Comparative in vitro activity of voriconazole and itraconazole against fluconazole-susceptible and fluconazole-resistant clinical isolates of Candida species from Spain

Kolliphor® HS 15-cyclodextrin Complex for the Delivery of Voriconazole: Preparation, Characterization, and Antifungal Activity

BACKGROUND

This study aimed to reduce the amount of sulfobutylether-β-cyclodextrin (SBECD) used in the marketed voriconazole injections to meet the clinical needs of patients with moderate-to-severe renal impairment (creatinine clearance rate <50 mL/min).

OBJECTIVE

This study found that the surfactant Kolliphor® HS 15 (HS 15) and SBECD had significant synergistic effects on solubilizing voriconazole, and a novel voriconazole complex delivery system (VRC-CD/HS 15) was established.

METHODS

The complex system was characterized, and its antifungal activity was studied by dynamic light scattering, dialysis bag method, disk diffusion, and broth microdilution.

RESULTS

Compared with the control, its encapsulation efficiency (90.07±0.48%), drug loading (7.37±0.25%) and zeta potential (-4.36±1.37 mV) were increased by 1.54%, 41.19%, and 296.36%, respectively; its average particle size (13.92±0.00 nm) was reduced by 15.69%, so the complex system had better stability. Simultaneously, its drug release behavior was similar to that of the control, and it was a first-order kinetic model. Antifungal studies indicated that the complex system had noticeable antifungal effects. With the increase of drug concentration, the inhibition zone increased. The minimum inhibitory concentrations of the complex system against Cryptococcus neoformans, Aspergillus niger and Candida albicans were 0.0313 μg/mL, 1 μg/mL and 128 μg/mL, respectively.

CONCLUSION

It showed a significant inhibitory effect on C. neoformans and had a visible therapeutic effect on Kunming mice infected with C. neoformans. Consequently, VRC-CD/HS 15 had better physicochemical properties and still had an apparent antifungal effect, and was promising as a potential alternative drug for clinical application.

Voriconazole

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Voriconazole: therapeutic review of a new azole antifungal

The new triazole antifungal, voriconazole (Vfend, Pfizer Ltd), was developed for the treatment of life-threatening fungal infections in immunocompromised patients. The drug, which is available for both oral and intravenous administration, has broad-spectrum activity against pathogenic yeasts, dimorphic fungi and opportunistic moulds. Unlike fluconazole (Diflucan, Pfizer Ltd), voriconazole has potent in vitro activity against Aspergillus spp., Fusarium spp. and Scedosporium apiospermum. In Phase II/III trials, voriconazole was well-tolerated and had excellent clinical efficacy in patients with fluconazole-sensitive and -resistant candida infection, aspergillosis, and various refractory fungal infections. The US Food and Drug Administration approved voriconazole in May 2002 for the treatment of invasive aspergillosis, and serious infections caused by Fusarium and S. apiospermum in patients who are intolerant of, or refractory to, other antifungal agents. In Europe, voriconazole is approved by the European Medicines Agency for the treatment of invasive aspergillosis, serious infections caused by Fusarium and S. apiospermum, and fluconazole-resistant serious invasive candida infections (including C. krusei).

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® 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® 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® 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.

Efficacy and safety of voriconazole as an additive in Optisol GS: a preservation medium for corneal donor tissue

PURPOSE

To assess the endothelial toxicity and the microbiological efficacy of voriconazole (100 microg/mL) as an antimicrobial additive to Optisol GS.

METHODS

A total of 533 donor rims were studied. One half of each donor rim was placed in standard Optisol GS and the other half rim in Optisol GS fortified with voriconazole (100 microg/mL). All rims were refrigerated for 24 hours at 3 degrees C and placed in thioglycolate broth and incubated at 37 degrees C for 7 days. A pair of donor buttons not used in transplantation was stored for 2 days in each solution and examined for endothelial changes with electron microscopy (EM). A second pair of cornea buttons was examined for toxicity by endothelial staining with 0.3% trypan blue and 0.2% alizarin red.

RESULTS

Seven of 533 corneal rim cultures were positive for fungal organisms in the Optisol GS group. No rims were positive for fungal growth in the voriconazole-fortified Optisol GS medium. The difference was statistically significant (P = 0.015; Fisher exact test). There was no difference in the cellular morphology of the button stored in voriconazole fortified Optisol GS compared with Optisol GS using EM. In the bioassay, the percentage of nonviable cells in the voriconazole-fortified medium compared with the control medium was nonsignificant (P < 0.05, Student t test).

