Itraconazole resistance in Aspergillus fumigatus

Localised invasive sino-orbital aspergillosis: characteristic features

BACKGROUND/AIM

To describe the characteristic constellation of historical, clinical, radiographic, and histopathological findings of localised invasive sino-orbital aspergillosis based on the authors' recent experience of four consecutive cases presenting over a 6 month period. Treatment and outcome are reviewed.

METHODS

A case series of four patients with review of the English language literature.

RESULTS

There have been 17 reported cases of invasive sino-orbital aspergillosis in healthy individuals over the past 33 years. The authors report four patients who presented during a 6 month period with persistent and significant pain followed by progressive ophthalmic signs-clinical histories reflecting the literature. Similar imaging findings were also noted: focal hypodense areas within apical infiltrates on contrasted computed tomography correspond to abscesses seen at surgery, and sinus obliteration or involvement of the adjacent sinus lining was noted on magnetic resonance imaging. Bone erosion (often focal) was also seen. There is frequently a delay in making the correct diagnosis, and often disease progression occurs despite treatment.

CONCLUSIONS

The authors encountered four cases of invasive sino-orbital aspergillosis, three of which occurred in otherwise healthy individuals. The clinician must be aware of the characteristic presentation so that earlier diagnosis, management, and improved outcomes can be achieved.

History of the development of azole derivatives

Until the 1940s, relatively few agents were available for the treatment of systemic fungal infections. The development of the polyene antifungals represented a major advance in medical mycology. Although amphotericin B quickly became the mainstay of therapy for serious infections, its use was associated with infusion-related side-effects and dose-limiting nephrotoxicity. The continued search for new and less toxic antifungals led to the discovery of the azoles several decades later. Ketoconazole, the first available compound for the oral treatment of systemic fungal infections, was released in the early 1980s. For almost a decade, ketoconazole was regarded as the drug of choice in nonlife-threatening endemic mycoses. The introduction of the first-generation triazoles represented a second major advance in the treatment of fungal infections. Both fluconazole and itraconazole displayed a broader spectrum of antifungal activity than the imidazoles and had a markedly improved safety profile compared with amphotericin B and ketoconazole. Despite widespread use, however, these agents became subject to a number of clinically important limitations related to their suboptimal spectrum of activity, the development of resistance, the induction of hazardous drug-drug interactions, their less than optimal pharmacokinetic profile (itraconazole capsules), and toxicity. In order to overcome these limitations, several analogues have been developed. These so-called 'second-generation' triazoles, including voriconazole, posaconazole and ravuconazole, have greater potency and possess increased activity against resistant and emerging pathogens, in particular against Aspergillus spp. If the toxicity profile of these agents is comparable to or better than that of the first-generation triazoles and drug interactions remain manageable, then these compounds represent a true expansion of our antifungal arsenal.

In vitro evaluation of double and triple combinations of antifungal drugs against Aspergillus fumigatus and Aspergillus terreus

Microdilution broth checkerboard techniques based on the National Committee for Clinical Laboratory Standards methodology were used to study double and triple antifungal combinations against clinical isolates of Aspergillus fumigatus and A. terreus. The influences of the end-point definition (partial or complete inhibition) and the mode of reading (visually or spectrophotometrically) were determined. Interactions between antifungal drugs were also evaluated by agar diffusion tests. Combinations of caspofungin with either amphotericin B or voriconazole were additive for all the isolates, and antagonism was not observed. The interaction between caspofungin and flucytosine was synergistic for 62% of the isolates. In contrast, the interaction between voriconazole and flucytosine was never synergistic and antagonism was noted for 93% of the isolates. The triple combination of caspofungin with flucytosine and amphotericin B was synergistic for all the isolates tested. The triple combination of caspofungin with flucytosine and voriconazole was also mostly synergistic; but complex interactions were obtained for some isolates, with synergy or antagonism depending on the concentrations of caspofungin and voriconazole. Analysis of the influence of the reading technique on the results showed that spectrophotometric reading was a good alternative to the recommended visual reading. The results of these in vitro tests suggest that the activity of flucytosine as part of a double combination with caspofungin and as part of a triple combination with caspofungin and amphotericin B against Aspergillus spp. warrants further investigations. Animal studies are needed to evaluate the in vivo efficacies of these combinations.

Effect of aeration on gliotoxin production by Aspergillus fumigatus in its culture filtrate

Gliotoxin, one of the mycotoxins produced by Aspergillus fumigatus, has various, potent bioactivities. However, it has not been considered to be a toxic (or virulence) factor because of its slow production. The aim of the present study was to investigate the effects of aeration on the cytotoxicity of A. fumigatus culture filtrate, and to determine the optimal condition for the rapid production of gliotoxin from this fungus. Fungal culture filtrates were made in three different containers under various conditions of aeration and O2 concentration. These filtrates were compared in terms of their cytotoxicity on murine macrophages and analyzed by gas chromatography. The culture filtrate showed high cytotoxicity when it was made under highly aerated conditions, but it was significantly less cytotoxic when prepared under non-aerated conditions. The cytotoxic activity became evident within 15 h of culture at 20% O2, when the fungus had already started producing gliotoxin. The culture filtrates also contained some other as yet unidentified substances that might also to some extent contribute to the cytotoxicity. In light of these results, the authors propose that a highly aerated condition is responsible for the rapid production of gliotoxin, and that gliotoxin might play an important role in the respiratory infection by A. fumigatus, with other toxic substances acting additively or synergistically.

In vitro activities of three licensed antifungal agents against spanish clinical isolates of Aspergillus spp

The aim of the present study was to identify retrospectively trends in the species distributions and the susceptibility patterns of Aspergillus species causing fungal infections in Spanish medical centers from 2000 to 2002. The susceptibilities of 338 isolates to amphotericin B, itraconazole, and voriconazole were tested. Aspergillus fumigatus was the most common species (54.7%), followed by Aspergillus terreus (14.8%) and Aspergillus flavus (13.9%). Non-A. fumigatus species were encountered in 45.3% of the samples studied. The majority of Aspergillus isolates were obtained from respiratory tract specimens, followed by ear and skin samples. The geometric mean (GM) MIC of amphotericin B was 0.56 micro g/ml, and the amphotericin B MIC was >2 micro g/ml for 16 isolates (4.7%). Nine of them were A. terreus. The GM MIC of itraconazole was 0.37, and the itraconazole MIC was >4 micro g/ml for 12 (3.5%) isolates. The voriconazole MICs were also high for 8 of the 12 strains for which itraconazole MICs were high (voriconazole MIC range, 2 to 8 micro g/ml).

