Comparison of Etest and NCCLS M38-A methods for testing susceptibilities of filamentous fungi to posaconazole

E. Lopez Oviedo,1 C. Martin Martí­n de la Escalera,1 A.I. Aller,1 M. Ramirez,1 C. Castro,1 A. Romero,1 J. Peman,2 E.

Author address: 

1H.U.Valme, Microbiologí­a, Sevilla, Spain and 2H.U.La Fe, Microbiologí­a, Valencia, Germany

Abstract: 

Background: Posaconazole is a new triazole derivate and structural analogue of Itraconazole. This drug has fungicidal activity against yeast and filamentous fungi. The purpose of our study was to compare Etest method (ET) with broth microdilution NCCLS M38-A (MD) for ’in vitro’ susceptibility testing of filamentous fungi isolates against posaconazole. Methods: Etest method andMDMICs were realized simultaneously for 79 isolates: 56 Aspergillus spp (19 A. terreus, 17A. fumigatus, 14A. flavus, 3 A. glaucus, 2 A. niger and 1 A. nidulans), 10 Zygomicetes (6 Rhizopus spp., 4 Mucor spp.), 9 Scedosporium spp. (6 S. apioespermum, 3 S. prolificans) and 3 Fusarium spp. Quality control strains C. parapsilosis 22019, C. krusei 6258, A. flavus 204304 and A. fumigatus 204305. ET MICs were determined on solidified RPMI 1640 medium (2% glucose) after 24 and 48 h of incubation at 35 C, M38-A MICs were read after 48 h. With both methods, MICs were determined by the lowest drug dilution that showed 100% inhibition (MIC48). The agreement (percentage of MICs pairs within a two dilutions range) between ET andMDMICs were calculated. Results: At 24 h ET/48 h MD the MIC50 and MIC90 (mg l-1) were as follows respectively: Aspergillus spp, ET 0.125/0.25 and MD 0.06/0.25; Zygomicetes, ET 1/2 and MD 0.25/0.5; S. prolificans, ET 32/32 and MD 8/8; S. apioespermum, ET NG/NG (NG, nongrowth) and MD 1/1; Fusarium spp., ET 32/32 & MD 8/8. At 48 h ET and 48 h MD not difference were observed except for Zygomicetes which showed overgrowth at this time of reading and S. apioespermum which showed MICs value 48/48 of 2/8 and 0.5/1 The agreement (ET/MD):in the different groups were Aspergillus spp. 24/48: 93%, 48/48: 83.3%; Zygomicetes 24/48: 60%, 48/48: 10%; S. apioespermum 48/48: 50%, S. prolificans :24/48 100% 48/48:100% Fusarium spp. 24/48: 100%, 48/48: 100%. Conclusions: (i) The best ’in vitro’ activity was observed for Fusarium spp. and Aspergillus spp. followed by Zygomicetes and S. apioespermum. (ii) The highest agreement was observed for Fusarium spp. and Aspergillus spp. (iii) Etest method by reading after 24 h incubation time could easily replace the time-consuming NCCLS M38A reference method, except S. apioespermum.
2005

abstract No: 

P018

Full conference title: 

2nd Trends in Medical Mycology
    • TIMM 2nd (2010)