CONCLUSIONS

Voriconazole seems to be safe as a fortifying agent for cornea storage medium. It significantly reduces the rate of positive fungal rim cultures and shows no signs of endothelial cytotoxicity as viewed by EM and by a bioassay of trypan blue and alizarin red.

Antifungal drug susceptibility profile of Pichia anomala isolates from patients presenting with nosocomial fungemia

In vitro susceptibility of 58 isolates of Pichia anomala to five antifungal drugs using two broth microdilution methods (CLSI and EUCAST) was analyzed. Low susceptibility to itraconazole was observed. Fluconazole, voriconazole, amphotericin B, and caspofungin showed good antifungal activity, although relatively high drug concentrations were necessary to inhibit the isolates.

Voriconazole and multidrug resistance in Candida albicans

In vitro activity of voriconazole against fluconazole-resistant Candida albicans clinical isolates with identified molecular basis of multidrug resistance (MDR) and recombinant Saccharomyces cerevisiae expressing C. albicans genes coding for major multidrug transporters, CaCdr1p, CaCdr2p or CaMdr1p, was compared with that of fluconazole, ketoconazole and clotrimazole. It was found that overexpression of the MDR genes made the yeast cells less susceptible to voriconazole. The voriconazole resistance indexes, defined as a ratio of minimum inhibitory concentrations (MICs) determined for MDR and sensitive cells, were comparable with those determined for fluconazole. Voriconazole effectively competed with rhodamine 6G for the active efflux mediated by CaCdr1p and CaCdr2p.

Voriconazole: a broad spectrum triazole for the treatment of serious and invasive fungal infections

For many years, serious systemic fungal infections have been treated with amphotericin B or narrow-spectrum azole antifungals. These treatments have been effective in many patients, but are associated with tolerability or pharmacokinetic concerns, or suboptimal antifungal activity in some patient groups. Voriconazole is a second-generation triazole with an extended spectrum of activity offering the potential to treat life-threatening fungal infections. The drug is available for intravenous or oral administration and has been shown to be effective in invasive aspergillosis, fluconazole-susceptible and -resistant candidiasis, and infections caused by various other fungal pathogens, including some formerly refractory organisms. Voriconazole is generally well tolerated with transient visual disturbances, liver enzyme abnormalities and skin rashes being the most common adverse events reported, but these rarely lead to treatment discontinuation.

In VitroActivities of Voriconazole and Five Licensed Antifungal Agents AgainstCandida dubliniensis:Comparison of CLSI M27-A2, Sensititre YeastOne, Disk Diffusion, and Etest Methods

We compared the in vitro activity of six antifungal agents against 62 isolates of Candida dubliniensis by the Clinical Laboratory Standards Institute (CLSI [formerly National Committee for the Clinical Laboratory Standards]) M27-A2, Sensititre YeastOne, disk diffusion, and Etest methods and we studied the effect of the time of reading. For the azoles, voriconazole was the most potent in vitro followed by fluconazole, ketoconazole, and itraconazole. All the isolates were susceptible to amphotericin B and flucytosine. The highest rate of resistance was obtained against itraconazole with a high number of isolates defined as susceptible dose-dependent. At 24 hr, 100% of the isolates were susceptible to ketoconazole, amphotericin B, and flucytosine, 98% susceptible to voriconazole and fluconazole, and 95% for itraconazole. At 48 hr, 100% of the isolates remained susceptible for flucytosine and amphotericin B, 95% for voriconazole, 93% for fluconazole, 90% for ketoconazole, and 82% for itraconazole. The agreement between the CLSI and the other methods was better at 24 than 48 hr.

Correlation of MIC with outcome for Candida species tested against voriconazole: analysis and proposal for interpretive breakpoints

