Susceptibility testing of voriconazole, fluconazole, itraconazole and amphotericin B against yeast isolates in a Turkish University Hospital and effect of time of reading

Synthesis, antimicrobial activity, structure-activity relationship and cytotoxic studies of a new series of functionalized (Z)-3-(2-oxo-2-substituted ethylidene)-3,4-dihydro-2H-benzo[b][1,4]oxazin-2-ones

A new series of functionalized (Z)-3-(2-oxo-2-substituted ethylidene)-3,4-dihydro-2H-benzo[b][1,4]oxazin-2-ones 23-26, incorporating pharmaceutically privileged substructures such as cyclopropyl, naphthyl, biphenyl and cyclohexylphenyl were synthesized in excellent yields. All the synthesized compounds were screened for their in vitro antibacterial activity against gram-(+)ve and gram-(-)ve bacterial species i.e. S. griseus, S. aureus, B. subtillis and E. coli as well as in vitro antifungal activity against fungal species i.e. F. oxysporium, A. niger, P. funiculosum and T. reesei, respectively. In this study, compounds containing cyclopropyl and cyclohexylphenyl substructures were identified as promising antimicrobial agents than standard drugs, ampicillin and chloramphenicol as well as ketoconazole. SAR study illustrates that electron-withdrawing groups increases the antibacterial as well as antifungal activity of 2-oxo-benzo[1,4]oxazines and vice versa. Compounds 23e and 26e, the most active compounds of the series, displayed promising antibacterial activity than Ampicillin and Chloramphenicol. Moreover, compound 26d showed promising antifungal potency as compared to Ketoconazole. Cytotoxic studies of the active compounds i.e. 23c-e, 24e, 25d and 26d-e found to be non-toxic in nature in 3T₃ fibroblast cell lines using MTT assay.

Voriconazole

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Multidrug-resistant Trichosporon: an unusual fungal sepsis in preterm neonates

We report a cluster of three extremely-low birth weight (ELBW), preterm neonates who developed late-onset sepsis (LOS) by Trichosporon asahii within a span of 1 week period. Two of these cases had the initial diagnosis of respiratory distress syndrome and the third one was admitted for low birth weight and prematurity. Initial sepsis screen was negative and blood culture was sterile in all. Late-onset sepsis was developed after the first week of life and the presenting features were lethargy, feeding intolerance, bleeding manifestations, positive sepsis screen and severe thrombocytopaenia. The isolates were sensitive to voriconazole but resistant to both amphotericin-B and fluconazole on all occasions. All the infants were treated with liposomal amphotericin-B before the availability of culture reports but the clinical deterioration was rapid and all three neonates succumbed to death before we could procure voriconazole. The source of the outbreak could not be identified from multiple surface cultures from the unit and screening of the health care staffs. We emphasise the need for high index of suspicion for unusual fungal pathogens, resistant to conventional antifungal drugs while treating preterm neonates with LOS.

Current knowledge of Trichosporon spp. and Trichosporonosis

Trichosporon spp. are basidiomycetous yeast-like fungi found widely in nature. Clinical isolates are generally related to superficial infections. However, this fungus has been recognized as an opportunistic agent of invasive infections, mostly in cancer patients and those exposed to invasive medical procedures. It is possible that the ability of Trichosporon strains to form biofilms on implanted devices, the presence of glucuronoxylomannan in their cell walls, and the ability to produce proteases and lipases are all factors likely related to the virulence of this genus and therefore may account for the progress of invasive trichosporonosis. Disseminated trichosporonosis has been increasingly reported worldwide and represents a challenge for both diagnosis and species identification. Phenotypic identification methods are useful for Trichosporon sp. screening, but only molecular methods, such as IGS region sequencing, allow the complete identification of Trichosporon isolates at the species level. Methods for the diagnosis of invasive trichosporonosis include PCR-based methods, Luminex xMAP technology, and, more recently, proteomics. Treating patients with trichosporonosis remains a challenge because of limited data on the in vitro and in vivo activities of antifungal drugs against clinically relevant species of the genus. Despite the mentioned limitations, the use of antifungal regimens containing triazoles appears to be the best therapeutic approach.