Use of turbidimetric growth curves for early determination of antifungal drug resistance of filamentous fungi

A previously described microbroth kinetic system (J. Meletiadis, J. F. Meis, J. W. Mouton, and P. E. Verweij, J. Clin. Microbiol. 39:478-484, 2001) based on continuous monitoring of changes in the optical density of fungal growth was used to describe turbidimetric growth curves of different filamentous fungi in the presence of increasing concentrations of antifungal drugs. Therefore, 24 clinical mold isolates, including Rhizopus oryzae, Aspergillus fumigatus, Aspergillus flavus, and Scedosporium prolificans, were tested against itraconazole, terbinafine, and amphotericin B according to NCCLS guidelines. Among various parameters of the growth curves, the duration of the lag phase was strongly affected by the presence of antifungal drugs. Exposure to increasing drug concentrations resulted in prolonged lag phases of the turbidimetric growth curves. The lag phases of the growth curves at drug concentrations which resulted in more than 50% growth (for itraconazole and terbinafine) and more than 75% growth (for amphotericin B) after 24 h of incubation for R. oryzae, 48 h for Aspergillus spp., and 72 h for S. prolificans were 4 h longer than the lag phases of the growth curves at the corresponding drug-free growth controls which varied from 4.4 h for R. oryzae, 6.5 h for A. flavus, 7.9 h for A. fumigatus, and 11.6 h for S. prolificans. The duration of the lag phases showed small experimental and interstrain variability, with differences of less than 2 h in most of the cases. Using this system, itraconazole and terbinafine resistance (presence of >50% growth) as well as amphotericin B resistance (presence of >75% growth) was determined within incubation periods of 5.0 to 7.7 h for R. oryzae (for amphotericin B resistance incubation for up to 12 h was required), 8.8 to 11.4 h for A. fumigatus, 6.7 to 8.5 h for A. flavus, and 13 to 15.6 h for S. prolificans while awaiting formal MIC determination by the NCCLS reference method.

Voriconazole for serious fungal infections

Voriconazole is a new second generation triazole effective against a wide spectrum of fungal pathogens. A randomised, controlled trial has shown it to be superior to amphotericin B in invasive aspergillosis, and it is a potential alternative to amphotericin B in neutropenic sepsis and to fluconazole in oesophageal candidiasis. Early clinical reports and in vitro susceptibility data suggest that it may also be a valuable antifungal against fluconazole-resistant Candida species and certain emerging fungal pathogens, which cause infections that are often refractory to conventional therapies. There is limited evidence of azole cross-resistance of clinical importance. Voriconazole is available as intravenous and oral formulations and has excellent tissue penetration and a good safety profile, the main problems being transient visual impairment and hepatotoxicity in patients with liver disease. It is metabolised by cytochrome P-450 isoenzymes causing important drug interactions but, in contrast to amphotericin B, is safe in renal failure and rarely causes infusion-related reactions. This review outlines the pharmacology of voriconazole and focuses on its clinical applications and safety profile.

Itraconazole--perspectives for the management of invasive aspergillosis

Itraconazole has become an important option in the management of invasive aspergillosis. The compound has potent and broad spectrum antifungal activity in vitro against Aspergillus spp. with a species- and strain dependent fungicidal mode of action. In vivo, the antifungal efficacy of itraconazole has been demonstrated in several non-immunocompromised and immunocompromised animal models of disseminated and invasive pulmonary aspergillosis. Itraconazole is available in oral and intravenous formulations, displays non-linear plasma pharmacokinetics, and is usually well tolerated. Non-comparative clinical data of itraconazole for therapy of suspected or proven invasive aspergillosis suggest response rates similar to those of conventional amphotericin B; however, the experience with itraconazole for induction therapy of invasive aspergillosis is limited, particularly in profoundly neutropenic patients. Itraconazole has an important role for consolidation and maintenance therapy of patients with invasive aspergillosis, and novel combination therapies involving itraconazole are currently under intensive preclinical investigation as to their usefulness for primary therapy.

Multiple resistance mechanisms among Aspergillus fumigatus mutants with high-level resistance to itraconazole

A collection of Aspergillus fumigatus mutants highly resistant to itraconazole (RIT) at 100 micro g ml(-1) were selected in vitro (following UV irradiation as a preliminary step) to investigate mechanisms of drug resistance in this clinically important pathogen. Eight of the RIT mutants were found to have a mutation at Gly54 (G54E, -K, or -R) in the azole target gene CYP51A. Primers designed for highly conserved regions of multidrug resistance (MDR) pumps were used in reverse transcriptase PCR amplification reactions to identify novel genes encoding potential MDR efflux pumps in A. fumigatus. Two genes, AfuMDR3 and AfuMDR4, showed prominent changes in expression levels in many RIT mutants and were characterized in more detail. Analysis of the deduced amino acid sequence encoded by AfuMDR3 revealed high similarity to major facilitator superfamily transporters, while AfuMDR4 was a typical member of the ATP-binding cassette superfamily. Real-time quantitative PCR with molecular beacon probes was used to assess expression levels of AfuMDR3 and AfuMDR4. Most RIT mutants showed either constitutive high-level expression of both genes or induction of expression upon exposure to itraconazole. Our results suggest that overexpression of one or both of these newly identified drug efflux pump genes of A. fumigatus and/or selection of drug target site mutations are linked to high-level itraconazole resistance and are mechanistic considerations for the emergence of clinical resistance to itraconazole.

In vitro susceptibility testing of filamentous fungi: comparison of Etest and reference M38-A microdilution methods for determining posaconazole MICs

The performance of the Etest for posaconazole susceptibility testing of 72 isolates of filamentous fungi was assessed in comparison with the National Committee for Clinical Laboratory Standards (NCCLS) approved standard broth microdilution method (M38-A). The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48h at 35 degrees C. Etest MICs were determined with RPMI agar containing 2% glucose and were read after incubation for 48h at 35 degrees C. The isolates included Aspergillus fumigatus, A. flavus, A. nidulans, A. niger, A. versicolor, A. oryzae, A. terreus, Cladosporium spp., Curvularia sp., Exophiala sp., Fusarium spp., Paecilomyces spp., Pithomyces sp., Penicillium spp. and Scedosporium apiospermum. Overall agreement between Etest and microdilution MICs was 84% for Aspergillus spp. and 100% for the less common opportunistic molds, with the exception of Penicillium spp. (67%). Where a discrepancy was observed between Etest and the reference method, the Etest tended to give lower values. The Etest method using RPMI agar appears to be a useful method for determining posaconazole susceptibilities of filamentous fungi.

