[Establishment and evaluation of microdilution assays for the in vitro sensitivity testing of Aspergillus fumigatus].
For the in vitro sensitivity assessment of moulds different methods of micro- and macro-dilution assays as well as agar diffusion assays in different media formulations have been described so far. Until now, no standardized method has been preferred. The aim of the present study is to establish and to evaluate a microdilution assay for the in vitro chemosensitivity testing of Aspergillus fumigatus. This method should show a late onset of superficial growth and sporulation as well as a relative independency of the test inoculum. As reference substances, amphotericin B (CAS 1397-89-3) and 5-fluorocytosine (CAS 2022-85-7), which are both used for therapy of systemic mycoses, have been tested. Both substances show an excellent water solubility in liquid media. Fifty clinical isolates of A. fumigatus were used for the testings. The strains showed a better growth in Isosensitest (ISO)-medium than in Yeast-Nitrogen-Glucose (YNG)-medium. Growth was submers++ during the observation time, adherent to the bottom of the microtiter plate. Superficial growth with sporulation only occurred in a late stage of growth. Only a weak inoculum effect could be observed and the MIC (minimal inhibitory concentration) values determined macroscopically as well as using an ELISA reader showed to be almost comparable with a clearly defined breakpoint for the MIC discrimination. For amphotericin B, lower MIC values were observed in ISO-medium (0.25-2 micrograms/ml; median M = 1 microgram/ml) than in YNG-medium (0.25 microgram/ml; M = 1 microgram/ml). For 5-fluorocytosine, in both media MIC-values of > or = 32 micrograms/ml with a median of 64 micrograms/ml in ISO-medium and 128 micrograms/ml in YNG-medium were observed, respectively. With this test procedure, a standardized chemosensitivity testing can be performed for strains of A. fumigatus by a test system which is relatively easy to handle. These in vitro sensitivity data have to be correlated with clinical data as well as data obtained from animal studies. Only after this assessment final therapeutic consequences should be drawn from these in vitro findings.
Schmidt
A
A
Institut für Mikrobiologie und Virologie, Universität Witten/Herdecke.
Schmidt
D I
DI
D000666:Amphotericin B / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology*; D001232:Aspergillus fumigatus / Q000187:drug effects*; D003470:Culture Media; D005437:Flucytosine / Q000494:pharmacology; D007201:Indicator Dilution Techniques; D008826:Microbial Sensitivity Tests
D000935:Antifungal Agents; D003470:Culture Media; D000666:Amphotericin B; D005437:Flucytosine
Etablierung und Evaluierung von In-vitro-Sensibilitätstestungen an Aspergillus fumigatus mittels Mikrodilutionsverfahren.