Correlation between Etest^®, disk diffusion, and microdilution methods for antifungal susceptibility testing of Candida species from infection and colonization

Abstract

The correlation between the microdilution (MD), Etest (ET), and disk diffusion (DD) methods was determined for amphotericin B, itraconazole and fluconazole. The minimal inhibitory concentration (MIC) of those antifungal agents was established for a total of 70 Candida spp. isolates from colonization and infection. The species distribution was: Candida albicans (n=27), C. tropicalis (n=17), C. glabrata (n=16), C. parapsilosis (n=8), and C. lusitaniae (n=2). Non-Candida albicans Candida species showed higher MICs for the three antifungal agents when compared with C. albicans isolates. The overall concordance (based on the MIC value obtained within two dilutions) between the ET and the MD method was 83% for amphotericin B, 63% for itraconazole, and 64% for fluconazole. Considering the breakpoint, the agreement between the DD and MD methods was 71% for itraconazole and 67% for fluconazole. The DD zone diameters are highly reproducible and correlate well with the MD method, making agar-based methods a viable alternative to MD for susceptibility testing. However, data on agar-based tests for itraconazole and amphotericin B are yet scarce. Thus, further research must still be carried out to ensure the standardization to other antifungal agents.

Correlation between microdilution, Etest, and disk diffusion methods for antifungal susceptibility testing of fluconazole against Candida sp. blood isolates

“…isolated in Brazil, a correlation approaching 70% between the methods was found. In our study, the agreement was higher, exceeding 90% 6,7 . Based on these results and on studies that evaluated a high number of strains of Candida sp., we can conclude that the disk diffusion test correlated well with the other methods of assessing susceptibility.…”

Molecular identification and antifungal susceptibility of 186 Candida isolates from vulvovaginal candidiasis in southern China

“…Currently, agar-based susceptibility methods including disk diffusion and the E-test are feasible due to their simplicity, reproducibility and non-requirement for specialized equipment (Negri et al, 2009). The Neo-Sensitabs tablet diffusion method offers simple, quick and costeffective susceptibility testing for determining the inhibition zone diameter of antifungal agents and is comparable to the Clinical and Laboratory Standards Institution (CLSI) M27-A2 assay for testing for yeasts and filamentous fungi in clinical laboratories (Espinel-Ingroff & Canton, 2008).…”

Antifungal activity and detailed chemical characterization of Cistus ladanifer phenolic extracts

“…However, several non-Candida albicans Candida (NCAC) spp, such as C. tropicalis, C. parapsilosis, and C. glabrata, have been increasingly implicated in human disease (Costa et al, 2010;Martins et al, 2010). This increased incidence can be attributed to improved identification methods but can also be a reflection of the high level of resistance often exhibited by NCAC species to antifungal agents (González et al, 2008;Negri et al, 2009). …”