A point mutation in the 14alpha-sterol demethylase gene cyp51A contributes to itraconazole resistance in Aspergillus fumigatus

The genes encoding 14alpha-sterol demethylases (cyp51A and cyp51B) were analyzed in 12 itraconazole (ITC)-resistant and three ITC-susceptible clinical isolates of Aspergillus fumigatus. Six ITC-resistant strains exhibited a substitution of another amino acid for glycine at position 54, which is located at a very conserved region of the Cyp51A protein. The cyp51A gene from the A. fumigatus wild-type strain (CM-237) was replaced with the mutated cyp51A gene copy of an ITC-resistant strain (AF-72). Two transformants exhibited resistance to ITC, both of which had incorporated the mutated copy of the cyp51A gene.

Role of itraconazole in haematology/oncology

The antifungal agents most frequently used in prophylaxis and treatment are amphotericin B (and its new lipid forms) and azoles such as fluconazole, itraconazole, and more recently voriconazole. This review assesses the role of itraconazole in paediatric haematology/oncology practice. Its broader spectrum of activity and availability in oral and intravenous forms allow a flexible approach in the management of fungal infections.

In vitro susceptibility testing of Aspergillus spp.: comparison of Etest and reference microdilution methods for determining voriconazole and itraconazole MICs

The performance of the Etest for voriconazole and for itraconazole susceptibility testing of 376 isolates of Aspergillus spp. was assessed in comparison with the National Committee for Clinical Laboratory Standards (NCCLS) proposed standard microdilution broth method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48 h at 35 degrees C. Etest MICs were determined with RPMI agar containing 2% glucose and were read after incubation for 48 h at 35 degrees C. The isolates included A. fumigatus, A. flavus, A. niger, A. terreus, A. versicolor, A. glaucus, A. nidulans, A. ustus, and A. sydowii. Overall agreement percentages between the Etest and microdilution MICs were 97.6% for voriconazole and 95.8% for itraconazole. Where a discrepancy was observed between Etest and the reference method, the Etest tended to give lower values with voriconazole and higher values with itraconazole. The Etest method using RPMI agar appears to be a useful method for determining the voriconazole and itraconazole susceptibilities of Aspergillus spp.

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.

Antifungal agents of use in animal health--chemical, biochemical and pharmacological aspects

A limited number of antifungal agents is licensed for use in animals, however, many of those available for the treatment of mycoses in humans are used by veterinary practitioners. This review includes chemical aspects, spectra of activity, mechanisms of action and resistance, adverse reactions and drug interactions of the antifungals in current use.

Evaluation of broth microdilution testing parameters and agar diffusion Etest procedure for testing susceptibilities of Aspergillus spp. to caspofungin acetate (MK-0991)

The NCCLS M38-A document does not describe guidelines for testing caspofungin acetate (MK-0991) and other echinocandins against molds. This study evaluated the susceptibilities of 200 isolates of Aspergillus fumigatus, A. flavus, A. nidulans, A. niger, and A. terreus to caspofungin (MICs and minimum effective concentrations [MECs]) by using standard RPMI 1640 (RPMI) and antibiotic medium 3 (M3), two inoculum sizes (10(3) and 10(4) CFU/ml), and two MIC determination criteria (complete [MICs-0] and prominent growth inhibition [MICs-2]) at 24 and 48 h. Etest MICs were also determined. In general, caspofungin MIC-2 and MEC pairs were comparable with both media and inocula (geometric mean ranges of MECs and MICs, respectively, with larger inoculum: 0.12 to 0.64 microg/ml and 0.12 to 0.44 microg/ml with RPMI versus 0.04 to 0.51 microg/ml and 0.03 to 0.21 microg/ml with M3); however, MEC results were less influenced by testing conditions than MICs, especially with the larger inoculum. Overall, the agreement between caspofungin Etest MICs and broth dilution values was higher with MECs obtained with M3 (>90%) and the large inoculum than under the other testing conditions. Because RPMI is a more stable and chemically defined medium than M3, the determination at 24 h of the easier visual MECs with RPMI and the inoculum recommended in the M38-A document appears to be a suitable procedure at present for in vitro testing of caspofungin against Aspergillus spp. Future in vitro correlations with in vivo outcome of both microdilution and Etest procedures may detect more-relevant testing conditions.

[Clinical relevance of mechanisms of antifungal drug resistance in filamentous fungi]

In the last years, the incidence of the invasive infection by moulds has increased. Also, the characteristics of invasive mycosis are changing due to the description of new pathogenic species and also because strains and species resistant to antifungal drugs are appearing. The development of mould antifungal drug resistance is the inevitable and logical consequence of their clinical use, although the frequency and clinical relevance of this is unknown. In this text current mould antifungal drugs resistance mechanisms are reviewed. The study of molecular mechanisms of antifungal drug resistance is the most valuable strategy to resistance development control and also in helping to develop safer and more active molecules able to avoid them. In the meanwhile is important the correct use of the available tools: epidemiological surveillance of resistance emergence and to use all the efforts towards prompt diagnosis in order to accomplish an adequate and effective treatment.

In-vitro activities of terbinafine, itraconazole and amphotericin B against Aspergillus and Cladosporium species

The in vitro fungicidal and fungistatic activities of terbinafine were compared with those of itraconazole and amphotericin B against Aspergillus (n=63) and Cladosporium (n=21) isolates. The broth macrodilution modification of NCCLS reference method for filamentous fungi (M38-P) was used to assess the minimum inhibitory concentrations (MICs). Our data show that the in vitro activities of terbinafine were comparable to those of itraconazole and amphotericin B against the Aspergillus spp and Cladosporium strains tested. Despite strain-dependent variabilities, in general, itraconazole's activity was similar to that of amphotericin B against strains of Aspergillus and Cladosporium. Our data suggest that terbinafine may be useful in the treatment of Aspergillus and Cladosporium infections.

