In vitro activity of three new triazoles and one echinocandin against Candida bloodstream isolates from cancer patients

The in vitro activities of voriconazole, posaconazole, ravuconazole and micafungin were compared with those of fluconazole, itraconazole, ketoconazole, flucytosine and amphotericin B against 164 candidaemia isolates recovered from cancer patients in two Canadian centres. The MIC(50) results for ravuconazole, voriconazole, posaconazole and micafungin were 0.01, 0.03, 0.12 and 0.25 mg/L, respectively. The new antifungal agents showed substantial activity against isolates demonstrating in vitro resistance to fluconazole and itraconazole. These results suggest that the newer antifungal agents possess promising activity against invasive Candida isolates, particularly against those with reduced susceptibility to fluconazole and itraconazole.     

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.     

Multilaboratory Testing of Antifungal Drug Combinations against Candida Species and Aspergillus fumigatus: Utility of 100 Percent Inhibition as the Endpoint

Four laboratories tested three isolates of Candida species and two isolates of Aspergillus fumigatus using 96-well plates containing combinations of amphotericin B, anidulafungin, caspofungin, micafungin, fluconazole, itraconazole, posaconazole, and voriconazole. The majority of summation fractional inhibitory concentration indices (ΣFICI) based on the Lowe additivity formula suggested indifferent drug interactions (ΣFICI > 0.5 and ≤4.0) and no instance of drug antagonism (ΣFICI > 4.0). The intra- and interlaboratory agreement rates were superior when MIC₁₀₀ readings were used as endpoints (at a 99% confidence interval [CI]).     

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 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.     

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.     

In vitro antifungal susceptibilities of uncommon basidiomycetous yeasts

The in vitro activities of eight antifungal drugs against 50 isolates of basidiomycetous yeasts were determined by a microdilution method. In general fluconazole and micafungin were inactive. Terbinafine was active only against Sporobolomyces salmonicolor. The activities of the other antifungals were variable and depended on the species tested. The new triazoles showed the lowest MICs, but amphotericin B and itraconazole were the only drugs active against Cryptococcus albidus.     

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.     

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.     

In vitro interactions of licensed and novel antifungal drugs against Fusarium spp

We have studied the in vitro interactions of amphotericin B (AMB) with terbinafine (TBF), itraconazole, voriconazole (VCZ), albaconazole, and ravuconazole (RVZ), as well as TBF combined with the same azoles, against 11 isolates of Fusarium spp. using the fractional inhibitory concentration index. The highest percentage of synergistic interactions was observed for the combinations AMB-RVZ, TBF-VCZ, and TBF-RCZ.     

In Vitro Activities of Nine Antifungal Drugs and Their Combinations against Phialophora verrucosa

The in vitro activities of nine antifungal drugs and their combinations against 31 clinical and 15 environmental Phialophora verrucosa strains were tested. The MIC₉₀/90% minimum effective concentration (MIC/MEC₉₀) values (μg/ml) across all strains were as follows: for terbinafine, 0.25; for posaconazole, 0.5; for voriconazole, 1; for itraconazole, 2; for amphotericin B, 4; for caspofungin and micafungin, 16; and for fluconazole and flucytosine, 64. The highest synergy was shown by the combination of itraconazole plus caspofungin (with synergy against 100% of the 31 clinical strains), followed by amphotericin B plus flucytosine (45.2%) and itraconazole plus terbinafine or micafungin (25.8% or 12.9%, respectively).     

In-vitro antifungal activity of liposomal nystatin in comparison with nystatin, amphotericin B cholesteryl sulphate, liposomal amphotericin B, amphotericin B lipid complex, amphotericin B desoxycholate, fluconazole and itraconazole.

