Espinel-Ingroff A, Canton E, Peman J, Rinaldi MG, Fothergill AW
Comparison of 24-hour and 48-hour voriconazole MICs as determined by the Clinical and Laboratory Standards Institute broth microdilution method (M27-A3 document) in three laboratories: Results with 2,162 clinical Candida spp. and other yeast isolates. [JOURNAL ARTICLE]
J Clin Microbiol 2009 Jul 1.
We evaluated the performance of the 24 h broth microdilution voriconazole MIC by obtaining MICs for 2,162 clinical isolates of Candida spp. and other yeasts; the 24 h results were compared to 48h reference MICs to assess essential as well as categorical agreement. Although overall essential agreement was 88.6%, it ranged from 96.4 to 100% for six of the 11 species or groups of yeasts tested. The overall categorical agreement was 93.2% and was above 90% for eight species. However, unacceptable percentages of very major errors (false susceptibility) were observed for C. albicans (2.7%), C. glabrata (4.1%), C. tropicalis (9.7%) and other less common yeast species (9.8%). Since it is essential to identify potentially resistant isolates and breakpoints are based on 48 h MICs, it appears that the 24 h MIC is not as clinically useful as the 48 h reference MIC. However, further characterization of these falsely susceptible MICs for three of the four common Candida spp. is needed to understand if these errors are due to trailing misinterpretation or if the 48 h incubation is required to detect voriconazole resistance. Either in vivo versus in vitro correlations or the determination of resistance mechanisms should be investigated.
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