Optimal testing conditions for determining MICs and minimum fungicidal concentrations of new and established antifungal agents for uncommon molds: NCCLS collaborative study

This collaborative three-center study evaluated NCCLS M38-A document testing conditions and other testing conditions for the antifungal susceptibility testing of 35 isolates of Aspergillus nidulans, A. terreus, Bipolaris hawaiiensis, B. spicifera, Cladophialophora bantiana, Dactylaria constricta, Fusarium solani, Paecilomyces lilacinus, Scedosporium prolificans, Trichoderma longibrachiatum, and Wangiella dermatitidis for itraconazole, three new triazoles (voriconazole, posaconazole, and ravuconazole), and amphotericin B. MICs and minimum fungicidal concentrations (MFCs) were determined in each center by using four media (standard RPMI-1640 [RPMI], RPMI with 2% dextrose [RPMI-2%], antibiotic medium 3 [M3], and M3 with 2% dextrose [M3-2%]) and two criteria of MIC determination (complete growth inhibition [MICs-0] and prominent growth inhibition [MICs-2]) at 24, 48 and 72 h. MFCs were defined as the lowest drug concentrations that yielded <3 colonies (approximately 99 to 99.5% killing activity). The reproducibility (within three wells) was higher among MICs-0 (93 to 99%) with either RPMI or M3 media than among all MICs-2 (86 to 95%) for the five agents at 48 to 72 h. The agreement for MFCs was lower (86 to 94%). Based on interlaboratory agreement, the optimal testing conditions were RPMI broth, 48 to 72 h of incubation and 100% growth inhibition (MIC-0); MFCs can be obtained after MIC determination with the above optimal testing parameters. These results warrant consideration for inclusion in the future version of the NCCLS M38 document. However, the role of these in vitro values as predictors of clinical outcome remains to be established in clinical trials.

Testing conditions for determination of minimum fungicidal concentrations of new and established antifungal agents for Aspergillus spp.: NCCLS collaborative study

Standard conditions are not available for evaluating the minimum fungicidal concentrations (MFCs) of antifungal agents. This multicenter collaborative study investigated the reproducibility in three laboratories of itraconazole, posaconazole, ravuconazole, voriconazole, and amphotericin B MFCs for 15 selected isolates of Aspergillus spp. After MIC determinations for the 15 isolates in each center by the NCCLS M38-A broth microdilution method with four media, standard RPMI 1640 (RPMI), RPMI with 2% dextrose, antibiotic medium 3 (M3), and M3 with 2% dextrose, MFCs were determined for each isolate-medium-drug combination. MFCs were defined as the lowest drug dilutions that yielded <3 colonies (approximately 99 to 99.5% killing activity). The highest reproducibility (96 to 100%) was for amphotericin B MFCs with the four media. Although reproducibility was more variable and medium dependent for the azoles (91 to 98%), agreement was good to excellent for itraconazole, ravuconazole, and voriconazole MFCs with RPMI and M3 (93 to 98%). For posaconazole, the agreement was higher with M3 media (91 to 96%) than with RPMI media (91%). These data extend the refinement of testing guidelines for susceptibility testing of Aspergillus spp. and warrant consideration for introduction into future versions of the M38 document. The role of the MFC under these standardized testing conditions as a predictor of clinical outcome needs to be established in clinical trials.

Comparison of the Etest and the sensititre colorimetric methods with the NCCLS proposed standard for antifungal susceptibility testing of Aspergillus species

The susceptibilities of 25 clinical isolates of Aspergillus fumigatus, A. flavus, A. terreus, A. nidulans, and A. ustus to itraconazole and amphotericin B were determined by an agar diffusion-dilution method (the Etest method) and a colorimetric broth microdilution method (the Sensititre method); and the results were compared with those obtained by the NCCLS proposed standard M-38P method for antifungal susceptibility testing of filamentous fungi. Various MIC endpoints for the three methods were determined visually by four different observers in three blinded experiments, and the reproducibilities among the observers (interobserver agreement) and among the replicates (interexperimental agreement) as well as the levels of agreement between the NCCLS, the Etest, and the Sensititre methods were calculated. High levels of reproducibility (within 1 twofold dilution) were found for the NCCLS method (>95%) with the MIC-0 endpoint (complete inhibition of growth) for both drugs and with the MIC-1 endpoint (slight growth) for itraconazole and for the Sensititre method (>90%) with all MIC endpoints, although for the latter the interexperimental agreement for itraconazole was comparatively lower (83 to 93%). The Etest method was less reproducible (67 to 87%) for both drugs. Using the recommended MIC endpoints, high levels of agreement (within one twofold dilution) between the NCCLS and the Sensititre methods for all species were found for amphotericin B (>77%) but not for itraconazole (<66%), for which the MICs by the Sensititre method were up to 3 twofold dilutions lower than the corresponding MICs by the NCCLS method. The use of the first blue well as an endpoint for the Sensititre method and 48 h of incubation improved the levels of agreement with the NCCLS method. Low levels of agreement between the NCCLS and the Etest methods using the recommended MIC endpoints were found for most species, especially after 48 h of incubation (<50%), when the MICs obtained by the Etest method were up to 9 twofold dilutions higher than the corresponding MICs obtained by the NCCLS method. Relatively better agreement was found after 24 h, although it was species dependent, with the highest levels of agreement (>82%) found for A. terreus and A. ustus for amphotericin B and A. fumigatus for both drugs. Overall, better agreement was found when MIC-0 was used as the MIC endpoint for the NCCLS method for both drugs and when the MICs by the Etest method were determined after 48 h of incubation for itraconazole and after 24 h of incubation for amphotericin B.

Increased expression of a novel Aspergillus fumigatus ABC transporter gene, atrF, in the presence of itraconazole in an itraconazole resistant clinical isolate

Aspergillus fumigatus is the most frequent causative agent of invasive aspergillosis. Itraconazole became available in 1990 to treat invasive aspergillosis, but instances of resistance have now been described. Drug efflux was a proposed mechanism in one itraconazole resistant clinical isolate (AF72) which accumulates low levels of the drug. Drug efflux in fungi can be mediated by ATP-binding cassette transporter (ABCT) genes, such as CDR1 in Candida albicans. Using a probe derived from CDR1, a gene, atrF, was cloned from A. fumigatus. The atrF gene product (AtrF) is 1547 amino acids long and has characteristic multidrug resistance motifs. Dot blot analysis revealed that AF72 has approximately 5-fold higher levels of atrF mRNA than susceptible isolates AF10 and H06-03 in cultures with sub-minimum inhibitory concentration (sub-MIC) levels of itraconazole. atrF is the first ABCT gene cloned from A. fumigatus, whose overexpression is correlated with itraconazole resistance.

Nationwide survey of in vitro activities of itraconazole and voriconazole against clinical Aspergillus fumigatus isolates cultured between 1945 and 1998

The isolates in a collection of 170 Aspergillus fumigatus isolates recovered from 114 patients and 21 different medical centers in The Netherlands over a period of 53 years were tested for the presence of resistance to itraconazole and voriconazole according to the guidelines of NCCLS document M38-P and by the E-test. Three isolates were highly resistant to itraconazole, and voriconazole MICs were low for all isolates.

