In Vitro Susceptibility Testing of Aspergillus fumigatus against Posaconazole: Comparison of NCCLS M38-P and E-Test Methods

Marie-Pierre HAYETTE, Agata AMADORE, Laurence SEIDEL, Geneviève CHRISTIAENS, M. G. GARRINO, Pierrette MELIN, Youri GLUPCZYNSKI, Patrick DE MOL

Author address: 



Background: Posaconazole is a second-generation triazole and structural analogue of itraconazole. This drug has fungicidal activity against yeasts and filamentous fungi. The aim of our study was to evaluate E-test method for in vitro susceptibility testing of Aspergillus fumigatus isolates against posaconazole. Methods: A total of 121 isolates of A. fumigatus were selected as follows: 106 clinical strains from colonized patients, 18 from patients with invasive aspergillosis and 7 environmental isolates. Their in vitro susceptibility was evaluated by E-test (Abbiodisk, Sweden) and compared with NCCLS microdilution reference method (M38-P). Both tests were performed with RPMI 1640 medium at 35°C. MIC values were read after 24h (MIC-24h) and 48h (MIC-48h) incubation time by E-test method. Two MIC endpoints were determined by NCCLS method: visible reduction of growth (MIC-0); 2. 50% reduction (or more) of growth (MIC-2). Three A. fumigatus reference strains (IHEM 5734, 6149 and 13935) were included as control. Results: Geometric mean MICs (µg/ml) were respectively 0.02 for E-test at 24h and 0.029 at 48h. MIC-0 and MIC-2 values were respectively 0.19 and 0.018 µg/ml. One correlation between both methods was observed for MICs-24h and MICs-2s (p<.05 however="" there="" was="" no="" significant="" difference="" according="" to="" origin="" of="" isolates="" conclusions:="" this="" study="" assessed="" the="" potent="" role="" posaconazole="" against="" a.="" fumigatus="" with="" very="" low="" mics.="" mic="" values="" were="" not="" predictive="" pathogenicity.="" e-test="" method="" by="" reading="" after="" time="" could="" easily="" replace="" time-consuming="" nccls="" m38-p="" reference="" method.="">

abstract No: 


Full conference title: 

    • ICAAC 42nd