Susceptibilities to amphotericin B, fluconazole and voriconazole of Trichosporon clinical isolates

A total of 35 Trichosporon isolates were collected from the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) project from 1999 to 2006, and their identifications as well as drug susceptibilities were determined. The most frequently isolated species was T. asahii (62.9%), and the most common clinical sample that yielded Trichosporon isolates was urine (37.1%). The etiology of all seven invasive trichosporonosis was T. asahii. For the 22 T. asahii isolates, the MIC(50) and MIC(90) for amphotericin B were 0.25 and 1 μg/mL, respectively. Those for fluconazole were 2 and 4 μg/mL, respectively, and for voriconazole 0.031 and 0.063 μg/mL, respectively. When the intraclass correlation coefficients (ICCs) and agreements were calculated, we found that the MICs of fluconazole obtained from different methods were similar and the inter-method discrepancies were low. Nevertheless, no unanimous MIC of amphotericin B and voriconazole was obtained among different methods.

Voriconazole in the management of nosocomial invasive fungal infections

Voriconazole is a new triazole developed for the treatment of life-threatening fungal infections. The drug is available for both oral and intravenous administration; the oral formulation has excellent bioavailability. The side-effect profile of voriconazole presents an acceptable safety and tolerability spectrum: transient visual disturbances, liver enzyme abnormalities, and skin rashes are the most frequently reported side effects but rarely lead to discontinuation. The potential for drug–drug interactions is high, because of its extensive hepatic metabolism. Careful attention to dosage is required, and serum levels and the effects of interacting drugs should be monitored. Review of 25 470 isolates of yeasts and 3216 isolates of filamentous fungi showed voriconazole to have broad-spectrum activity against pathogenic yeasts including intrinsically fluconazole-resistant isolates such as Candida krusei, dimorphic fungi, and opportunistic moulds like Aspergillus spp, amphotericin-B-resistant Aspergillus terreus, Fusarium spp, and Scedosporium apiospermum. It displays excellent clinical efficacy in patients with fluconazole-resistant and -susceptible Candida infections, invasive bone and central nervous system aspergillosis, and various refractory fungal infections. Voriconazole has been approved by the US Food and Drug Administration and by the European Medicines Agency for the treatment of invasive aspergillosis, serious infections caused by Fusarium and S. apiospermum, fluconazole-resistant invasive Candida infections, and candidemia in nonneutropenic patients.

Antifungal susceptibility profile of Trichosporon isolates: correlation between CLSI and etest methodologies

The aim of the present study was to evaluate the antifungal susceptibility profile of Trichosporon species isolated from different sources employing the Clinical and Laboratory Standards Institute (CLSI) method and E-test method. Thirty-four isolates of Trichosporon spp. and six CBS reference samples were tested for their susceptibility to Amphotericin B, 5-flucytosine, Fluconazole, Itraconazole, Voriconazole and Terbinafine. All species showed high Minimun Inhibitory Concentrations (MIC) for Itraconazole and susceptibility to Fluconazole, The comparison among the results obtained by the CLSI method and E-test revealed larger discrepancies among 5-flucytosine and Itraconazole. The present work provides epidemiological data that could influence therapeutic choices. Furthermore, the comparison between different methodologies could help to analyze results obtained by different laboratories.