Mechanisms of fungal resistance: an overview

The increased use of antifungal agents in recent years has resulted in the development of resistance to these drugs. The significant clinical implication of resistance has led to heightened interest in the study of antifungal resistance from different angles. In this article we discuss antifungal susceptibility testing, the mode of action of antifungals and mechanisms of resistance. Antifungals are grouped into five groups on the basis of their site of action: azoles, which inhibit the synthesis of ergosterol (the main fungal sterol); polyenes, which bind to fungal membrane sterol, resulting in the formation of aqueous pores through which essential cytoplasmic materials leak out; allylamines, which block ergosterol biosynthesis, leading to accumulation of squalene (which is toxic to the cells); candins (inhibitors of the fungal cell wall), which function by inhibiting the synthesis of beta 1,3-glucan (the major structural polymer of the cell wall); and flucytosine, which inhibits macromolecular synthesis. Different mechanisms contribute to the resistance of antifungal agents. These mechanisms include modification of ERG11 gene at the molecular level (gene mutation, conversion and overexpression), over expression of specific drug efflux pumps, alteration in sterol biosynthesis, and reduction in the intracellular concentration of target enzymes. Approaches to prevent and control the emergence of antifungal resistance include prudent use of antifungals, treatment with the appropriate antifungal and conducting surveillance studies to determine the frequency of resistance.

Method for measuring postantifungal effect in Aspergillus species

An in vitro method for determination of postantifungal effect (PAFE) in molds was developed by using three isolates each of Aspergillus fumigatus, A. flavus, A. terreus, A. nidulans, and A. ustus. MICs of amphotericin B and itraconazole were determined by using National Committee for Clinical Laboratory Standards guidelines (M38-P). The inoculum was prepared in RPMI 1640 broth buffered with MOPS (morpholinepropanesulfonic acid) at pH 7.0, and conidia were exposed to amphotericin B and itraconazole at concentrations of 4, 1, and 0.25 times the MIC, each for 4, 2, and 1 h at 37 degrees C. The same procedure was followed for controls with drug-free medium. Following exposure, the conidia were washed three times in saline and the numbers of CFU per milliliter were determined. Exposed and control conidia were then inoculated into microtitration plates and incubated at 37 degrees C for 48 h in a spectrophotometer reader. The optical density (OD) was measured automatically at 10-min intervals, resulting in growth curves. PAFE was quantified by comparing three arbitrary points in the control growth curve, the first increase of OD and the points when 20 and 50% of the maximal growth were reached, with the growth curve of drug-exposed conidia. Amphotericin B induced PAFE in A. fumigatus at four times the MIC after 2 and 4 h of exposure ranging from 1.83 to 6.00 h and 9.33 to 10.80 h, respectively. Significantly shorter PAFEs or lack of PAFE was observed for A. terreus, A. ustus, and A. nidulans. Itraconazole did not induce measurable PAFE in the Aspergillus isolates at any concentration or exposure time tested. Further studies are warranted to investigate the implications of PAFE in relation to clinical efficacy and dosing frequency.

E-test method for testing susceptibilities of Aspergillus spp. to the new triazoles voriconazole and posaconazole and to established antifungal agents: comparison with NCCLS broth microdilution method

NCCLS document M38-P describes standard parameters for testing the fungistatic activities (MICs) of established agents against filamentous fungi (molds). This study evaluated the in vitro susceptibilities of 15 Aspergillus flavus isolates, 62 A. fumigatus isolates, and 10 isolates each of A. niger, A. nidulans, and A. terreus to voriconazole, posaconazole, itraconazole, and amphotericin B by the E-test and NCCLS M38-P microdilution methods. The agreement (within 3 dilutions) between methods for voriconazole was independent of the E-test incubation time (93.3 to 100% for four of five species at both incubation times). In contrast, with amphotericin B, itraconazole, and posaconazole, E-test results were more dependent on the incubation time for certain species. For A. fumigatus, posaconazole E-test MICs had better concordance with reference values after 48 h (95.2%) than after 24 h (90%), while the highest agreement for itraconazole MICs was after 24 h (90.3 versus 74.2%) of incubation. Better agreement between the methods was also obtained with 24-h E-test amphotericin B MICs for A. flavus (73.3 versus 26.7%) and A. fumigatus (96.7 versus 64.5%). E-test MICs of the four agents had the lowest percentages of agreement with reference values for A. nidulans (60 to 80%). For isolates for which high MICs were obtained for the four agents by the reference method, high MICs were also obtained by E-test at both 24 and 48 h. The utility of in vitro results of either the E-test or the NCCLS broth microdilution (M38-P) method for Aspergillus spp. needs to be established in clinical trials.

Effect of medium composition on static and cidal activity of amphotericin B, itraconazole, voriconazole, posaconazole and terbinafine against Aspergillus fumigatus: a multicenter study

The effect of the medium composition on the fungistatic (MIC) and fungicidal (MLC) activity of amphotericin B, itraconazole, voriconazole, posaconazole and terbinafine against four Aspergillus fumigatus strains has been investigated by four European laboratories. MICs were determined by broth microdilution, using RPMI 1640 and Antibiotic Medium 3 (AM3), three times in three independent determinations by the four laboratories. MLCs were determined for the three independent determinations by the four laboratories, subculturing 100 microl from each well showing no visible growth after 48 hours. Except for a 2-dilution difference observed in three cases, no differences were observed between MICs determined on the two media. In contrast, a 3- to 6-dilution discrepancy between the MLCs was observed for the azoles. Endpoints on RPMI were higher than those on AM3. A 1-2 dilution difference was noted between both the endpoints of amphotericin B and of terbinafine. The highest inter- and intra-laboratory agreements were reached on AM3. The azoles showed a medium-dependent fungicidal activity.

Antifungal drug resistance of pathogenic fungi

Pathogenic fungi have many complex mechanisms of resistance to antifungal drugs. Information about the clinical, cellular, and molecular factors contributing to antifungal-drug resistance continues to accumulate. We critically review the diagnosis, epidemiology, and mechanisms of antifungal drug resistance of pathogenic fungi. Better understanding of this resistance should assist in developing better detection strategies for preventing and treating refractory mycoses in the future.

Antifungal drug resistance: does it matter?

