Comparison of NCCLS and 3-(4,5-dimethyl-2-thiazyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) methods of in vitro susceptibility testing of filamentous fungi and development of a new simplified method

Citation
J. Meletiadis et al., Comparison of NCCLS and 3-(4,5-dimethyl-2-thiazyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) methods of in vitro susceptibility testing of filamentous fungi and development of a new simplified method, J CLIN MICR, 38(8), 2000, pp. 2949-2954
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Clinical Immunolgy & Infectious Disease",Microbiology
Journal title
JOURNAL OF CLINICAL MICROBIOLOGY
ISSN journal
0095-1137 → ACNP
Volume
38
Issue
8
Year of publication
2000
Pages
2949 - 2954
Database
ISI
SICI code
0095-1137(200008)38:8<2949:CONA3>2.0.ZU;2-J
Abstract
The susceptibility of 30 clinical isolates belonging to six different speci es of filamentous fungi (Aspergillus fumigatus, Aspergillus flavus, Scedosp orium prolificans, Scedosporium apiospermum, Fusarium solani, and Fusarium oxysporum) was tested against six antifungal drugs (miconazole, voriconazol e, itraconazole, UR9825, terbinafine, and amphotericin B) with the microdil ution method recommended by the National Committee for Clinical Laboratory Standards (NCCLS) (M38-P), The MICs were compared with the MICs obtained by a colorimetric method measuring the reduction of the dye 3-(4,5-dimethyl-2 -thiazyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan by viable f ungi. The levels of agreement between the two methods were 96 and 92% for M IC-0 (clear wells) and MIC-1 (75% growth reduction), respectively, The leve ls of agreement were always higher for Aspergillus spp, (97% +/- 2.5%), fol lowed by Scedosporium spp, (87% +/- 10.3%) and Fusarium spp. (78% +/- 7.8%) , The NCCLS method was more reproducible than the MTT method: 98 versus 95% for MIC-0 and 97 versus 90% for MIC-1. However, the percentage of hyphal g rowth as determined visually by the NCCLS method showed several discrepanci es when they were compared with the percentages of MTT reduction. A new sim plified assay that incorporates the dye MTT with the initial inoculum and i n which the fungi are incubated with the dye for 48 h or more was developed , showing comparable levels of agreement and reproducibility with the other two methods. Furthermore, the new assay was easier to perform and more sen sitive than the MTT method.