Ru(II) complexes of N4 and N2O2 macrocyclic Schiff base ligands: their antibacterial and antifungal studies

Reactions of [RuCl2(DMSO)4] with some of the biologically active macrocyclic Schiff base ligands containing N4 and N2O2 donor group yielded a number of stable complexes, effecting complete displacement of DMSO groups from the complex. The interaction of tetradentate ligand with [RuCl2(DMSO)4] gave neutral complexes of the type [RuCl2(L)] [where L=tetradentate macrocyclic ligand]. These complexes were characterized by elemental, IR, 1H, 13C NMR, mass, electronic, thermal, molar conductance and magnetic susceptibility measurements. An octahedral geometry has been proposed for all complexes. All the macrocycles and macrocyclic Ru(II) complexes along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve (Bacillus subtilis, Staphylococcus aureus) and Gram -ve (Escherichia coli, Klebsiella pneumonia) bacteria. All these compounds were found to be more active when compared to streptomycin and ampicillin. The representative macrocyclic Schiff bases and their complexes were also tested in vitro to evaluate their activity against fungi, namely, Aspergillus flavus and Fusarium species.

Bloodstream infections due to Trichosporon spp.: species distribution, Trichosporon asahii genotypes determined on the basis of ribosomal DNA intergenic spacer 1 sequencing, and antifungal susceptibility testing

The reevaluation of the genus Trichosporon has led to the replacement of the old taxon Trichosporon beigelii by six new species. Sequencing of the ribosomal DNA (rDNA) intergenic spacer 1 (IGS1) is currently mandatory for accurate Trichosporon identification, but it is not usually performed in routine laboratories. Here we describe Trichosporon species distribution and prevalence of Trichosporon asahii genotypes based on rDNA IGS1 sequencing as well as antifungal susceptibility profiles of 22 isolates recovered from blood cultures. The clinical isolates were identified as follows: 15 T. asahii isolates, five Trichosporon asteroides isolates, one Trichosporon coremiiforme isolate, and one Trichosporon dermatis isolate. We found a great diversity of different species causing trichosporonemia, including a high frequency of isolation of T. asteroides from blood cultures that is lower than that of T. asahii only. Regarding T. asahii genotyping, we found that the majority of our isolates belonged to genotype 1 (86.7%). We report the first T. asahii isolate belonging to genotype 4 in South America. Almost 50% of all T. asahii isolates exhibited amphotericin B MICs of >or=2 microg/ml. Caspofungin MICs obtained for all the Trichosporon sp. isolates tested were consistently high (MICs >or= 2 microg/ml). Most isolates (87%) had high MICs for 5-flucytosine, but all of them were susceptible to triazoles, markedly to voriconazole (all MICs <or= 0.06 microg/ml).

Genetic diversity and antifungal susceptibility testing of Trichosporon asahii isolated of Intensive Care Units patients

Trichosporon asahii is an opportunistic pathogen, associated with a high mortality rate in immunocompromised patients. In this study, ten isolates, recovered from oral cavity and urine of patients in Intensive Care Units (ICU) over six months, were identified by classical and molecular methods, typed by RAPD and tested in vitro for susceptibility to fluconazole, itraconazole, 5-flucytosine and amphotericin B. A total agreement between the identification of Trichosporon sp by PCR based on sequences of the Internal Transcribed Spacer Regions (ITS) and on the sequences of small-subunit (SSU) ribosomal DNA (rDNA) was found. Randomly amplified of polymorphic DNA (RAPD), with primers P6 and M13, was used to determine the genomic profiles. The dendogram analysis indicated that almost all strains showed similarity >0.9 among them and all strains were multidrug-resistant. This study brings new results on the identification and genotyping of T. asahii isolated from Brazilian ICU patients and information about their antifungal drugs susceptibility.

Paradoxical growth effects of the echinocandins caspofungin and micafungin, but not of anidulafungin, on clinical isolates of Candida albicans and C. dubliniensis

OBJECTIVES

To analyze the effects of a high concentration of three antifungal substances, the echinocandins anidulafungin, caspofungin, and micafungin, on the growth of Candida spp.

METHODS

The growth of 127 C. dubliniensis isolates and 103 C. albicans isolates cultured in medium containing anidulafungin, caspofungin, or micafungin was analyzed using a broth microdilution test according to the guidelines of the CLSI M27-A2 [NCCLS (1997), Wayne, PA]. The final concentrations of all three echinocandins ranged from 0.125 to 64 microg/L.