The in-vitro susceptibilities of 120 clinical isolates of yeasts to liposomal nystatin were compared with those to amphotericin B lipid complex (ABLC), liposomal amphotericin B (LAB), amphotericin B cholesteryl sulphate (ABCD), amphotericin B desoxycholate, nystatin, fluconazole and itraconazole. Yeast isolates examined included strains of Candida albicans, Candida parapsilosis, Candida glabrata, Candida krusei, Candida guilliermondii, Candida tropicalis, Candida kefyr, Candida viswanathii, Candida famata, Candida rugosa, Rhodotorula rubra, Trichosporon spp., Cryptococcus laurentii and Cryptococcus neoformans. The mean MICs for all strains examined were: liposomal nystatin 0.96 mg/L; nystatin 0.54 mg/L; ABLC 0.65 mg/L; LAB 1.07 mg/L; ABCD 0.75 mg/L; amphotericin B 0.43 mg/L; fluconazole 5.53 mg/L; and itraconazole 0.33 mg/L. No significant differences were seen between the activity of liposomal nystatin and the polyene drugs or itraconazole, but liposomal nystatin was more active than fluconazole. MICs were lower than the reported blood concentrations following therapeutic doses of this drug, indicating the potential for a therapeutic use of liposomal nystatin in humans. These results indicate good activity in vitro against medically important yeasts, which compares favourably with the activities of other currently available antifungal drugs. Liposomal nystatin may have a role in the treatment of disseminated and systemic mycoses.     

In vitro activities of approved and investigational antifungal agents against 44 clinical isolates of basidiomycetous fungi

The in vitro activity of amphotericin B, fluconazole, flucytosine, itraconazole, voriconazole, and posaconazole was evaluated against 44 clinical isolates of filamentous basidiomycetous fungi. No statistically significant differences were noted between Schizophyllum commune (n = 5), Coprinus species (n = 8), Bjerkandera adusta (n = 14), and sterile, uncharacterized basidiomycetes (n = 17).     

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.     

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.     

Antifungal susceptibility of Cryptococcus neoformans and Cryptococcus gattii isolates from decayed wood of trunk hollows of Ficus religiosa and Syzygium cumini trees in north-western India

BACKGROUND: We present antifungal susceptibility data on environmental isolates of Cryptococcus neoformans (serotype A, n=117) and Cryptococcus gattii (serotype B, n=65) cultured from decayed wood of trunk hollows of Ficus religiosa and Syzygium cumini trees. METHODS: Susceptibilities to amphotericin B, fluconazole, ketoconazole, itraconazole and voriconazole were determined by using Etest. The MICs were read after 48 h as per the guidelines provided by the manufacturer. RESULTS: The MIC90s and susceptibility ranges for C. neoformans isolates were as follows: 0.094 (0.004-0.25) mg/L for amphotericin B, 4 (0.032-12) mg/L for fluconazole, 0.094 (0.004-0.75) mg/L for itraconazole, 0.064 (0.002-0.19) mg/L for ketoconazole, and 0.047 (0.006-0.125) mg/L for voriconazole, whereas for C. gattii isolates these were 0.125 (0.023-0.5) mg/L for amphotericin B, 8 (0.032-16) mg/L for fluconazole, 0.75 (0.006-2) mg/L for itraconazole, 0.125 (0.003-0.19) mg/L for ketoconazole, and 0.094 (0.004-0.125) mg/L for voriconazole. A comparison of the geometric means of MICs (mg/L) revealed that C. gattii was less susceptible than C. neoformans to amphotericin B (0.075 versus 0.051, P=0.0003), fluconazole (2.912 versus 2.316, P=0.003), itraconazole (0.198 versus 0.0344, P<0.0001), ketoconazole (0.072 versus 0.037, P<0.0001), and voriconazole (0.045 versus 0.023, P<0.0001). CONCLUSIONS: The antifungal susceptibility data obtained in this study indicate that the occurrence of primary resistance among environmental isolates of C. neoformans serotype A and C. gattii serotype B is rare, and serotype B isolates are less susceptible than serotype A isolates.     

