Evaluation of the FUNGIFAST® AFG yeast antifungal susceptibility test : comparison with EUCAST and the E-Test method

INTERNAL STUDY - (ELITECH GROUP - INTERNATIONAL MICROBIO - SIGNES)

OBJECTIVESOBJECTIVES

MATERIEL AND METHODSMATERIEL AND METHODS

RESULTSRESULTS

CONCLUSIONCONCLUSION

REFERENCESREFERENCES

FUNGIFAST® AFG (INTERNATIONAL MICROBIO), a commercial tray based on a microdilution method, allows the susceptibility testing of 5 antifungals: amphotericin B (AB), flucytosine (5 FC), fluconazole (FCZ), itraconazole (ITZ) and voriconazole (VRZ).

The aim of this internal study is to evaluate the tray in comparison with the reference method of EUCAST on 56 yeast clinical isolates and in comparaison with the commercial E-Test method (AB Biodisk) on 100 yeast clinical isolates (10 species).

Testing was performed on a sample of yeasts isolates (n=56 or 100) and 3 ATCC collection strains (Candida albicans 90029, C. glabrata 90030 and Cryptococcus neoformans 32045).Species :Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis , Candida lusitaniae, Candida krusei, Candida kefyr, Candida guilliermondii, Saccharomyces cerevisiae, Cryptococcus neoformans.The strains were provided by hospitals or private laboratories. Each strain was subcultured for 24h in SABOURAUD medium and tested in parallel with E-Test (RPMI agar) for amphotericin B, flucytosine, itraconazole, fluconazole and voriconazole and EUCAST broth micro dilution method for flucytosine, itraconazole, fluconazole and voriconazole .For EUCAST, MICs 50% were read spectrophotometrically after 24h (or 48h). For Etest, MICS were read after 24 h (or 48h) For FUNGIFAST ® AFG, 10L of inoculated suspension medium (2McF) was added to the MES FUNGI medium, and 100L was inoculated in each well. Colorimetric reading was performed at 24h (or 48h) with a change in the growth indicator from dark violet to pink or colourless.

FUNGIFAST® AFG did not demonstrate a lack of growth, and 93% of the MIC values were obtained after 24h. The MIC values of the QC strains showed good agreement and were within the reported limits.

The percentage of category agreement between FUNGIFAST® AFG vs. reference methods are given in the table 3

AB 5-FC ITZ FCZ VRZ

overall rate of agreement

(%)

nb. of strains

ND n = 56 n = 56 n = 56 n = 56

EUCAST

ND 92.9% 69.6% 73.2% 92.9% 82.2%

nb. of strains

n = 100 n = 99 n = 99 n = 99 n = 100

Etest

99% 90.9% 79.8% 84.8% 97% 90.3%

Fungifast® AFG tray

GROWTHNO

GROWTH

Reading criteria

Table 3 : % of category agreement of Fungifast® AFG tray vs reference methods

FUNGIFAST® AFG test is simple to perform and the colorimetric reading is less subjective than that of the reference method.

With an overall rate of agreement of 82.2% versus EUCAST and 90.3% versus Etest, the FUNGIFAST® AFG test can be recommended as an other method for the routine antifungal susceptibility testing of yeast clinical isolates.

This test is a rapid, easy-to-use, easy-to-read and suitable for all clinical laboratories.

Subcommitee of Antifungal Testing of the European Commitee on Antibiotic Sucseptibility Testing of the European Society of Clinical Microbiology and Infectious Diseases. 2002. Method for the determination of Minimum Inhibitory Concentration (MIC) by Broth Dilution of Fermentative Yeasts. EUCAST Discussion document E. Dis. 7.1 ESCMID.

REX J.H. et al. Antifungal susceptibility testing: pratical aspects and current challenges. Clin. Microbiol. Rev. 2001,14:643-658.