RESULTS

The different effects of these three antifungal substances on C. albicans cells in comparison to C. dubliniensis cells were quite distinct. When both Candida species were grown in the presence of anidulafungin only a trailing effect was observed. Micafungin induced an Eagle effect in C. dubliniensis only (63%), while caspofungin induced this effect in the majority of C. dubliniensis isolates (90%) and in only a few C. albicans isolates (14%).

CONCLUSIONS

Based on our observations, anidulafungin has effects that are different from the ones produced by micafungin and caspofungin. Whether this different response to high concentrations of echinocandins is based on genetic or phenotypic differences between C. albicans and C. dubliniensis has to be determined in future experiments.

Synthesis, spectral studies and antibacterial activity of novel macrocyclic Co(II) compounds

Ten novel macrocyclic Co(II) compounds have been synthesized by treating four N(4) and six N(2)O(2) donor macrocycles with cobalt chloride in methanol. These compounds were characterized by elemental, IR, (1)H, (13)C NMR, mass, electronic spectral analysis, molar conductance and magnetic susceptibility measurements. Thermal behavior of these compounds has been studied by the thermogravimetric analysis. An octahedral geometry has been proposed for all of these complexes. All the macrocycles and macrocyclic Co(II) compounds along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve and Gram -ve bacteria. All these compounds were found to be more active when compared to streptomycin and ampicillin.

Identification of Candida species isolated from patients in intensive care unit and in vitro susceptibility to fluconazole for a 3-year period

Species level identification of Candida and antifungal susceptibility testing is not generally performed in routine laboratory practice. There is limited information about the distribution of Candida species and antifungal susceptibility in Turkey. In this study, we aimed at identifying Candida isolates to species level from various samples obtained from patients treated in an intensive care unit between 2002 and 2005 and to evaluate fluconazole susceptibilities of the isolates. A total of 320 Candida isolates obtained from 270 patients were identified by conventional methods and using API (Candida and/or 20C AUX) system. Antifungal susceptibility testing was performed by broth microdilution method. Candida albicans was isolated with the highest frequency (65.6%) followed by C. parapsilosis (11.3%), C. glabrata (8.8%) and C. tropicalis (7.8%). Of all the isolates, 92.9% revealed susceptibility to fluconazole. Susceptibility to fluconazole was highest for C. albicans followed by C. parapsilosis and C. glabrata. The MIC(90) values for C. albicans, C. parapsilosis, C. glabrata and C. tropicalis were 1, 2, 8 and 4 mug ml(-1) respectively. Fluconazole remains effective against both C. albicans and the majority of non-albicans Candida species. In this study, we determine the distribution of Candida species and evaluate the susceptibilities of the isolates, particularly for the azoles.

Efficacy of voriconazole in a guinea pig model of invasive trichosporonosis

We have evaluated the efficacy of voriconazole (VRC) in a systemic infection by Trichosporon asahii in immunosuppressed guinea pigs. VRC was more effective than amphotericin B in prolonging survival and reducing tissue burden. The best results were obtained with VRC at 10 mg/kg of body weight/day.

Evaluation of concentration of voriconazole in aqueous humor after topical and oral administration in horses

OBJECTIVE

To determine penetration of topically and orally administered voriconazole into ocular tissues and evaluate concentrations of the drug in blood and signs of toxicosis after topical application in horses.

ANIMALS

11 healthy adult horses.

PROCEDURE

Each eye in 6 horses was treated with a single concentration (0.5%, 1.0%, or 3.0%) of a topically administered voriconazole solution every 4 hours for 7 doses. Anterior chamber paracentesis was performed and plasma samples were collected after application of the final dose. Voriconazole concentrations in aqueous humor (AH) and plasma were measured via high-performance liquid chromatography. Five horses received a single orally administered dose of voriconazole (4 mg/kg); anterior chamber paracentesis was performed, and voriconazole concentrations in AH were measured.