Developing interpretive breakpoints for any given organism-drug combination requires integration of the MIC distribution, pharmacokinetic and pharmacodynamic parameters, and the relationship between the in vitro activity and outcome from both in vivo and clinical studies. Using data generated by standardized broth microdilution and disk diffusion test methods, the Antifungal Susceptibility Subcommittee of the Clinical and Laboratory Standards Institute has now proposed interpretive breakpoints for voriconazole and Candida species. The MIC distribution for voriconazole was determined using a collection of 8,702 clinical isolates. The overall MIC90 was 0.25 microg/ml and 99% of the isolates were inhibited at < or = 1 microg/ml of voriconazole. Similar results were obtained for 1,681 Candida isolates (16 species) from the phase III clinical trials. Analysis of the available data for 249 patients from six phase III voriconazole clinical trials demonstrated a statistically significant correlation (P = 0.021) between MIC and investigator end-of-treatment assessment of outcome. Consistent with parallel pharmacodynamic analyses, these data support the following MIC breakpoints for voriconazole and Candida species: susceptible (S), < or = 1 microg/ml; susceptible dose dependent (SDD), 2 microg/ml; and resistant (R), > or = 4 microg/ml. The corresponding disk test breakpoints are as follows: S, > or = 17 mm; SDD, 14 to 16 mm; and R, < or = 13 mm.

Fungal keratitis at the new york eye and ear infirmary

INTRODUCTION

This study was designed to review the clinical experience at our institution with fungal keratitis during a 16-year period.

MATERIALS AND METHODS

A review of the clinical and microbiology records of the New York Eye and Infirmary identified 61cases of fungal keratitis in 57 patients between January 1, 1987 and June 1, 2003. The medical records of all patients were retrospectively reviewed to better delineate patient demographics, risk factors, etiologic organisms, treatment, and outcomes.

RESULTS

A total of 5083 positive corneal cultures were recorded'from January 1, 1987 to June 1, 2003. Sixty-one eyes in 57 patients (37 women) were positive for fungus (1.2%). Three'patients had bilateral simultaneous infections. Candida albicans accounted for 29 of 61 cases (48%). Human immunodeficiency virus (HIV) seropositivity (15 eyes), chronic ocular surface disease (14 eyes), and trauma (7 eyes) were the most commonly associated risk factors.

CONCLUSIONS

Our experience with fungal keratitis in the northeastern United States appears to be different than those reported from other areas of the United States. Serologic positivity for HIV and chronic ocular surface disease were the most common associated risk factors followed by trauma, herpes simplex keratitis, and contact lens use. Candida species predominated, whereas filamentous fungi were uncommon.

Interpretive breakpoints for fluconazole and Candida revisited: a blueprint for the future of antifungal susceptibility testing

Developing interpretive breakpoints for any given organism-drug combination requires integration of the MIC distribution, pharmacokinetic and pharmacodynamic parameters, and the relationship between in vitro activity and outcome from both in vivo and clinical studies. Previously, the Subcommittee for Antifungal Testing of the Clinical and Laboratory Standards Institute (CLSI [formerly National Committee for Clinical Laboratory Standards]) proposed MIC interpretive breakpoints for fluconazole and Candida spp. These breakpoints were considered to be somewhat weak, because the clinical data supporting them came largely from mucosal infections and there were very few infections involving strains with elevated fluconazole MICs. We readdress the issue of fluconazole breakpoints for Candida by using published clinical and microbiologic data to provide further validation of the breakpoints proposed by the CLSI in 1997. We also address interpretive breakpoints for agar disk diffusion testing of fluconazole. The MIC distribution for fluconazole was determined with a collection of 13,338 clinical isolates. The overall MIC at which 90% of the isolates were inhibited was 8 microg/ml: 91% were susceptible (S) at a MIC of or= 64 microg/ml). Similar results were obtained for 2,190 isolates from randomized clinical trials. Analysis of available data for 1,295 patient-episode-isolate events (692 represented mucosal infections and 603 represented invasive infections) from 12 published clinical studies demonstrated an overall success rate of 77%, including 85% for those episodes in which the fluconazole MIC was or= 64 microg/ml) isolates. Pharmacodynamic analysis demonstrated a strong relationship between MIC, fluconazole dose, and outcome. A dose/MIC ratio of approximately 25 was supportive of the following susceptibility breakpoints for fluconazole and Candida spp.: S, MIC or= 64 microg/ml. The corresponding disk test breakpoints are as follows: S, >or=19 mm; SDD, 15 to 18 mm; R, Collapse

Key Words Collapse

MESH Headings

• Antifungal Agents/administration & dosage
• Antifungal Agents/pharmacology
• Antifungal Agents/therapeutic use
• Candida/drug effects
• Candidiasis/drug therapy
• Clinical Trials as Topic
• Dose-Response Relationship, Drug
• Drug Resistance, Fungal
• Fluconazole/pharmacokinetics
• Fluconazole/pharmacology
• Fluconazole/therapeutic use
• Humans
• Microbial Sensitivity Tests/standards
• Treatment Outcome

