In vitro antifungal susceptibilities of Trichosporon species

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

In vitro interactions of approved and novel drugs against Paecilomyces spp

We have evaluated the in vitro activity of 15 combinations of antifungal drugs (amphotericin B, itraconazole, voriconazole, albaconazole, ravuconazole, terbinafine, and micafungin) against four isolates of Paecilomyces variotii and three of P. lilacinus. The interaction of terbinafine with the four azoles was synergistic for 53% of the combinations, while the interactions of both amphotericin B and micafungin with the rest of antifungal agents were mainly indifferent.     

In vitro activities of ravuconazole and voriconazole compared with those of four approved systemic antifungal agents against 6,970 clinical isolates of Candida spp

The in vitro activities of ravuconazole and voriconazole were compared with those of amphotericin B, flucytosine (5FC), itraconazole, and fluconazole against 6,970 isolates of Candida spp. obtained from over 200 medical centers worldwide. Both ravuconazole and voriconazole were very active against all Candida spp. (MIC at which 90% of the isolates tested are inhibited [MIC(90)], 0.25 microg/ml; 98% of MICs were < or 1 microg/ml); however, a decrease in the activities of both of these agents was noted among isolates that were susceptible-dose dependent (fluconazole MIC, 16 to 32 microg/ml) and resistant (MIC, > or = 64 microg/ml) to fluconazole. Candida albicans was the most susceptible species (MIC(90) of both ravuconazole and voriconazole, 0.03 microg/ml), and C. glabrata was the least susceptible species (MIC(90), 1 to 2 microg/ml). Ravuconazole and voriconazole were each more active in vitro than amphotericin B, 5FC, itraconazole, and fluconazole against all Candida spp. and were the only agents with good in vitro activity against C. krusei. These results provide further evidence for the spectrum and potency of ravuconazole and voriconazole against a large and geographically diverse collection of Candida spp.     

Antifungal activities of posaconazole, ravuconazole, and voriconazole compared to those of itraconazole and amphotericin B against 239 clinical isolates of Aspergillus spp. and other filamentous fungi: report from SENTRY Antimicrobial Surveillance Program, 2000

Posaconazole, ravuconazole, and voriconazole are new triazole derivatives that possess potent, broad-spectrum antifungal activity. We evaluated the in vitro activity of these investigational triazoles compared with that of itraconazole and amphotericin B against 239 clinical isolates of filamentous fungi from the SENTRY Program, including Aspergillus spp. (198 isolates), Fusarium spp. (7 isolates), Penicillium spp. (19 isolates), Rhizopus spp. (4 isolates), Mucor spp. (2 isolates), and miscellaneous species (9 isolates). The isolates were obtained from 16 different medical centers in the United States and Canada between January and December 2000. In vitro susceptibility testing was performed using the microdilution broth method outlined in the National Committee for Clinical Laboratory Standards M38-P document. Overall, posaconazole was the most active compound, inhibiting 94% of isolates at a MIC of < or = 1 microg/ml, followed by voriconazole (91%), amphotericin B (89%), ravuconazole (88%), and itraconazole (70%). All three new triazoles demonstrated excellent activity (MIC, < or = 1 microg/ml) against Aspergillus spp. (114 Aspergillus fumigatus, 22 Aspergillus niger, 13 Aspergillus flavus, 9 Aspergillus versicolor, 8 Aspergillus terreus, and 32 Aspergillus spp.): posaconazole (98%), voriconazole (98%), ravuconazole (92%), amphotericin B (89%), and itraconazole (72%). None of the triazoles were active against Fusarium spp. (MIC at which 50% of the isolates tested were inhibited [MIC(50)], >8 microg/ml) or Mucor spp. (MIC(50), >8 microg/ml). Posaconazole and ravuconazole were more active than voriconazole against Rhizopus spp. (MIC(50), 1 to 2 microg/ml versus >8 microg/ml, respectively). Based on these results, all three new triazoles exhibited promising activity against Aspergillus spp. and other less commonly encountered isolates of filamentous fungi. The clinical value of these in vitro data remains to be seen, and in vitro-in vivo correlation is needed for both new and established antifungal agents. Surveillance efforts should be expanded in order to monitor the spectrum of filamentous fungal pathogens and their in vitro susceptibility as these new antifungal agents are introduced into clinical use.     