RESULTS

Mean +/- SD voriconazole concentrations in AH after topical administration of 0.5%, 1.0%, and 3.0% solutions (n = 4 eyes for each concentration) were 1.43 +/- 0.37 microg/mL, 2.35 +/- 0.78 microg/mL, and 2.40 +/- 0.29 microg/mL, respectively. The 1.0% and 3.0% solutions resulted in significantly higher AH concentrations than the 0.5% solution, and only the 3.0% solution induced signs of ocular toxicosis. Voriconazole was detected in the plasma for 1 hour after the final topically administered dose of all solutions. Mean +/- SD voriconazole concentration in AH after a single orally administered dose was 0.86 +/- 0.22 microg/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that voriconazole effectively penetrated the cornea in clinically normal eyes and reached detectable concentrations in the AH after topical administration. The drug also penetrated noninflamed equine eyes after oral administration. Low plasma concentrations of voriconazole were detected after topical administration.

Evaluation of the microdilution, Etest and disk diffusion methods for antifungal susceptibility testing of clinical strains of Trichosporon spp

Trichosporon spp are well recognized as pathogens capable of causing invasive disease. Despite the increasing frequency and severity of trichosporonosis, data on the antifungal susceptibility of Trichosporon spp. are limited and recommendations for in vitro testing of this fungus are not included in the guidelines of the National Committee for Clinical Laboratory Standards. The purpose of this study was to determine the in vitro susceptibility of clinical Trichosporon isolates to systemic antifungals. We evaluated the in vitro activity of amphotericin B, fluconazole, itraconazole and voriconazole against 27 clinical isolates of Trichosporon spp. (14 T. mucoides and 13 T. asahii) using NCCLS M27-A2 reference microdilution, Etest and disk diffusion methods. In the microdilution and Etest methods Trichosporon spp. demonstrated relatively high minimum inhibitory concentrations (MICs) for fluconazole (MIC90 4 and 6 microg/ml, respectively) and relatively low MICs for voriconazole (MIC90 0.125 and 0.125 microg/ml, respectively). MICs for amphotericin B determined on antibiotic medium 3 were lower (MIC90 0.06 microg/ml) than those on RPMI (MIC90 1 microg/ml). Observed agreements were 81-100% according to these drugs. Disk diffusion zone diameters correlate inversely with MICs from dilution tests except for amphotericin B. Validation of the clinical significance of these observations demands determination of MIC breakpoints for Trichosporon and in vitro- in vivo correlation studies.

Microbiological Characteristics of Medically Important Trichosporon Species

Trichosporon species are opportunistic pathogens associated with a high mortality rate in immunocompromised patients. Disseminated trichosporonosis is uncommon but reports are increasing. In this study, using 16 stock clinical isolates of suspected Trichosporon species and 4 known Trichosporon strains, we investigated the morphology, physio-biochemistry, molecular biology and antifungal susceptibility characteristics of these Trichosporon spp. and discovered that ITS sequence-based identification is a rapid and accurate identification alternative to most phenotypic or physio- biochemical methods. In vitro antifungal susceptibility tests showed high amphotericin B, itraconazole and terbinafine MIC value in these Trichosporon strains.

