolated at a public children's hospital in Brazil: comparison of the Etest and the AFST-EUCAST microdilution method

This study compared the minimum inhibitory concentration (MIC) results from the proposed standard methods of the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antibiotic Susceptibility Testing (AFST-EUCAST) with the commercial system Etest(R) in the evaluation of susceptibility to flucytosine, fluconazole, itraconazole, voriconazole, and amphotericin B of 136 Candida spp. isolated from the blood of hospitalized children. The results presented a greater agreement among Etest(R) MICs +/-2 log2 dilutions of AFST-EUCAST for fluconazole (98.1% and 96.3%) and voriconazole (100% and 100%) for Candida albicans and Candida parapsilosis. For Candida glabrata, the agreement was greater only for fluconazole (81.8%) and voriconazole (100%). For amphotericin B, the agreement between the methods was low for all species. The agreement percentage among the Etest(R) and AFST-EUCAST susceptibility profiles was high according to the MIC breakpoints recommended by the M27-A2 protocol for the majority of the yeasts, except for fluconazole and itraconazole against Candida tropicalis and for itraconazole against C. glabrata and Candida krusei. According to both methodologies, a great number of Candida spp. isolates showed an in vitro susceptibility to all evaluated antifungal agents. Overall, both procedures can be reliable techniques for susceptibility tests of yeasts, but the assessment of interlaboratory agreement and correlation of MICs by different methods with in vivo response are of great importance.     

Evaluation of antifungal pharmacodynamic characteristics of AmBisome against Candida albicans

A liposomal formulation of Amphotericin B (AmBisome), with small unilamellar vesicles containing amphotericin B, shows characteristic pharmacokinetics as liposomes, and in consequence, has different pharmacological activity and toxicity from amphotericin B deoxycholate (Fungizone). In this study, we evaluated the antifungal pharmacodynamic characteristics of AmBisome against Candida albicans using the in vitro time-kill method and murine systemic infection model. A time-kill study indicated that the in vitro fungicidal activities of AmBisome and Fungizone against C. albicans ATCC 90029 increased with increasing drug concentration. For in vivo experiments, leucopenic mice were infected intravenously with the isolate 4 hr prior to the start of therapy. The infected mice were treated for 24 hr with twelve dosing regimens of AmBisome administered at 8-, 12-, 24-hr dosing intervals. Correlation analysis between the fungal burden in the kidney after 24 hr of therapy and each pharmacokinetic/pharmacodynamic parameter showed that the peak level/MIC ratio was the best predictive parameter of the in vivo outcome of AmBisome. These results suggest that AmBisome, as well as Fungizone, has concentration-dependent antifungal activity. Furthermore, since AmBisome can safely achieve higher concentrations in serum than Fungizone, AmBisome is thought to have superior potency to Fungizone against fungal infections.