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Grants Collapse

Affiliation(s)

M A Pfaller Department of Pathology, Medical Microbiology Division, C606 GH, University of Iowa College of Medicine, Iowa City, 52242, USA.
D J Diekema
D J Sheehan

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Voriconazole versus a regimen of amphotericin B followed by fluconazole for candidaemia in non-neutropenic patients: a randomised non-inferiority trial

BACKGROUND

Voriconazole has proven efficacy against invasive aspergillosis and oesophageal candidiasis. This multicentre, randomised, non-inferiority study compared voriconazole with a regimen of amphotericin B followed by fluconazole for the treatment of candidaemia in non-neutropenic patients.

METHODS

Non-neutropenic patients with a positive blood culture for a species of candida and clinical evidence of infection were enrolled. Patients were randomly assigned, in a 2:1 ratio, either voriconazole (n=283) or amphotericin B followed by fluconazole (n=139). The primary efficacy analysis was based on clinical and mycological response 12 weeks after the end of treatment, assessed by an independent data-review committee unaware of treatment assignment.

FINDINGS

Of 422 patients randomised, 370 were included in the modified intention-to-treat population. Voriconazole was non-inferior to amphotericin B/fluconazole in the primary efficacy analysis, with successful outcomes in 41% of patients in both treatment groups (95% CI for difference -10.6% to 10.6%). At the last evaluable assessment, outcome was successful in 162 (65%) patients assigned voriconazole and 87 (71%) assigned amphotericin B/fluconazole (p=0.25). Voriconazole cleared blood cultures as quickly as amphotericin B/fluconazole (median time to negative blood culture, 2.0 days). Treatment discontinuations due to all-cause adverse events were more frequent in the voriconazole group, although most discontinuations were due to non-drug-related events and there were significantly fewer serious adverse events and cases of renal toxicity than in the amphotericin B/fluconazole group.

INTERPRETATION

Voriconazole was as effective as the regimen of amphotericin B followed by fluconazole in the treatment of candidaemia in non-neutropenic patients, and with fewer toxic effects.

RELEVANCE TO PRACTICE

There are several options for treatment of candidaemia in non-neutropenic patients, including amphotericin B, fluconazole, voriconazole, and echinocandins. Voriconazole can be given both as initial intravenous treatment and as an oral stepdown agent.

Voriconazole susceptibility of yeasts isolated from the mouths of patients with advanced cancer

The in vitro activity of voriconazole was compared with those of fluconazole and itraconazole against 270 clinical isolates of yeasts from the mouths of patients receiving palliative care for advanced cancer. A broth micro-dilution assay as described by the National Committee for Clinical Laboratory Standards was employed for determination of MICs. Of the 270 isolates, 206 (76 %) were fluconazole sensitive and 64 were fluconazole resistant. Voriconazole showed more potent activity than either fluconazole or itraconazole, including against some isolates resistant to both fluconazole and itraconazole. However, for fluconazole-resistant isolates, the MICs of itraconazole and voriconazole were proportionally higher than for the fluconazole-susceptible isolates, suggesting cross-resistance. Voriconazole may be a useful additional agent for the management of oral fungal infections caused by strains resistant to fluconazole and itraconazole, but susceptibility cannot be assumed and in vitro MIC determination is recommended prior to its use.

Voriconazole: review of a broad spectrum triazole antifungal agent

Voriconazole is a second-generation triazole antifungal agent, structurally derived from fluconazole with an extended spectrum of activity against a wide variety of yeasts and moulds. Developed for the treatment of life-threatening fungal infections, it appears to be an effective therapy option for invasive aspergillosis, fluconazole-resistant candidiasis and refractory or less-common invasive fungal infections. It is available for both oral and intravenous administration and is characterised by an acceptable safety and tolerability spectrum.

