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Journal of Clinical Microbiology, Mar 1995, 661-667, Vol 33, No. 3
B Jahn, E Martin, A Stueben and S Bhakdi
We describe a simple microtiter method for determining the susceptibility
of Candida albicans and hyphal forms of Aspergillus fumigatus against
antifungal agents. The assay measures mitochondrial respiration by
determining reduction of 3-(4,5-dimethyl-2-thiazolyl)-
2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan, a process that is
enhanced in the presence of menadione. C. albicans or conidial suspensions
of A. fumigatus are seeded into microtiter plates. Hyphal outgrowth of
Aspergillus spp. was achieved by a 12 to 14-h culture at 30 degrees C.
Antifungal agents (amphotericin B, fluconazole, itraconazole) were added to
the cultures for 24 h. Thereafter, incubations were continued for 3 h in
the presence of MTT plus 0.1 mM menadione. Formazan formation was
quantified photometrically after extraction of the formazan with acid
isopropanol. Well-defined dose- response curves reflecting impairment of
mitochondrial function by the antifungal agents were obtained. With C.
albicans, the results correlated excellently with the MIC determinations
performed according to the standard macrodilution procedure. In
confirmation of a recent report, it was found that fluconazole was unable
to exert its fungistatic action on a sensitive C. albicans strain in the
presence of serum. The presented method can easily be integrated in the
standard repertoire of a diagnostic microbiology laboratory and should
prove useful as a means to assess the antifungal action of various agents
on yeasts and filamentous fungi in the presence and absence of serum
proteins or body fluids.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Susceptibility testing of Candida albicans and Aspergillus species by a simple microtiter menadione-augmented 3-(4,5-dimethyl-2-thiazolyl)-2,5- diphenyl-2H-tetrazolium bromide assay
Institute of Medical Microbiology and Hygiene, Hochhaus am Augustusplatz, Mainz, Germany.
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