Comparison of the Sensititre YeastOne colorimetric antifungal panel with the modified Clinical and Laboratory Standards Institute broth microdilution (M38-A) method for antifungal susceptibility testing of dermatophytes.
BACKGROUND
To compare the susceptibility of different dermatophyte species to itraconazole (I), fluconazole (F) and voriconazole (V) by the modified reference (microdilution, CLSI M38-A) and the colorimetric method Sensititre YeastOne. The microdilution method is not very practical for use in routine susceptibility testing in the clinical laboratory, thus necessitating the use of other methods.


METHODS
We studied a total of 46 dermatophyte strains isolated from clinical specimens. The microdilution reference susceptibility testing was performed following the CLSI M38-A document, using I, F and V drugs. The MIC were defined as the lowest drug concentration that produced 100% (I and V) and 50% inhibition (F) after 72 h incubation at 35 degrees C. The Sensititre MIC were detected by a change in color from pink to blue or purple.


RESULTS
Agreement levels between the 2 methods (+/-2 dilutions) for I, F and V were 30, 53.3 and 83.3%, 0, 12.5 and 66.6% and 37.5, 44.4 and 75% for Trichophyton mentagrophytes, Trichophyton rubrum and Microsporumgypseum, respectively. The MIC(50/90) (mg/l) of I, F and V for T. mentagrophytes were 0.25/0.5, 16/64 and 0.12/0.25 by the microdilution method and 0.016/0.06, 8/16 and 0.03/0.06 by the Sensititre method. The MIC for I, F and V for T. rubrum were 0.25/1, 8/64 and 0.25/0.5 by the microdilution and 0.008/0.03, 2/8, 0.016/0.03 by the Sensititre method. For M. gypseum, MIC were 0.5/1 (I), /256 (F) and 0.25/1 (V) as well as 0.016/0.25 (I), 16/256 (F) and 0.06/0.25 (V) by the microdilution and Sensititre methods, respectively.


CONCLUSIONS
The MICs obtained were lower by the Sensititre than the microdilution method. The best correlation between both methods was obtained for V in T. mentagrophytes (>80%), but was low for T. rubrum. Although the Sensititre method is easy to use in a clinical laboratory, it shows poor agreement with the reference method for dermatophytes.
Castro
C
C
Sevicio de Microbiología, Hospital Universitario Valme, Seville, Spain.
Serrano
M C
MC
Valverde
A
A
Pemán
J
J
Almeida
C
C
Martín-Mazuelos
E
E
D000935:Antifungal Agents / Q000494:pharmacology*; D003883:Arthrodermataceae / Q000187:drug effects*; D003124:Colorimetry / Q000379:methods* / Q000592:standards; D007201:Indicator Dilution Techniques; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000592:standards
D000935:Antifungal Agents