In vitro susceptibility testing of Candida and Aspergillus spp. to voriconazole and other antifungal agents using Etest®: results of a French multicentre study

Minimum inhibitory concentrations (MICs) of the antifungal agent voriconazole were determined using the Etest and compared with those of amphotericin B, itraconazole and fluconazole using 1986 clinical isolates of Candida spp. Voriconazole MICs were also compared with those of amphotericin B and itraconazole using 391 clinical isolates of Aspergillus spp. Voriconazole was found to have more potent activity and lower MIC values than amphotericin B, itraconazole and fluconazole against C. albicans, C. tropicalis, C. parapsilosis and C. kefyr. Against C. glabrata and C. krusei, voriconazole was more active than either of the other two azole antifungals but had similar activity to amphotericin B. For species of Aspergillus, MIC values of voriconazole were lower than those of amphotericin B and itraconazole against A. fumigatus and A. flavus, and were similar to those of amphotericin B against A. niger. Against A. terreus, MIC values for voriconazole and itraconazole were similar. A. terreus is known to be resistant to amphotericin B, and this was reflected in higher MIC values compared with those of voriconazole and itraconazole. Voriconazole therefore compares very favourably with other antifungal agents against a large number of clinical isolates of Candida and Aspergillus spp.

Influence of voriconazole and fluconazole on reconstituted multilayered oesophageal epithelium infected by Candida albicans

Reconstituted multilayered oesophageal epithelium appears to be a good basis to test the efficacy of voriconazole (VOR) and fluconazole (FLU) in the tissue. The resulting model of a Candida oesophagitis was approaching the in vivo situation. We infected the tissue with 2 x 10(6) cfu of the Candida albicans strain SC5314. In the trials with FLU we also used clinical strains. Four hours after infection a good growth of C. albicans appeared mainly with hyphae on the surface of the tissue and a tendency to invasion. The destruction of the tissue began after 36 h. VOR (2 and 16 microg ml-1, respectively) prevented the penetration of hyphae into the tissue, when it was given 4-8 h after infection. It was less effective in reduction of Candida growth on the tissue surface. When VOR was given 16-24 h postinfection, the Candida infiltration stopped more slowly. Thirty-six hours after infection VOR application could not stop the destruction of the tissue despite reducing the fungi. The results with FLU (32 microg ml-1) were in principle the same, but not so distinct. FLU seems to be more effective against clinical strains of C. albicans than against the type strain.

New antifungal agents

Currently, use of standard antifungal therapies can be limited because of toxicity, low efficacy rates, and drug resistance. New formulations are being prepared to improve absorption and efficacy of some of these standard therapies. Various new antifungals have demonstrated therapeutic potential. These new agents may provide additional options for the treatment of superficial fungal infections and they may help to overcome the limitations of current treatments. Liposomal formulations of AmB have a broad spectrum of activity against invasive fungi, such as Candida spp., C. neoformans, and Aspergillus spp., but not dermatophyte fungi. The liposomal AmB is associated with significantly less toxicity and good rates of efficacy, which compare or exceed that of standard AmB. These factors may provide enough of an advantage to patients to overcome the increased costs of these formulations. Three new azole drugs have been developed, and may be of use in both systemic and superficial fungal infections. Voriconazole, ravuconazole, and posaconazole are triazoles, with broad-spectrum activity. Voriconazole has a high bioavailability, and has been used with success in immunocompromised patients with invasive fungal infections. Ravuconazole has shown efficacy in candidiasis in immunocompromised patients, and onychomycosis in healthy patients. Preliminary in vivo studies with posaconazole indicated potential use in a variety of invasive fungal infections including oropharyngeal candidiasis. Echinocandins and pneumocandins are a new class of antifungals, which act as fungal cell wall beta-(1,3)-D-glucan synthase enzyme complex inhibitors. Caspofungin (MK-0991) is the first of the echinocandins to receive Food and Drug Administration approval for patients with invasive aspergillosis not responding or intolerant to other antifungal therapies, and has been effective in patients with oropharyngeal and esophageal candidiasis. Standardization of MIC value determination has improved the ability of scientists to detect drug resistance in fungal species. Cross-resistance of fungal species to antifungal drugs must be considered as a potential problem to future antifungal treatment, and so determination of susceptibility of fungal species to antifungal agents is an important component of information in development of new antifungal agents. Heterogeneity in susceptibility of species to azole antifungals has been noted. This heterogeneity suggests that there are differences in activity of azoles, and different mechanisms of resistance to the azoles, which may explain the present lack of cross-resistance between some azoles despite apparent structural similarities. The mechanisms of azole action and resistance themselves are not well understood, and further studies into azole susceptibility patterns are required.