The objectives of this review are: to review the modes of action of currently available antifungal drugs; to define drug resistance and discuss the mechanisms by which fungi can develop resistance to antifungal drugs; to consider the epidemiological and host factors that contribute to the outcome of antifungal therapy and whether the available in vitro susceptibility test methods can reliably predict clinical response; and to assess the overall relevance of drug resistance to the outcome of fungal infections. The incidence of antifungal drug resistance among pathogens causing invasive fungal infections appears to be increasing. In the case of Candida spp., this may in part be a consequence of selective pressure brought about by more intensive antifungal use leading to a 'pathogen shift'. Non-albicans Candida spp. are more likely to demonstrate reduced susceptibility to fluconazole compared to C. albicans. Susceptibility breakpoints developed by the National Committee for Clinical Laboratory Standards to test azoles and flucytosine against Candida spp. are helpful in guiding therapy. Antifungal drug resistance in yeasts is of clinical importance. Increasingly reliable methods of in vitro susceptibility testing can help predict clinical response to therapy, but other considerations, including host- and drug-related factors, can also have an important bearing on the ultimate outcome of treatment.

Quantitative analysis of the relative transcript levels of ABC transporter Atr genes in Aspergillus nidulans by real-time reverse transcription-PCR assay

The development of assays for quantitative analysis of the relative transcript levels of ABC transporter genes by real-time reverse transcription-PCR (RT-PCR) might provide important information about multidrug resistance in filamentous fungi. Here, we evaluate the potential of real-time RT-PCR to quantify the relative transcript levels of ABC transporter Atr genes from Aspergillus nidulans. The AtrA to AtrD genes showed different and higher levels in the presence of structurally unrelated drugs, such as camptothecin, imazalil, itraconazole, hygromycin, and 4-nitroquinoline oxide. We also verified the relative transcript levels of the Atr genes in the A. nidulans imazalil-resistant mutants. These genes displayed a very complex pattern in different ima genetic backgrounds. The imaB mutant has higher basal transcript levels of AtrB and -D than those of the wild-type strain. The levels of these two genes are comparable when the imaB mutant is grown in the presence and absence of imazalil. The imaC, -D, and -H mutants have higher basal levels of AtrA than that of the wild type. The same behavior is observed for the relative transcript levels of AtrB in the imaG mutant background.

Azole cross-resistance in Aspergillus fumigatus

We susceptibility tested 17 clinical isolates of Aspergillus fumigatus, for most of which MICs of itraconazole were elevated (MIC at which 50% of the isolates tested are inhibited, 16 microg/ml), against itraconazole, posaconazole, ravuconazole, and voriconazole. Posaconazole was the most active against itraconazole-susceptible isolates. A complex pattern of cross-resistance and hypersusceptibility was seen with voriconazole and ravuconazole, suggesting marked differences in activity and mechanisms of resistance.

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.

Antifungal susceptibility testing. New technology and clinical applications

The state of the art for susceptibility testing of yeasts is comparable with that of bacteria. Standardized methods for performing antifungal susceptibility testing are reproducible, accurate, and available in clinical laboratories. The development of quality control limits and interpretive criteria for a limited number of antifungal agents provides a basis for the application of this testing in the clinical laboratory. A proficiency testing program is available as a quality assurance measure for laboratories and has documented steady improvement among laboratories using the NCCLS method. As with antibacterial agents, surveillance programs are now in place using reference quality testing methods to monitor antifungal resistance trends on a global scale. It is clear that antifungal susceptibility testing can predict outcome in several clinical situations. Susceptibility testing is most helpful in dealing with infection caused by non-albicans species of Candida, and susceptibility testing of azoles is increasingly important in the management of candidiasis in critically ill patients. Susceptibility testing also has been standardized for filamentous fungi that cause invasive infections. Studies are ongoing to further refine this approach and evaluate the in vivo correlation with the in vitro data for molds. Future efforts must be directed toward establishing and validating interpretive break-points for licensed antifungals such as amphotericin B, and for new antifungals that are not yet licensed. Finally, procedures must be optimized for testing non-Candida yeasts (e.g., C. neoformans) and molds.

Aspergillus: rising frequency of clinical isolation and continued susceptibility to antifungal agents, 1994-1999

We investigated the frequency of clinical isolation and the in vitro susceptibility to antifungal agents of Aspergillus species obtained from patients at the Detroit Medical Center from January 1994 to December 1999. During this period, 593 clinical isolates of Aspergillus species [406 A. fumigatus, 68%; 82 A. niger, 14%; 42 A. flavus, 7%; 63 Aspergillus spp., 11%] were recovered from hospitalized patients. From January 1996 to December 1999, approximately 2.5-4.5 fold yearly increase of the number of aspergillus isolates occurred compared to that of 1994. Conidial suspensions from clinical isolates were prepared and their in vitro susceptibility to amphotericin B and three azoles were determined. All four agents examined were extremely active. The minimum inhibitory concentrations (MIC(90)) (microg/mL) of amphotericin B, itraconazole, voriconazole and posaconazole for A. fumigatus (n = 406) were 0.5, 1.0, 0.5 and 0.25. Similar values were noted for non-A. fumigatus isolates. A year-to-year comparison of the MIC(90) of the four agents for A. fumigatus and non-A. fumigatus isolates over the 6-year study period showed no significant differences. Our study showed a steady increase in the frequency of clinical isolation of Aspergillus species; and the organism has remained susceptible to amphotericin B/triazoles without any change in susceptibility levels during the 6-year study period.

Antifungal susceptibility testing: practical aspects and current challenges

Development of standardized antifungal susceptibility testing methods has been the focus of intensive research for the last 15 years. Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now available. The development of these methods provides researchers not only with standardized methods for testing but also with an understanding of the variables that affect interlaboratory reproducibility. With this knowledge, we have now moved into the phase of (i) demonstrating the clinical value (or lack thereof) of standardized methods, (ii) developing modifications to these reference methods that address specific problems, and (iii) developing reliable commercial test kits. Clinically relevant testing is now available for selected fungi and drugs: Candida spp. against fluconazole, itraconazole, flucytosine, and (perhaps) amphotericin B; Cryptococcus neoformans against (perhaps) fluconazole and amphotericin B; and Aspergillus spp. against (perhaps) itraconazole. Expanding the range of useful testing procedures is the current focus of research in this area.