In vitro activity of caspofungin compared to amphotericin B, fluconazole, and itraconazole against Candida strains isolated in a Turkish University Hospital

We investigated the in vitro activity of caspofungin compared to amphotericin B, fluconazole, and itraconazole against clinical strains of Candida spp. (n =239). Antifungal susceptibility tests were done in accordance with NCCLS M27-A2 microdilution method and the results were read after 24 and 48 h. In general, 24 h MIC readings were similar to those at 48 h for most isolates and all antifungal agents. Caspofungin was active against all species tested. Caspofungin MICs of Candida parapsilosis were slightly higher than those for other Candida spp. Caspofungin MIC (microg/ml) ranges at 24 h for C. albicans, C. glabrata, C tropicalis, C. parapsilosis, C kefyr, C krusei, C. lusitaniae, C. norvegensis, C. guilliermondii and C. lipolytica were 0.06-2, 0.125-2, 0.125-2, 1-4, 0.125-2, 1-2, 0.5-2, 0.5-1, 0.5-2 and 1-2, respectively. Eagle (paradoxical) effect was observed in 31 and 8% of the isolates at highest concentrations of caspofungin and itraconazole, respectively. The activity of caspofungin against fluconazole- and/or itraconazole-resistant isolates was similar to that detected for the susceptible ones. We conclude that caspofungin appears as a promising antifungal agent with enhanced activity against Candida, including the azole-resistant strains.

A comparative study of fungicidal activities of voriconazole and amphotericin B against hyphae of Aspergillus fumigatus

OBJECTIVES

To study the in vitro fungicidal activity of voriconazole against hyphae of Aspergillus fumigatus and compare the results with those obtained for the known fungicidal drug amphotericin B.

METHODS

A. fumigatus mycelia were grown on Sabouraud dextrose agar and in peptone yeast extract glucose broth until the cultures reached a mid-logarithmic growth phase. The fungicidal activities of voriconazole and amphotericin B against actively growing hyphae of A. fumigatus were examined by a kill-curve experiment and a fungal cell viability test. For the kill-curve study, the drug-treated hyphae were washed, homogenized and resuspended in 1 mL of sterile water, diluted 10-1000 fold and aliquots of 0.1 mL were spread on Sabouraud dextrose agar and allowed to grow for 48 h at 35 degrees C. The cfu were determined and plotted against drug concentrations for each time of exposure to obtain the kill curve. The viability of drug-treated A. fumigatus hyphae was determined by their ability to reduce tetrazolium compound 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide.

RESULTS

Exposure of A. fumigatus hyphae to several concentrations (1-16 mg/L) of voriconazole or amphotericin B for various time intervals killed the hyphae in a time- and drug concentration-dependent manner. Voriconazole at 1 mg/L killed >95% of the hyphae grown on Sabouraud dextrose agar after 48 h of exposure, whereas amphotericin B at the same concentration killed approximately 70% of the hyphae after exposure for the same duration. Approximately 99% killing of hyphae grown in peptone yeast extract glucose broth was obtained for voriconazole at 1 mg/L after 48 h of exposure, whereas amphotericin B at 1 mg/L yielded approximately 82% killing after 48 h. The fungal cell viability test by tetrazolium reduction assay showed that mycelia exposed to > or =1 mg/L (Sabouraud dextrose agar blocks) and > or =2 mg/L (broth cultures) of voriconazole for 48 h completely failed to reduce 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide. At low concentrations (1-2 mg/L) amphotericin B had no detectable effect on 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide reduction by drug-treated mycelia, whereas mycelia treated with 16 mg/L for 48 h showed approximately 50% inhibition of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide reduction compared with the control.

CONCLUSIONS

Voriconazole possesses excellent fungicidal activity against actively growing hyphae of A. fumigatus. A comparison of results with those obtained for the known fungicidal drug amphotericin B shows that, in peptone yeast extract glucose broth, voriconazole has superior fungicidal activity against A. fumigatus hyphae compared with that of amphotericin B.

New agents for the treatment of systemic fungal infections – current status

Systemic antifungal chemotherapy is enjoying its most dynamic era. More antifungal agents are under development than ever before, including agents in entirely new classes. Major goals of current investigations are to identify compounds with a wide spectrum of activity, minimal toxicity and a high degree of target specificity. The antifungal drugs in development include new azoles {voriconazole, posaconazole (formerly SCH-56592), ravuconazole (formerly BMS-207147)}, lipid formulations of amphotericin B, a lipid formulation of nystatin, echinocandins {anidulafungin (formerly, LY-303366, VER-002), caspofungin (formerly MK-991), micafungin (formerly FK-463)}, antifungal peptides other than echinocandins, and sordarin derivatives. This discussion reviews the currently available antifungal agents and summarises the developmental issues that surround these new systemic antifungal drugs.

