In vitro susceptibility of clinical isolates of Zygomycota to amphotericin B, flucytosine, itraconazole and voriconazole

ABSTRACT Aspergillus fumigatus has been understood to be the most common cause of invasive aspergillosis (IA) in all epidemiological surveys. However, recent studies have uncovered a large degree of genetic heterogeneity between isolates morphologically identified as A. fumigatus, leading to the description of a new species, Aspergillus lentulus. Here, we examined the genetic diversity of clinical isolates identified as A. fumigatus using restriction enzyme polymorphism analysis and sequence-based identification. Analysis of 50 clinical isolates from geographically diverse locations recorded the presence of at least three distinct species: A. lentulus, Aspergillus udagawae, and A. fumigatus. In vitro, A. lentulus isolates demonstrated decreased susceptibility to antifungal drugs currently used for IA, including amphotericin B, voriconazole, and caspofungin; A. udagawae isolates demonstrated decreased in vitro susceptibility to amphotericin B. Results of the present study demonstrate that current phenotypic methods to identify fungi do not differentiate between genetically distinct species in the A. fumigatus group. Differential antifungal susceptibilities of these species may account for some of the reported poor outcomes of therapy in clinical studies.

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A comparative study of the broth micro- and macro-dilution techniques for the determination of the in vitro susceptibility ofAspergillus fumigatus

Canadian Journal of Microbiology ◽

10.1139/m96-123 ◽

1996 ◽

Vol 42 (9) ◽

pp. 960-964 ◽

Cited By ~ 16

Author(s):

Elias K. Manavathu ◽

George J. Alangaden ◽

Stephen A. Lerner

Keyword(s):

Aspergillus Fumigatus ◽

Amphotericin B ◽

Medical Center ◽

Acquired Resistance ◽

Inoculum Size ◽

Clinical Isolates ◽

Medium Temperature ◽

In Vitro Susceptibility ◽

Broth Macrodilution

The effects of inoculum size, medium, temperature, and duration of growth on the in vitro susceptibility testing of Aspergillus fumigatus were investigated using broth micro- and macro-dilution techniques. The minimum inhibitory concentrations (MICs) of ketoconazole, miconazole, itraconazole, fluconazole, and amphotericin B were significantly influenced by the inoculum size, regardless of the techniques used. Two- to four-fold higher MIC values were obtained when the inoculum size was increased 100-fold. The use of peptone yeast extract glucose and RPMI 1640 media provided essentially identical MIC values at 30 and 35 °C after incubation for 48 h or longer. A comparison of broth micro- and macro-dilution techniques revealed that, under equivalent conditions, the latter with an inoculum size between 1 × 103and 1 × 104conidia (strain W73355)/mL consistently provided the lowest MICs of fluconazole (256 μg/mL), ketoconazole (8 μg/mL), miconazole (2 μg/mL), itraconazole (0.25 μg/mL), and amphotericin B (0.25 μg/mL). Using the broth macrodilution technique, we screened 24 clinical isolates of A. fumigatus obtained from the Detroit Medical Center in 1994. The MIC values of fluconazole, ketoconazole, miconazole, itraconazole and amphotericin B for all the isolates were 128–256, 8–16, 1–2, 0.25–0.5, and 0.25–1.0 μg/mL, respectively, indicating that none of the clinical isolates that we tested shows acquired resistance to the antifungals used.Key words: Aspergillus fumigatus, susceptibility test, antifungals, drug resistance, broth macrodilution.

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In vitro susceptibility to antifungal agents of clinical and environmental Cryptococcus neoformans isolated in Southern of Brazil

Revista do Instituto de Medicina Tropical de São Paulo ◽

10.1590/s0036-46652001000500006 ◽

2001 ◽

Vol 43 (5) ◽

pp. 267-270 ◽

Cited By ~ 14

Author(s):

Sydney Hartz ALVES ◽

Loiva T. OLIVEIRA ◽

Jane M. COSTA ◽

Irina LUBECK ◽

Agnes Kiesling CASALI ◽

...

Keyword(s):

Cryptococcus Neoformans ◽

Amphotericin B ◽

Antifungal Agents ◽

Susceptibility Testing ◽

Clinical Isolates ◽

Environmental Isolates ◽

Aids Patients ◽

In Vitro Susceptibility ◽

Minimal Inhibitory Concentrations

The purpose of the present study was to compare the susceptibility to four antifungal agents of 69 Cryptococcus neoformans strains isolated from AIDS patients with that of 13 C. neoformans strains isolated from the environment. Based on the NCCLS M27-A methodology the Minimal Inhibitory Concentrations (MICs) obtained for amphotericin B, itraconazole and ketoconazole were very similar for clinical and environmental isolates. Clinical isolates were less susceptible to fluconazole than environmental isolates. The significance of these findings and aspects concerning the importance, role and difficulties of C. neoformans susceptibility testing are also discussed.