In vitro activity of a new triazole BAL4815, the active component of BAL8557 (the water-soluble prodrug), against Aspergillus spp

OBJECTIVES: BAL4815 is the active component of the antifungal triazole agent BAL8557 (the water-soluble prodrug). We compared the in vitro activity of BAL4815 with that of itraconazole, voriconazole, caspofungin and amphotericin B against 118 isolates of Aspergillus comprising four different species (fumigatus, terreus, flavus and niger); the isolates were pre-selected to include 16 isolates demonstrating in vitro resistance to other agents. METHODS: Susceptibilities were determined for BAL4815, amphotericin B, itraconazole and voriconazole using the microdilution plate modification of the NCCLS M38-A method with RPMI 1640 buffered to pH 7.0 with MOPS; for caspofungin the method was modified using incubation in a gas mixture of 1% O2/5% CO2/94% N2 to aid reading. MFCs (> or =99% kill) were also determined for all drugs other than caspofungin. RESULTS: For all isolates, geometric mean (GM) MIC values and ranges (in mg/L) were: BAL4815, 0.620 and 0.125-2.0; itraconazole, 0.399 and 0.063->8.0; voriconazole, 0.347 and 0.125-8.0; caspofungin, 0.341 and 0.125-4.0; amphotericin B, 0.452 and 0.06-4.0. No significant differences in susceptibility to BAL4815 were seen between species and in contrast to itraconazole no isolates demonstrated MICs >2.0 mg/L. For all isolates, GM MFC values and ranges (in mg/L) were: BAL4815, 1.68 and 0.25->8.0; itraconazole, 1.78 and 0.06->8.0; voriconazole, 1.09 and 0.25->8.0; amphotericin B, 0.98 and 0.25->4.0. CONCLUSIONS: BAL4815 demonstrated promising antifungal activity against all four Aspergillus species in vitro including strains resistant to itraconazole, caspofungin or amphotericin B.     

In vitro interaction of flucytosine with conventional and new antifungals against Cryptococcus neoformans clinical isolates

Combinations of flucytosine with conventional and new antifungals were evaluated in vitro against 30 clinical isolates of Cryptococcus neoformans. Synergy determined by checkerboard analysis was observed with combinations of fluconazole, itraconazole, voriconazole, amphotericin B, and caspofungin with flucytosine against 77, 60, 80, 77, and 67% of the isolates, respectively. Antagonism was never observed. Killing curves showed indifferent interactions between triazoles and flucytosine and synergy between amphotericin B and flucytosine.     

In vitro activity and synergism of amphotericin B, azoles and cationic antimicrobials against the emerging pathogen Trichoderma spp

OBJECTIVES: The uncommon fungal pathogen Trichoderma shows increasing medical importance particularly in immunocompromised patients. Despite systemic antifungal therapy, prognosis of Trichoderma infection is poor regardless of the type of infection and the therapy used. The aim of the present study was to evaluate the in vitro activity and synergism of double antifungal combinations including amphotericin B, voriconazole, fluconazole, chlorhexidine digluconate and Akacid plus against 15 isolates of Trichoderma longibrachiatum and 1 isolate of Trichoderma harzianum. METHODS: Individual MICs were determined by using broth microdilution method following the NCCLS M38-A guidelines with standard RPMI 1640 broth. Synergy tests were performed using the chequerboard method. RESULTS: All clinical Trichoderma strains showed reduced susceptibility to fluconazole (MICs>or=64 mg/L) and amphotericin B (MICs=2 mg/L), whereas lower MICs of 0.5-1 mg/L were detected for voriconazole. Akacid plus reached the lowest MIC values in a range of 0.06-0.5 mg/L, 4- to 32-fold higher MICs were found for chlorhexidine. No antagonism was observed for any of the antifungal combinations tested. Interaction of amphotericin B and azoles was indifferent (fractional inhibitory concentration index, FICI 2-4). The combination of one azole and one cationic biocide showed different degree of synergism (FICI 0.07-2.03). Interaction of Akacid plus and chlorhexidine resulted in synergism for each Trichoderma isolate (FICI-range 0.05-0.5). CONCLUSIONS: These results demonstrate no interaction between antifungals and some degree of synergism between azoles and cationic antimicrobials against Trichoderma spp.     

Combined therapies in a murine model of blastoschizomycosis

In a murine model of blastoschizomycosis, amphotericin B combined with micafungin, flucytosine or voriconazole did not improve the efficacy of fluconazole. However, such combinations can constitute therapeutic options for those cases where fluconazole fails.