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Journal of Clinical Microbiology, July 2001, p. 2513-2517, Vol. 39, No. 7
Servicio de Micología, Centro
Nacional de Microbiología, Instituto de Salud Carlos III,
28220 Majadahonda, Spain
Received 22 January 2001/Returned for modification 2 April
2001/Accepted 13 May 2001
Recently, the methodology that will serve as a basis of the
standard for antifungal susceptibility testing of fermentative yeasts
of the European Committee on Antibiotic Susceptibility Testing has been
described. This procedure employs a spectrophotometric method for both
inoculum adjustment and endpoint determination. However, the
utilization of a spectrophotometer requires studies for
standardization. The present work analyzes the following parameters: (i) accuracy of inoculum preparation, (ii) correlation between optical
density and CFU per milliliter, (iii) influence of the wavelength on
the endpoint determination, and (iv) influence of the dimethyl
sulfoxide concentration on the growth kinetics. The main results can be
summarized as follows: (i) inoculum preparation following the
methodology recommended by the National Committee for Clinical
Laboratory Standards is an exact procedure; (ii) the relationship
between optical density and CFU per milliliter is linear (coefficient
of determination, r2 = 0.84); (iii) MICs
obtained by means of spectrophotometric readings at different
wavelengths are identical (for amphotericin B, an intraclass
correlation coefficient of 0.98 was obtained; for fluconazole, the
intraclass correlation coefficient was 1); and (iv) a 2% concentration of dimethyl sulfoxide produces a significantly slower and lower growth
curve of Candida spp. than other concentrations.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.7.2513-2517.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Standardization of Antifungal Susceptibility
Variables for a Semiautomated Methodology
*
Corresponding author. Mailing address: Servicio de
Micología, Centro Nacional de Microbiología, Instituto
de Salud Carlos III, Ctra Majadahonda-Pozuelo km. 2, 28220 Majadahonda,
Spain. Phone: 34 91 5097961. Fax: 34 91 5097966. E-mail:
juanl.rodriguez-tudela{at}isciii.es.
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