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Activity of a new triazole, Sch 56592, compared with those of four other antifungal agents tested against clinical isolates of Candida spp. and Saccharomyces cerevisiae.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.41.2.233 ◽

1997 ◽

Vol 41 (2) ◽

pp. 233-235 ◽

Cited By ~ 65

Author(s):

M A Pfaller ◽

S Messer ◽

R N Jones

Keyword(s):

Saccharomyces Cerevisiae ◽

Antifungal Activity ◽

Amphotericin B ◽

Clinical Laboratory ◽

Clinical Isolates ◽

National Committee ◽

Candida Spp ◽

In Vitro Susceptibility ◽

Broth Microdilution Method

Sch 56592 is a new triazole agent with potent, broad-spectrum antifungal activity. The in vitro activities of Sch 56592, itraconazole, fluconazole, amphotericin B, and flucytosine (5-FC) against 404 clinical isolates of Candida spp. (382 isolates) and Saccharomyces cerevisiae (22 isolates) were investigated. In vitro susceptibility testing was performed by a broth microdilution method performed according to National Committee for Clinical Laboratory Standards guidelines. Overall, Sch 56592 was very active (MIC at which 90% of isolates are inhibited [MIC90], 0.5 microgram/ml) against these yeast isolates. Sch 56592 was most active against Candida tropicalis, Candida parapsilosis, candida lusitaniae, and Candida stellatoidea (MIC90, < or = 0.12 microgram/ml) and was least active against Candida glabrata (MIC90, 2.0 micrograms/ml). Sch 56592 was 2- to 32-fold more active than amphotericin B and 5-FC against all species except C. glabrata. By comparison with the other triazoles, Sch 56592 was equivalent to itraconazole and greater than or equal to eightfold more active than fluconazole. On the basis of these results, Sch 56592 has promising antifungal activity, and further in vitro and in vivo investigations are warranted.

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Sterol and Fatty Acid Composition of Candida lusitaniae Clinical Isolates

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.46.2.531-533.2002 ◽

2002 ◽

Vol 46 (2) ◽

pp. 531-533 ◽

Cited By ~ 9

Author(s):

F. Peyron ◽

A. Favel ◽

R. Calaf ◽

A. Michel-Nguyen ◽

R. Bonaly ◽

...

Keyword(s):

Fatty Acid ◽

Amphotericin B ◽

Fatty Acid Pattern ◽

Sterol Composition ◽

Clinical Isolates ◽

Cationic Dye ◽

In Vitro Susceptibility ◽

Candida Lusitaniae ◽

Fatty Acid Compositions

ABSTRACT The sterol and fatty acid compositions of four amphotericin B-resistant and of two amphotericin B-susceptible Candida lusitaniae clinical isolates were determined. A flow cytofluorometric susceptibility test (FCST) with a membrane potential-sensitive cationic dye was used as a complement to the conventional method for selecting the isolates. Compared to susceptible isolates, resistant ones showed a greatly reduced ergosterol content and changes in sterol composition, consistent with a defect in Δ8→7 isomerase. Within each group, no correlation between the sterol or fatty acid pattern or composition and both the degree of in vitro susceptibility and FCST MIC was found.

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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

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.46.4.1032-1037.2002 ◽

2002 ◽

Vol 46 (4) ◽

pp. 1032-1037 ◽

Cited By ~ 248

Author(s):

M. A. Pfaller ◽

S. A. Messer ◽

R. J. Hollis ◽

R. N. Jones

Keyword(s):

Amphotericin B ◽

Filamentous Fungi ◽

Antifungal Agents ◽

Clinical Laboratory ◽

The United States ◽

Clinical Isolates ◽

National Committee ◽

Surveillance Program ◽

In Vitro Susceptibility

ABSTRACT 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 ≤1 μg/ml, followed by voriconazole (91%), amphotericin B (89%), ravuconazole (88%), and itraconazole (70%). All three new triazoles demonstrated excellent activity (MIC, ≤1 μg/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 [MIC50], >8 μg/ml) or Mucor spp. (MIC50, >8 μg/ml). Posaconazole and ravuconazole were more active than voriconazole against Rhizopus spp. (MIC50, 1 to 2 μg/ml versus >8 μg/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.

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