Differential activity of triazoles in two-drug combinations with the echinocandin caspofungin against Aspergillus fumigatus

OBJECTIVES: We investigated the in vitro activity of various triazoles in two-drug combinations with the echinocandin caspofungin against clinical isolates of Aspergillus fumigatus.Method: Conidial suspensions were prepared from 20 clinical isolates of A. fumigatus highly susceptible to itraconazole, voriconazole, posaconazole and ravuconazole (MIC-0 range 0.125-1 mg/L), and caspofungin (MIC-0 range 32-64 mg/L). The in vitro susceptibility of A. fumigatus to two-drug combinations of itraconazole, voriconazole, posaconazole and ravuconazole with caspofungin was evaluated by the fractional inhibitory concentration index (FICI) method. RESULTS: Two-drug combinations of caspofungin with itraconazole (FICI = 0.49 +/- 0.04) or posaconazole (FICI = 0.32 +/- 0.09) provided synergic interaction. On the other hand, ravuconazole (FICI = 0.61 +/- 0.31) and voriconazole (FICI = 1.61 +/- 0.42) in combination with caspofungin showed no interaction against A. fumigatus. CONCLUSIONS: Our data show that the in vitro antifungal efficacies of combinations of members from two different classes are not always similar and hence are not predictable.     

Head-to-head comparison of the activities of currently available antifungal agents against 3,378 Spanish clinical isolates of yeasts and filamentous fungi

We have compared the activities of posaconazole and other currently available antifungal agents against a collection of 3,378 clinical isolates of yeasts and filamentous fungi. A total of 1,997 clinical isolates of Candida spp., 359 of other yeast species, 697 strains of Aspergillus spp., and 325 nondermatophyte non-Aspergillus spp. were included. The average geometric means of the MICs of agents that were tested against Candida spp. were 0.23 microg/ml for amphotericin B, 0.29 microg/ml for flucytosine, 0.97 microg/ml for fluconazole, 0.07 microg/ml for itraconazole, 0.04 microg/ml for voriconazole, 0.15 microg/ml for caspofungin, and 0.03 microg/ml for posaconazole. Voriconazole and posaconazole were active in vitro against the majority of isolates, with resistance to fluconazole and itraconazole, and against Cryptococcus neoformans and other Basidiomycota yeasts. Posaconazole was the most active of antifungal agents tested against Aspergillus spp., with an average geometric mean of 0.10 microg/ml. It was active against Paecilomyces spp., Penicillium spp., Scedosporium apiospermum, and some black fungi, such as Alternaria spp. Multiresistant filamentous fungi, such as Scedosporium prolificans, Scopulariopsis brevicaulis, and Fusarium solani, were also resistant to voriconazole, caspofungin, and posaconazole. Amphotericin B and posaconazole were found to be active against most of the Mucorales strains tested. Posaconazole and currently available antifungal agents exhibit a potent activity in vitro against the majority of pathogenic fungal species.     

In vitro interaction of micafungin with conventional and new antifungals against clinical isolates of Trichosporon, Sporobolomyces and Rhodotorula