Optimal susceptibility testing conditions for detection of azole resistance in Aspergillus spp.: NCCLS collaborative evaluation. National Committee for Clinical Laboratory Standards

The most important role of susceptibility testing is to identify potentially resistant isolates for the agent being evaluated. Standard testing guidelines recently have been proposed for antifungal susceptibility testing of filamentous fungi (molds). This collaborative (eight centers) study evaluated further newly proposed guidelines (NCCLS, proposed standard M38-P, 1998) and other testing conditions for antifungal susceptibility testing of Aspergillus spp. to itraconazole and three new triazoles, posaconazole (SCH56592), ravuconazole (BMS-207147), and voriconazole. MICs of itraconazole, posaconazole, ravuconazole, and voriconazole for 15 selected isolates of three species of Aspergillus (A. fumigatus, A. flavus, and A. terreus) with well documented in vitro, clinical, or animal data were determined in each center by using four medium formulations (standard RPMI-1640 [RPMI], RPMI with 2% dextrose, antibiotic medium 3 [M3], and M3 with 2% dextrose) and two criteria of MIC determination (complete [MIC-0s] and prominent [MIC-2s] growth inhibition) at 24, 48, and 72 h. The highest reproducibility (92 to 99%) was seen with the standard RPMI and M3 media. Moreover, the distinction between itraconazole-resistant (MICs of >8 microg/ml for clinically resistant strains) and -susceptible (MICs of 0.03 to 1 microg/ml) isolates, as well as between a voriconazole-resistant laboratory mutant and other isolates (voriconazole MICs of 2 to >8 versus 0.12 to 2 microg/ml), was more consistently evident with the standard RPMI medium and when MIC-0s were determined at 48 h. These results provide further refinement of the testing guidelines for susceptibility testing of Aspergillus spp. and warrant consideration for inclusion in the future NCCLS document M38-A.

Sterol composition of itraconazole-resistant and itraconazole-susceptible isolates of Aspergillus fumigatus

Sterol composition of four clinical isolates of Aspergillus fumigatus resistant to itraconazole was determined by gas chromatography – mass spectrometry and compared with that of four susceptible strains. For all strains, the major sterol was ergosterol. Sterol compositions were qualitatively and quantitatively similar for the resistant and susceptible strains. These results suggest that itraconazole resistance is not related, for the strains studied, to alterations in the ergosterol synthesis pathway.Key words: Aspergillus fumigatus, itraconazole resistance, sterol composition.

Antifungal prophylaxis in hematopoietic stem cell transplant recipients

Infections remain a major complication of hematopoietic stem cell transplantation, with recent trends indicating that fungal pathogens have become one of the most common causes of death. Attention has turned to the use of prophylactic antifungal medications to prevent infection with both Candida and Aspergillus species. Recent studies, which are reviewed within, indicate success in preventing infections caused by azole-susceptible Candida species, accompanied by improved transplant-related mortality rates in high-risk patients. Further studies are necessary to develop strategies to prevent infection with Aspergillus species.

Identification of two different 14-alpha sterol demethylase-related genes (cyp51A and cyp51B) in Aspergillus fumigatus and other Aspergillus species

Two cyp51-related genes (cyp51A and cyp51B) encoding 14-alpha sterol demethylase-like enzymes were identified in the opportunistic human pathogen Aspergillus fumigatus. PCR amplification using degenerate oligonucleotides based on conserved areas of cytochrome P450 demethylases of other filamentous fungi and yeasts allowed the cloning and sequencing of two different homologue genes in A. fumigatus. Southern analysis confirmed that both genes hybridized to distinct genomic loci and that both are represented as single copies in the genome. Comparison of the deduced Cyp51A and Cyp51B proteins with the CYP51 proteins from Penicillium italicum, Aspergillus nidulans, Erysiphe graminis, Uncinula necator, Botrytis cinerea, Ustilago maydis, Cryptococcus neoformans, Candida albicans, Saccharomyces cerevisiae, Candida tropicalis, and Candida glabrata showed that the percentages of identity of the amino acid sequences (range, 40 to 70%) were high enough to consider Cyp51A and Cyp51B to be members of the fungal CYP51 family. Fragments from both genes were also cloned from other Aspergillus spp. (A. flavus, A. nidulans, and A. terreus). Phylogenetic analysis showed that, at least in the most pathogenic species of Aspergillus, there are two fungal CYP51 proteins. This is the first report of the existence of two homologue genes coding for 14-alpha sterol demethylase in the fungal kingdom. This finding could provide insights into the azole resistance mechanisms operating in fungi. The primers used here may be useful molecular tools for facilitating the cloning of novel 14-alpha sterol demethylase genes in other filamentous fungi.

Aspergillus fumigatus CYP51 sequence: potential basis for fluconazole resistance

We have cloned and sequenced the Aspergillus fumigatus CYP51 gene which encodes the target of azole antifungal agents, namely cytochrome P450 sterol 14alpha-demethylase. Since A. fumigatus is intrinsically resistant to the widely used azole fluconazole, we compared its predicted CYP51 sequence to the CYP51 sequences from fluconazole-susceptible and resistant Candida albicans. This analysis generated specific hypotheses regarding the basis for A. fumigatus fluconazole resistance; in particular, A. fumigatus residue Ile301 corresponds to C. albicans residue Thr315 which is mutated to Ala in resistant strains and is proposed to hydrogen bond with the sterol substrate.

Susceptibility testing of Aspergillus flavus: inoculum dependence with itraconazole and lack of correlation between susceptibility to amphotericin B in vitro and outcome in vivo

We have attempted to validate in Aspergillus flavus the main in vitro methodologies that have been used to detect resistance in Aspergillus fumigatus. We developed a murine model with two A. flavus isolates, one that was apparently resistant in vitro to amphotericin B (AFL5) and another that was resistant to itraconazole (AFL8). No correlation was found for amphotericin B in AFL5, since the in vivo response was compatible with a susceptible isolate. Modification of the in vitro susceptibility test methodology for amphotericin B was unsuccessful. Although AFL8 was apparently resistant to itraconazole in vitro, it was found to be susceptible in vivo. Additional in vitro work has detected weaknesses in the in vitro susceptibility methodology validated for A. fumigatus when applied to A. flavus. The principal problems are that changes in the inoculum have a large effect on the MICs of itraconazole for some A. flavus strains and that a trailing end point and spore sediment often appear when an inoculum with a higher colony count is used. We propose a modified method using a final inoculum of 2.5 x 10(4) CFU per ml of RPMI 1640 medium with 2% glucose buffered to pH 7.0 in a microtiter format, incubated for 48 h with no growth end point. Validation of this methodology requires one or more itraconazole-resistant A. flavus isolates, which have yet to be identified.