[In vitro activity of voriconazole and three other antifungal agents against dermatophytes]

INTRODUCTION

The increase in infections due to dermatophytes in recent years led us to study the effectiveness of new antifungal formulations against these microorganisms.

METHODS

The in vitro activity of a new antifungal agent, voriconazole, was compared with three other antifungal agents, itraconazole, fluconazole and terbinafine, against 120 dermatophytes belonging to four species (61 Trichophyton mentagrophytes, 34 Microsporum canis, 13 M. gypseum and 12 T. rubrum). A broth microdilution method was used following the recommendations of the NCCLS document M38-P with some modifications.

RESULTS

Terbinafine was the most active agent against the dermatophytes studied (MIC90 < or = 0.03 mg/ml), followed by voriconazole (MIC90, 0.25 micro g/ml) and itraconazole (MIC90, 0.5 micro g/ml). Fluconazole was the least active antifungal agent. The most susceptible species was M. canis.

CONCLUSIONS

Voriconazole was found to have effective activity against dermatophytes.

Comparison of Etest with modified broth microdilution method for testing susceptibility of Aspergillus spp. to voriconazole

We compared the Etest with a broth microdilution method, performed according to a modified National Committee for Clinical Laboratory Standards guideline (M38-A), for determining the in vitro susceptibility of 77 isolates of Aspergillus spp. (26 A. fumigatus, 21 A. flavus, 10 A. terreus, 9 A. niger, 5 A. nidulellus, 4 A. glaucus, and 2 A. flavipes isolates). Overall, there was 92.2% agreement between both methods when Etest MICs were read at 24 h and 83.1% agreement when both methods were read at 48 h. When Etest MICs were read at 24 h, the agreement was >90% for all species tested except for A. fumigatus (84.6%). When Etest MICs were read at 48 h, the agreement ranged from 50 to 100%. The poorest agreement was seen with A. glaucus (50%) and A. fumigatus (65%). Where a discrepancy was observed between Etest and the reference method, the Etest MIC was generally higher. The Etest appears to be a suitable alternative procedure for testing the susceptibility of Aspergillus spp. to voriconazole.

Susceptibility testing of fungi--current status and open questions

The increase of fungal infections and the improvement of therapeutical options demand reliable antifungal susceptibility testing. In vitro susceptibility testing of fungi--in contrast to bacteria--is not yet established as a routine method. The NCCIS (National Committee for Clinical Laboratory Standards) guidelines for susceptibility testing of yeasts (and proposed for hyphomycetes) are most important for standardization. Meanwhile, essential parts of this test procedure are accepted, but it should still be improved. The concept of using only one test medium for all drugs and test organisms is not realized so far. There are also some test situations that prevent the NCCLS standard from being applied. Based on our experience, this article describes the NCCLS methods and their modifications. It places emphasis on lipophilic drugs showing controversies despite standardization. Furthermore, the prediction of MICs on the clinical outcome is discussed. Since there are some pitfalls in testing antifungals, this should be done in experienced laboratories only. The MIC has to be regarded as only one, but an important, factor in the management of fungal diseases. Host-, drug-, and pathogen-specific data should be considered simultaneously.

Newer antifungal therapy for emerging fungal pathogens

As the number of immunocompromised patients increases, there is a concomitant increase in the number and diversity of fungal infections. Fungi that were once considered harmless or contaminants are now pathogenic in the immunocompromised host. Often these emerging pathogens are indistinguishable from the more familiar fungal infections; however, they are generally more recalcitrant to conventional antifungal therapies. With the antifungal armamentarium now expanding, the clinician now has many more options for these difficult-to-treat mycoses. We review many of the newer antifungal agents (second-generation triazoles, echinocandins, etc.) as therapeutic options for the recently emerging fungal pathogens.