OBJECTIVES: The infections caused by basidiomycetous yeasts are often difficult to resolve. Combined therapy might be useful in those severe cases where a monotherapy was ineffective. The aim of this study was to evaluate the in vitro activity of combinations of micafungin with amphotericin B or fluconazole, itraconazole, voriconazole and ravuconazole against isolates of Trichosporon, Rhodotorula and Sporobolomyces. METHODS: Twenty-seven clinical isolates were tested, i.e. 10 of Trichosporon asahii, two of Trichosporon mucoides, five of Sporobolomyces salmonicolor and 10 of Rhodotorula glutinis. Drug interactions were assessed by the chequerboard technique using the NCCLS microdilution method (M27-A2). The fractional inhibitory concentration index (FICI) was used to classify drug interactions. Results were interpreted as follows: synergy (FICI < or =0.5), no interaction (FICI >0.5 and < or =4.0), or antagonism (FICI >4.0). RESULTS: Micafungin combined with amphotericin B showed the highest percentage of synergic interactions (78%) followed by micafungin/ravuconazole and micafungin/itraconazole (48% for each), and micafungin/fluconazole and micafungin/voriconazole (34% for each). Antagonism was not observed in any case. CONCLUSIONS: Some of the combinations tested, especially micafungin/amphotericin B, have potential for the treatment of basidiomycetous yeast infections.     

In vitro activities of posaconazole, fluconazole, itraconazole, voriconazole, and amphotericin B against a large collection of clinically important molds and yeasts

The in vitro activity of the novel triazole antifungal agent posaconazole (Noxafil; SCH 56592) was assessed in 45 laboratories against approximately 19,000 clinically important strains of yeasts and molds. The activity of posaconazole was compared with those of itraconazole, fluconazole, voriconazole, and amphotericin B against subsets of the isolates. Strains were tested utilizing Clinical and Laboratory Standards Institute broth microdilution methods using RPMI 1640 medium (except for amphotericin B, which was frequently tested in antibiotic medium 3). MICs were determined at the recommended endpoints and time intervals. Against all fungi in the database (22,850 MICs), the MIC(50) and MIC(90) values for posaconazole were 0.063 microg/ml and 1 mug/ml, respectively. MIC(90) values against all yeasts (18,351 MICs) and molds (4,499 MICs) were both 1 mug/ml. In comparative studies against subsets of the isolates, posaconazole was more active than, or within 1 dilution of, the comparator drugs itraconazole, fluconazole, voriconazole, and amphotericin B against approximately 7,000 isolates of Candida and Cryptococcus spp. Against all molds (1,702 MICs, including 1,423 MICs for Aspergillus isolates), posaconazole was more active than or equal to the comparator drugs in almost every category. Posaconazole was active against isolates of Candida and Aspergillus spp. that exhibit resistance to fluconazole, voriconazole, and amphotericin B and was much more active than the other triazoles against zygomycetes. Posaconazole exhibited potent antifungal activity against a wide variety of clinically important fungal pathogens and was frequently more active than other azoles and amphotericin B.     

Rates of antifungal resistance among Spanish clinical isolates of Cryptococcus neoformans var. neoformans

OBJECTIVES: Activities in vitro of six antifungal agents were tested against a collection of 317 Cryptococcus neoformans var. neoformans clinical isolates. METHODS: The procedure described in document 7.1 by the European Committee on Antibiotic Susceptibility Testing with minor modifications was employed. RESULTS: Amphotericin B, itraconazole, voriconazole and ravuconazole exhibited a potent activity with geometric mean (GM) MICs under 0.26 mg/L. The GM MIC of flucytosine was 7.33 mg/L and that of fluconazole was 4.16 mg/L. The rates of antifungal resistance were 5.3% for amphotericin B, 0.9% for voriconazole and 3.1% for ravuconazole. Fifteen point eight per cent of strains had itraconazole MICs > or = 1 mg/L, and 46% of strains had flucytosine MICs > or = 8 mg/L. Fluconazole susceptibility (MIC < or = 8 mg/L) stood at 53.4%. CONCLUSIONS: The percentage of fluconazole susceptibility was significantly lower than that in other surveys. Cross-resistance to itraconazole was common (33.8%) but almost the whole collection was susceptible to voriconazole and ravuconazole. These results should be confirmed with prospective and population-based surveillance programmes.     

Comparison of EUCAST and CLSI broth microdilution methods for the susceptibility testing of 10 Systemically active antifungal agents when tested against Candida spp.

