The Evaluation of Clinical Utility of ATB FUNGUS 2 for Antifungal Susceptibility Testing in Candida Species

Bae, Hye Gyung; Sohn, Yong Hak; Shin, Jong Hee; Kim, Mi Na

Abstract

BACKGROUND: Although the National Committee for Clinical Laboratory Standards (NCCLS) defined a standard reference broth microdilution method for testing the susceptibility of Candida species to antifungal drugs, many clinical laboratories require easier but reliable alternatives for routine antifungal susceptibility testing. We evaluated ATB FUNGUS 2 (bioMerieux, France.; ATB) compared to the method recommended by the NCCLS (NCCLS).
METHODS
A total of 28 strains of Candida species consecutively isolated from blood and CSF cultures at Asan Medical Center from April to June 2004 were tested. In addition, 12 strains comprising C. krusei (3), C. glabrata (7) and C. guilliermondii (2) from the collection of Chonnam National University Hospital were included in the study. These strains were tested for minimum inhibitory concentrations (MICs) against flucytosine (FC), fluconazole (FZ), itraconazole (IZ) and amphotericin B (AB) by both of ATB and NCCLS. In NCCLS, MICs were read using a spectrophotometer after 24 and 48 hour-incubation.
RESULTS
The concordance rates of MICs between ATB and NCCLS after 24 hour-incubation were 100%, 75%, 89% and 96% within two-fold dilution and 100%, 97%, 97%, 100% within four-fold dilution for FC, FZ, IZ and AB, respectively. For C. krusei, all three FC and FZ-resistant strains were either intermediate or SDD and one IZ-resistant strain was SDD in ATB, respectively. One C. tropicalis strain resulted in AB MICs of 0.5 microgram/mL in NCCLS, but 2 microgram/mL in ATB.
CONCLUSIONS
ATB showed good concordance rates with NCCLS after 24 hour-incubation. ATB appears to be a useful alternatives to NCCLS for routine antifungal susceptibility tests. However, ATB needs further evaluation with more clinical strains, especially those resistant to antifungal agents.