Antifungal Susceptibility Testing of Posaconazole (P), Itraconazole (IT), Amphotericin B (AB) and Abelcet (ABEL) against Moulds: Comparison of Methods.

C. KUZUCU1, B. RAPINO2, L. MCDERMOTT2, S. HADLEY2

Author address: 

1 Inonu University Faculty of Medicine, Malatya, Turkey, 2 Tufts-New England Medical Center, Boston, MA

Abstract: 

Background: Antifungal susceptibility testing of pathogenic moulds is in development. A simple screening semi-solid agar test (SAAS) has proved accurate for yeasts (J Clin Microbiol 2000;38). We hypothesized the SAAS test, using hyphal suspension inocula, would be rapid and easy to perform and correlate with the NCCLS broth microdilution method (M38-P) that requires conidial suspension inocula. Methods: We tested 52 clinical moulds (A. fumigatus (30), A. niger (9), A. flavus (3) A. species (5), other (5)) against 4 drugs (P, IT, AB, ABEL) comparing the M38-P and SAAS methods. For M38-P, two fold dilutions of drugs were studied in RPMI-1640 and Antibiotic Medium 3 (AM3). Drug concentrations tested for SAAS, AB and ABEL = 0.125-2.0 µg/ml; IT = 0.25-2.0 µg/ml; P = 0.25-8 µg/ml, were added to 0.5% semi-solid heart infusion agar in prepared tubes. A just turbid suspension in sterile water of mycelial growth of 7 day old fungi grown on Sabouraud's dextrose agar slants was prepared. A standard loopful was inserted vertically into the drug containing semi-solid media. Candida krusei ATCC 6258 was used as the control for all tests. All cultures were incubated at 35°C for 48 h. Visual inspection of growth compared with drug free control for both methods was used for end point determination of MIC (100% inhibition for AB, ABEL; 50% growth reduction for IT, P). Results: The concordance within 3 dilutions was: IT = 96%; P = 94%; AB (AM3) = 96%; ABEL (AM3) = 85%. By SAAS, all but one of A. fumigatus were susceptible to IT; all were susceptible to P (range: 0.25-4.0 µg/ml). ABEL MICs were
2002

abstract No: 

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Full conference title: 

42nd Interscience Conference on Antimicrobial Agents and Chemotherapy
    • ICAAC 42nd