The antifungal broth microdilution (BMD) method of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) was compared with Clinical and Laboratory Standards Institute (CLSI) BMD method M27-A3 for amphotericin B, flucytosine, anidulafungin, caspofungin, micafungin, fluconazole, isavuconazole, itraconazole, posaconazole, and voriconazole susceptibility testing of 357 isolates of Candida. The isolates were selected from global surveillance collections to represent both wild-type (WT) and non-WT MIC results for the azoles (12% of fluconazole and voriconazole results were non-WT) and the echinocandins (6% of anidulafungin and micafungin results were non-WT). The study collection included 114 isolates of Candida albicans, 73 of C. glabrata, 76 of C. parapsilosis, 60 of C. tropicalis, and 34 of C. krusei. The overall essential agreement (EA) between EUCAST and CLSI results ranged from 78.9% (posaconazole) to 99.6% (flucytosine). The categorical agreement (CA) between methods and species of Candida was assessed using previously determined CLSI epidemiological cutoff values. The overall CA between methods was 95.0% with 2.5% very major (VM) and major (M) discrepancies. The CA was >93% for all antifungal agents with the exception of caspofungin (84.6%), where 10% of the results were categorized as non-WT by the EUCAST method and WT by the CLSI method. Problem areas with low EA or CA include testing of amphotericin B, anidulafungin, and isavuconazole against C. glabrata, itraconazole, and posaconazole against most species, and caspofungin against C. parapsilosis, C. tropicalis, and C. krusei. We confirm high level EA and CA (>90%) between the 2 methods for testing fluconazole, voriconazole, and micafungin against all 5 species. The results indicate that the EUCAST and CLSI methods produce comparable results for testing the systemically active antifungal agents against the 5 most common species of Candida; however, there are several areas where additional steps toward harmonization are warranted.     

In vitro activities of posaconazole, itraconazole, voriconazole, amphotericin B, and fluconazole against 37 clinical isolates of zygomycetes

In vitro antifungal susceptibility testing results of a new antifungal triazole, posaconazole (POS), were compared to results with amphotericin B (AMB), itraconazole (ITC), voriconazole (VRC), and fluconazole (FLC) against clinical agents of zygomycosis. The MICs of POS at which 50% and 90% of the isolates were inhibited were 0.25 and 4 microg/ml, respectively. POS was significantly more active than VRC and FLC and slightly more active than ITC. The results suggest that POS has significant potential for clinical development against the zygomycetes.     

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.     

In vitro interactions of micafungin with other antifungal drugs against clinical isolates of four species of Cryptococcus

The combination of micafungin (MFG) with amphotericin B (AMB), fluconazole, itraconazole, voriconazole, or ravuconazole was evaluated against 37 strains of four species of Cryptococcus by the checkerboard method. Antagonism was never seen. Synergy was observed for some isolates for each combination and was most frequent with MFG-AMB.     

A comparative study of the in vitro susceptibilities of clinical and laboratory-selected resistant isolates of Aspergillus spp. to amphotericin B, itraconazole, voriconazole and posaconazole (SCH 56592)

We investigated the in vitro susceptibilities of clinical and laboratory-selected Aspergillus spp. to posaconazole, and compared the results with those obtained for amphotericin B, itraconazole and voriconazole. Conidial suspensions from clinical isolates (284 Aspergillus fumigatus, 66 Aspergillus niger, 31 Aspergillus flavus and 43 Aspergillus spp.) and laboratory-selected resistant A. fumigatus isolates (15 resistant to amphotericin B, 25 to itraconazole and 12 to voriconazole) were prepared and their susceptibilities to various antifungal agents determined using a previously described broth macrodilution technique. The geometric mean MICs (mg/L) of posaconazole for A. fumigatus (0.17 +/- 0.11) and non-A. fumigatus aspergilli (0.16 +/- 0.28) were significantly lower (P 0.05) than those for amphotericin B, itraconazole and voriconazole. Amphotericin B-resistant A. fumigatus isolates were as susceptible to posaconazole as the parental strain. Itraconazole- and voriconazole-resistant isolates showed low-level (two- to three-fold increase in MICs) cross-resistance to posaconazole. The minimum fungicidal concentrations (mg/L) of posaconazole for A. fumigatus (n = 58) and non-A. fumigatus aspergilli (n = 40) were 4. 45 +/- 2.70 (range 0.25-8) and 4.14 +/- 3.03 (range 0.5-8), respectively. Time-kill studies showed that the fungicidal activity of posaconazole against A. fumigatus is time- and concentration-dependent (for example, posaconazole 4 mg/L killed >99% of A. fumigatus conidia within 24 h). These results suggest that overall, posaconazole has better activity and a smaller range of MICs for Aspergillus spp., including those with reduced susceptibility to amphotericin B, itraconazole and voriconazole.     

