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Journal of Clinical Microbiology, April 2001, p. 1328-1333, Vol. 39, No. 4
0095-1137/01/$04.00+0   DOI: 10.1128/JCM.39.4.1328-1333.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Evaluation of Etest for Direct Antifungal Susceptibility Testing of Yeasts in Positive Blood Cultures

Hsein Chang Chang,1 Jui Jung Chang,1 Shih Huang Chan,2 Ay Huey Huang,3 Tsu Lan Wu,4 Miao Chu Lin,5 and Tsung Chain Chang5,*

Institute of Medical Engineering,1 Department of Statistics,2 and Department of Medical Technology, College of Medicine,5 National Cheng Kung University, Division of Clinical Microbiology, Department of Pathology, National Cheng Kung University Hospital,3 and Department of Clinical Pathology, Linko Medical Center, Chang Gung Memorial Hospital,4 Tainan 701, Taiwan, Republic of China

Received 8 August 2000/Returned for modification 25 September 2000/Accepted 28 January 2001

The performance of the Etest (AB BIODISK, Solna, Sweden) for direct antifungal susceptibility testing of yeasts in positive blood cultures was compared with that of the macrodilution method for determining the MICs of five antifungal agents. Culture broths with blood from bottles positive for yeasts were inoculated directly onto plates for susceptibility testing with the Etest, and the MICs were read after 24 and 48 h of incubation. A total of 141 positive blood cultures (72 cultures of Candida albicans, 31 of Candida tropicalis, 14 of Candida glabrata, 11 of Candida parapsilosis, 3 of Candida krusei, and 3 of Cryptococcus neoformans, 4 miscellaneous yeast species, and 3 mixed cultures) were tested, and the rates of MIC agreement (±1 log2 dilution) between the direct Etest (at 24 and 48 h, respectively) and macrodilution methods were as follows: amphotericin B, 81.8 and 93.5%; flucytosine, 84.8 and 87.7%; fluconazole, 89.4 and 85.5%; itraconazole, 69.7 and 63.8%; ketoconazole, 87.9 and 79.0%. By a large-sample t test, the difference in log2 dilution between the direct Etest and the macrodilution method was found to be small (P < 0.05). The lone exceptions were ketoconazole at 48 h of incubation and itraconazole at both 24 and 48 h of incubation (P > 0.05). By Tukey's multiple comparisons, the difference between the direct Etest (48 h) and reference methods among different species was found to be less than 1 log2 dilution. When the MICs were translated into interpretive susceptibility, the minor errors caused by the direct Etest (at 24 and 48 h, respectively) were as follows: flucytosine, 2.3 and 1.4%; fluconazole, 3.0 and 3.6%; itraconazole, 21.2 and 21.3%. Itraconazole also produced an additional 3.0 and 3.6% major errors as determined by the direct Etest at 24 and 48 h, respectively. It was concluded that, except for itraconazole, the Etest method was feasible for direct susceptibility testing of blood cultures positive for yeasts. The method is simple, and the results could be read between 24 and 48 h after direct inoculation, whenever the inhibition zones were discernible.


* Corresponding author. Mailing address: Department of Medical Technology, College of Medicine, National Cheng Kung University, 1 University Rd., Tainan 701, Taiwan, Republic of China. Phone: 886-6-2353535, ext. 5790. Fax: 886-6-2363956. E-mail: tsungcha{at}mail.ncku.edu.tw.


Journal of Clinical Microbiology, April 2001, p. 1328-1333, Vol. 39, No. 4
0095-1137/01/$04.00+0   DOI: 10.1128/JCM.39.4.1328-1333.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.



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