Mutations in Aspergillus fumigatus resulting in reduced susceptibility to posaconazole appear to be restricted to a single amino acid in the cytochrome P450 14alpha-demethylase

To better understand the molecular basis of posaconazole (POS) resistance in Aspergillus fumigatus, resistant laboratory isolates were selected. Spontaneous mutants arose at a frequency of 1 in 10(8) and fell into two susceptibility groups, moderately resistant and highly resistant. Azole resistance in A. fumigatus was previously associated with decreased drug accumulation. We therefore analyzed the mutants for changes in levels of transcripts of genes encoding efflux pumps (mdr1 and mdr2) and/or alterations in accumulation of [(14)C]POS. No changes in either pump expression or drug accumulation were detected. Similarly, there was no change in expression of cyp51A or cyp51B, which encode the presumed target site for POS, cytochrome P450 14alpha-demethylase. DNA sequencing revealed that each resistant isolate carried a single point mutation in residue 54 of cyp51A. Mutations at the same locus were identified in three clinical A. fumigatus isolates exhibiting reduced POS susceptibility but not in susceptible clinical strains. To verify that these mutations were responsible for the resistance phenotype, we introduced them into the chromosome of a POS-susceptible A. fumigatus strain under the control of the glyceraldehyde phosphate dehydrogenase promoter. The transformants exhibited reductions in susceptibility to POS comparable to those exhibited by the original mutants, confirming that point mutations in the cyp51A gene in A. fumigatus can confer reduced susceptibility to POS.

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.

Present status of the detection of antifungal resistance: the perspective from both sides of the ocean

The NCCLS reference methodology for antifungal susceptibility testing is a new milestone of the evolution of medical mycology. The use of this methodology however, is not problem-free. At present, major limitations are a trailing phenomenon with azoles, unreliable detection of resistance to amphotericin B, poor growth of some organisms and unpractical procedures for the clinical laboratory. Herein a overview of NCCLS guidelines for yeasts and filamentous fungi is presented. Likewise, a review of studies conducted trying to overcome the limitations of reference procedures is also included. Several alternative approaches are reviewed as alternative media, inoculum size and incubation time. Modifications of reading procedure and endpoint determination are also evaluated. Agar diffusion methods and other methods for susceptibility testing are cited. Finally, we discuss the data on correlation of the in vitro results with the in vivo activity.

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

Voriconazole (VfendTM) 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 microg/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 microg/ml, respectively. For four of the six Aspergillus spp. evaluated, voriconazole MICs (< 0.03 to 2 microg/ml) were lower than amphotericin B (0.25 to 4 microg/ml) and similar to itraconazole MICs. Voriconazole fungistatic activity against Fusarium spp. has been variable. Against E oxysporum and F. solani, most studies showed MICs ranging from 0.25 to 8 microg/ml. Voriconazole had excellent fungistatic activity against five of the six species of dimorphic fungi evaluated (MIC90s < 1.0 microg/ml). The exception was Sporothrix schenckii (MIC90s and geometric mean MICs > or = 8 microg/ml). Only amphotericin B had good fungistatic activity against the Zygomycetes species (voriconazole MICs ranged from 2 to > 32 microg/ml). Voriconazole showed excellent in vitro activity (MICs < 0.03 to 1.0 microg/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.

Synergism of voriconazole and terbinafine against Candida albicans isolates from human immunodeficiency virus-infected patients with oropharyngeal candidiasis

The synergism of voriconazole (VRC) and terbinafine was studied by using 39 genotypically defined clinical Candida albicans isolates that were cross-resistant to fluconazole and VRC and serial isolates that gradually developed azole resistance. Synergy was noticed in 100% (eight of eight) of the strains that were resistant to VRC. Antagonism was not observed.

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

Voriconazole is a promising azole effective against a variety of fungi, including yeasts. In this study, we tested in vitro activities of voriconazole, fluconazole, itraconazole and amphotericin B against some ATCC and reference strains and 250 clinical yeast isolates. We also evaluated the effect of time of reading on MIC results. Voriconazole was the most active agent against Candida and Trichosporon isolates, including the putatively fluconazole-resistant C. krusei (MIC(90) 0.25 microg/ml) and C. glabrata (MIC(90) 0.5 microg/ml). Amphotericin B MICs were scattered in a considerably narrow range in both RPMI 1640 and Antibiotic Medium 3. MICs at 24 hours and 48 hours were similar in general for all antifungals tested. The highest percentage of strains that showed 24-hour and 48-hour MICs within +/-1-log(2) dilution was observed for amphotericin B tested in RPMI (99%), and the lowest for amphotericin B tested in Antibiotic Medium 3 (80%). In conclusion, voriconazole is very effective against a wide spectrum of Candida species and 24-hour readings could substitute 48-hour MIC evaluation.