Susceptibility patterns of Candida species recovered from Canadian intensive care units

OBJECTIVE: The objective of this study was to determine the speciation and susceptibility patterns of Candida species recovered from Canadian intensive care units (ICUs) during a 1-day point-prevalence study on fungal colonization/infection in Canadian ICUs. METHODS AND SETTING: Blood, urine, respiratory tract, rectal, and wound fungal cultures were performed for 357 patients present at any time during a single-day 24-hour period in 35 Canadian ICUs. Comparative in vitro activities of amphotericin B, fluconazole, itraconazole, voriconazole, posaconazole, micafungin, anidulafungin, and aminocandin were determined. RESULTS: Four hundred fifteen yeasts (409 Candida species and 6 non-Candida yeasts) were recovered. Almost 50% of the patients were found to have positive respiratory tract or rectal cultures. Candida albicans accounted for 72% of the Candida species isolated, followed by Candida glabrata (16%), Candida tropicalis (5%), Candida parapsilosis (3%), Candida krusei (2%), and other Candida species or nonspeciated isolates (2%). Minimum inhibitory concentrations (milligrams per liter) at which 90% of the strains were inhibited were 0.06 for micafungin as well as anidulafungin, 0.12 for voriconazole, 0.25 for itraconazole, posaconazole, as well as aminocandin, 1 for amphotericin B, and 4 for fluconazole. Only 4% of the isolates were resistant to fluconazole and/or itraconazole. CONCLUSIONS: Candida albicans is the predominant species colonizing Canadian ICU patients. Overall, the triazoles, both older and new compounds, and the echinocandins have excellent in vitro antifungal activities against Candida species recovered from Canadian ICUs patients.     

Activity of newer triazoles against Histoplasma capsulatum from patients with AIDS who failed fluconazole

OBJECTIVES: To determine the activity of newer triazoles against strains of Histoplasma capsulatum resistant to fluconazole. METHODS: Susceptibility testing was performed on 17 paired pre- and post-treatment H. capsulatum isolates from patients with AIDS who failed fluconazole. RESULTS: The median MICs of fluconazole, voriconazole, and posaconazole and ravuconazole for the pre-treatment isolates were 1 mg/L, 0.015 mg/L and <0.007 mg/L, respectively. A 4-fold or greater increase in the MIC of fluconazole and voriconazole was observed in 12 and 7 of the post-treatment isolates, respectively; the median fold increases in MIC were 8 and 2.1, respectively. No MIC increases were observed for posaconazole and ravuconazole. One pair of isolates exhibiting reduced susceptibility was examined in more detail. A single amino acid substitution (at tyrosine 136) was identified in the active site of the CYP51 protein from the post-treatment isolate, which is presumed to be responsible for reduced susceptibility to voriconazole and fluconazole, analogous to recent observations in Candida albicans. CONCLUSIONS: These findings support careful monitoring for relapse in patients receiving voriconazole treatment for histoplasmosis, particularly in those who were previously treated with fluconazole.     