In vitro activity of voriconazole, itraconazole, caspofungin, anidulafungin (VER002, LY303366) and amphotericin B against aspergillus spp

Voriconazole, anidulafungin (VER002, LY303366) and caspofungin are promising antifungal agents which provide a good protection against a variety of fungi, including yeasts and filamentous fungi. In this study, we tested the in vitro efficacy of voriconazole, itraconazole, caspofungin, anidulafungin (VER002, LY303366) and amphotericin B, against different species of Aspergillus spp. isolated from clinical specimens, using a microdilution broth method and following the NCCLS guidelines (document M38-P). We also evaluated the effect that time readings have on MIC results. For caspofungin, we determined the minimun effective concentration (MEC), defined like the lowest concentration of caspofungin causing abnormal hyphal growth. Anidulafungin (VER002, LY303366) was the most active antifungal agent tested with MIC(90) of < or =0,03 mg/L. The activity of voriconazole, and itraconazole very similar with MIC(90) of 0,12 mg/L, 0,12 mg/L respectively. For caspofungin the MEC(90) was of 0,25 mg/L. Amphotericin B was the lest active antifungal agent studied with MIC(90) of 1 mg/L. There were no differences between MIC values at 48 and 72 h. These data demonstrate promising activity of voriconazole, anidulafungin (VER002, LY303366) and caspofungin against Apergillus spp.

Comparison of NCCLS microdilution method and Etest in antifungal susceptibility testing of clinical Trichosporon asahii isolates

We investigated the in vitro activity of amphotericin B, fluconazole, and itraconazole against clinical Trichosporon asahii isolates (n = 43) by NCCLS M27A reference microdilution method and explored the correlation between Etest and NCCLS reference method. Microdilution MIC ranges following 48 h of incubation were 1-8, 0.25-16, and 0.06-4 microg/ml for amphotericin B, fluconazole, and itraconazole, respectively. The corresponding Etest MIC ranges were determined as 0.125- > 8, 0.25- > 64, and 0.03-8 microg/ml. Of interest, Etest tended to produce lower amphotericin B MICs and widen the MIC range compared to microdilution. The influence of Etest on fluconazole and itraconazole MICs was in contrary with that observed for amphotericin B. Etest MICs of fluconazole and itraconazole tended to be higher than microdilution MICs. The wider range of amphotericin B MICs obtained by using Etest methodology may facilitate discrimination of isolates with reduced susceptibility to amphotericin B. However, clinical significance of these findings remain yet unknown and determination of MIC breakpoint values is required.

In vitro antifungal susceptibilities of Trichosporon species

The in vitro activities of amphotericin B, itraconazole, fluconazole, voriconazole, posaconazole, and ravuconazole against 39 isolates of Trichosporon spp. were determined by the NCCLS M27-A microdilution method. The azoles tested appeared to be more potent than amphotericin B. Low minimal fungicidal concentration/MIC ratios were observed for voriconazole, posaconazole, and ravuconazole, suggesting fungicidal activity.

Review of the safety and efficacy of voriconazole

Voriconazole is a new triazole antifungal agent structurally related to fluconazole, but with improved potency and spectrum of activity. Voriconazole has good in vitro activity against Candida species, Cryptococcus neoformans, Aspergillus spp. and other mould spp. Initial clinical studies and case reports demonstrate efficacy with voriconazole against invasive aspergillosis and infections caused by C. neoformans, Scedosporium apiospermum, Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum. Voriconazole is available both as oral and iv. preparations and exhibits complex pharmacokinetics. This drug is metabolised by the cytochrome (CYP) P450 enzyme system and therefore, has potential drug interactions. This review evaluates the current literature regarding the safety and efficacy of voriconazole.