Clinical experience with itraconazole in systemic fungal infections

The broad spectrum antifungal itraconazole is an effective and well tolerated agent for the prophylaxis and treatment of systemic fungal infections. The recent development of an itraconazole oral solution and an intravenous itraconazole solution has increased the options for the use of this drug and increased the oral bioavailability in a variety of at-risk patients. Reliable absorption of the itraconazole oral solution has been demonstrated in patients with HIV infection, neutropenic patients with haematological malignancy, bone marrow transplant recipients and neutropenic children. In clinical trials, itraconazole oral solution (5 mg/kg/day) was more effective at preventing systemic fungal infection in patients with haematological malignancy than placebo, fluconazole suspension (100 mg/day) or oral amphotericin-B (2 g/kg/day) and was highly effective at preventing fungal infections in liver transplant recipients. There were no unexpected adverse events with the itraconazole oral solution in any of these trials. In addition, intravenous itraconazole solution is at least as effective as intravenous amphotericin-B in the empirical treatment of neutropenic patients with systemic fungal infections, and drug-related adverse events are more frequent in patients treated with amphotericin-B. A large proportion of patients with confirmed aspergillosis also respond to treatment with intravenous itraconazole followed by oral itraconazole. The new formulations of itraconazole are therefore effective agents for prophylaxis and treatment of most systemic fungal infections in patients with haematological malignancy.

Comparison of the E-test with the NCCLS M38-P method for antifungal susceptibility testing of common and emerging pathogenic filamentous fungi

The National Committee for Clinical Laboratory Standards (NCCLS) M38-P method describes standard parameters for testing the fungistatic antifungal activities (MICs) of established agents against filamentous fungi (molds). The present study evaluated the in vitro fungistatic activities of itraconazole and amphotericin B by the E-test and the NCCLS M38-P microdilution method against 186 common and emerging pathogenic molds (123 isolates of Aspergillus spp. [five species], 16 isolates of Fusarium spp. [two species], 4 Paecilomyces lilacinus isolates, 5 Rhizopus arrhizus isolates, 15 Scedosporium spp., 18 dematiaceous fungi, and 5 Trichoderma longibrachiatum isolates). The agreement between the methods for amphotericin B MICs ranged from 70% for Fusarium solani to > or =90% for most of the other species after the first reading; agreement was dependent on both the incubation time and the species being evaluated. Major discrepancies between the amphotericin B MICs determined by the E-test and the NCCLS M38-P method were demonstrated for three of the five species of Aspergillus tested and the two species of Fusarium tested. This discrepancy was more marked after 48 h of incubation; the geometric mean MICs determined by the E-test increased between 24 and 48 h from between 1.39 and 3.3 microg/ml to between 5.2 and >8 microg/ml for Aspergillus flavus, Aspergillus fumigatus, and Aspergillus nidulans. The agreement between the itraconazole MICs determined by the E-test and the NCCLS M38-P method ranged from 83.3% for A. nidulans to > or =90% for all the other species tested; the overall agreement was higher (92.7%) than that for amphotericin B (87.9%). The agreement was less dependent on the incubation time. Clinical trials need to be conducted to establish the role of the results of either the E-test or the NCCLS M38-P method in vitro for molds with the two agents as predictors of clinical outcome.

In vitro fungicidal activities of voriconazole, itraconazole, and amphotericin B against opportunistic moniliaceous and dematiaceous fungi

The NCCLS proposed standard M38-P describes standard parameters for testing the fungistatic antifungal activities (MICs) of established agents against filamentous fungi (molds); however, standard conditions are not available for testing their fungicidal activities (minimum fungicidal or lethal concentrations [MFCs]). This study evaluated the in vitro fungistatic and fungicidal activities of voriconazole, itraconazole, and amphotericin B against 260 common and emerging molds (174 Aspergillus sp. isolates [five species], 23 Fusarium sp. isolates [three species], 6 Paecilomyces lilacinus isolates, 6 Rhizopus arrhizus isolates, 23 Scedosporium sp. isolates, 23 dematiaceous fungi, and 5 Trichoderma longibrachiatum isolates). MICs were determined by following the NCCLS M38-P broth microdilution method. MFCs were the lowest drug dilutions that resulted in fewer than three colonies. Voriconazole showed similar or better fungicidal activity (MFC at which 90% of isolates tested are killed [MFC(90)], 1 to 2 microg/ml) than the reference agents for Aspergillus spp. with the exception of Aspergillus terreus (MFC(90) of voriconazole and amphotericin B, >8 microg/ml). The voriconazole geometric mean (G mean) MFC for Scedosporium apiospermum was lower (2.52 microg/ml) than those of the other two agents (5.75 to 7.5 microg/ml). In contrast, amphotericin B and itraconazole G mean MFCs for R. arrhizus were 2.1 to 2.2 microg/ml, but that for voriconazole was >8 microg/ml. Little or no fungicidal activity was shown for Fusarium spp. (2 to >8 microg/ml) and Scedosporium prolificans (>8 microg/ml) by the three agents, but voriconazole had some activity against P. lilacinus and T. longibrachiatum (G mean MFCs, 1.8 and 4 microg/ml, respectively). The fungicidal activity of the three agents was similar (G mean MFC, 1.83 to 2.36 microg/ml) for the dematiaceous fungi with the exception of the azole MFCs (>8 microg/ml) for some Bipolaris spicifera and Dactylaria constricta var. gallopava. These data extend and corroborate the available fungicidal results for the three agents. The role of the MFC as a predictor of clinical outcome needs to be established in clinical trials by following standardized testing conditions for determination of these in vitro values.

Occurrence of itraconazole-tolerant micromycetes in the soil and food products

Unexpected pathogens from the environment represent considerable risk for humans with impaired health. We examined the occurrence of itraconazole tolerant micromycetes in soil and in maize products. Five concentrations of itraconazole (2.5-12.5 micrograms/mL) selected according to known treatment schedules for human patients were incorporated into Sabouraud agar with chloramphenicol and Rose Bengal and diluted samples were inoculated onto the agar surface. After 7-d growth at 22 degrees C colonies of Alternaria sp., Aspergillus clavatus, A. glaucus group, A. flavus, A. fumigatus, A. niger group, A. ochraceus group, A. ochraceus, Chaetomium sp., Cladosporium cladosporioides, Cylindrocarpon sp., Doratomyces sp., Fusarium sp., F. moniliforme, F. oxysporum, F. solani, F. subglutinans, Marianaea elegans, Mortierella sp., Mucor sp., Myrothecium sp., Penicillium sp., Rhizopus sp., Scopulariopsis brevicaulis, Sepedonium sp., Stachybotrys chartarum, Stemphylium sp., Torula humicola and Trichoderma viride were isolated.