Species-specific antifungal susceptibility patterns of Scedosporium and Pseudallescheria species

Since the separation of Pseudallescheria boydii and P. apiosperma in 2010, limited data on species-specific susceptibility patterns of these and other species of Pseudallescheria and its anamorph Scedosporium have been reported. This study presents the antifungal susceptibility patterns of members affiliated with both entities. Clinical and environmental isolates (n = 332) from a wide range of sources and origins were identified down to species level and tested according to CLSI M38-A2 against eight antifungal compounds. Whereas P. apiosperma (geometric mean MIC/minimal effective concentration [MEC] values of 0.9, 2.4, 7.4, 16.2, 0.2, 0.8, 1.5, and 6.8 μg/ml for voriconazole, posaconazole, isavuconazole, itraconazole, micafungin, anidulafungin, caspofungin, and amphotericin B, respectively) and P. boydii (geometric mean MIC/MEC values of 0.7, 1.3, 5.7, 13.8, 0.5, 1.4, 2.3, and 11.8 μg/ml for voriconazole, posaconazole, isavuconazole, itraconazole, micafungin, anidulafungin, caspofungin, and amphotericin B, respectively) had similar susceptibility patterns, those for S. aurantiacum, S. prolificans, and S. dehoogii were different from each other. Voriconazole was the only drug with significant activity against S. aurantiacum isolates. The MIC distributions of all drugs except voriconazole did not show a normal distribution and often showed two subpopulations, making a species-based prediction of antifungal susceptibility difficult. Therefore, antifungal susceptibility testing of all clinical isolates remains essential for targeted antifungal therapy. Voriconazole was the only compound with low MIC values (MIC(90) of ≤ 2 μg/ml) for P. apiosperma and P. boydii. Micafungin and posaconazole showed moderate activity against the majority of Scedosporium strains.     

Susceptibility testing and molecular classification of Paecilomyces spp

In vitro susceptibility profiles of 58 Paecilomyces clinical isolates are reported. Amphotericin B, itraconazole, and echinocandins showed poor activity against Paecilomyces lilacinus, while the new triazoles were active against it. Paecilomyces variotii exhibited a different susceptibility pattern, being susceptible to most antifungal agents apart from voriconazole and ravuconazole.     

In Vitro Activities of Four Novel Triazoles against Scedosporium spp.

In order to develop new approaches to the treatment of the severe and usually fatal infections caused by Scedosporium spp., the in vitro antifungal activities of four novel triazoles (posaconazole, ravuconazole, voriconazole, and UR-9825) and some current antifungals (amphotericin B, ketoconazole, itraconazole, and nystatin) were determined. The latter group was clearly ineffective against the two species tested. The four new antifungals showed activity against Scedosporium apiospermum, and UR-9825 and voriconazole were active against S. prolificans.     

In vitro activity of isavuconazole against 208 Aspergillus flavus isolates in comparison with 7 other antifungal agents: assessment according to the methodology of the European Committee on Antimicrobial Susceptibility Testing

Aspergillus flavus is the second most common species causing invasive aspergillosis after A. fumigatus. In certain countries like India, Sudan, and Saudi Arabia, A. flavus is most frequently isolated from patients with fungal rhinosinusitis and endophthalmitis. A. flavus exhibit an increased resistance to antifungal agents compared to A. fumigatus. We determined the in vitro activity of isavuconazole, voriconazole, posaconazole, itraconazole, amphotericin B, caspofungin, micafungin, and anidulafungin against 208 isolates of A. flavus by the EUCAST method and compared with the results obtained by the CLSI method. Isavuconazole and voriconazole MICs were ≤2 μg/mL in 99% and 95%, respectively. Posaconazole and itraconazole MICs were ≤0.5 and ≤1 μg/mL, respectively, for all isolates. MICs of amphotericin B were ≥2 μg/mL in 91%; 36% of them exhibited MICs of ≥8 μg/mL. All echinocandins demonstrated good anti-A. flavus activity. The essential agreement of the MIC/MEC results by EUCAST with CLSI broth dilution method assessed at ±2 dilutions was good for itraconazole (97.8%), voriconazole (100%), posaconazole (98.3%), isavuconazole (98.9%), caspofungin (99.4%), and anidulafungin (100%), but poor for amphotericin B (53.5%) and micafungin (79.1%).