Multicenter Study of Method-Dependent Epidemiological Cutoff Values for Detection of Resistance in Candida spp. and Aspergillus spp. to Amphotericin B and Echinocandins for the Etest Agar Diffusion Method

Abstract

Method-dependent Etest epidemiological cutoff values (ECVs) are not available for susceptibility testing of either Candida or Aspergillus species with amphotericin B or echinocandins. In addition, reference caspofungin MICs for Candida spp. are unreliable. Candida and Aspergillus species wild-type (WT) Etest MIC distributions (microorganisms in a species-drug combination with no detectable phenotypic resistance) were established for 4,341 Candida albicans, 113 C. dubliniensis, 1,683 C. glabrata species complex (SC), 709 C. krusei, 767 C. parapsilosis SC, 796 C. tropicalis, 1,637 Aspergillus fumigatus SC, 238 A. flavus SC, 321 A. niger SC, and 247 A. terreus SC isolates. Etest MICs from 15 laboratories (in Argentina, Europe, Mexico, South Africa, and the United States) were pooled to establish Etest ECVs. Anidulafungin, caspofungin, micafungin, and amphotericin B ECVs (in micrograms per milliliter) encompassing Ն97.5% of the statistically modeled population were 0.016, 0.5, 0.03, and 1 for C. albicans; 0.03, 1, 0.03, and 2 for C. glabrata SC; 0.06, 1, 0.25, and 4 for C. krusei; 8, 4, 2, and 2 for C. parapsilosis SC; and 0.03, 1, 0.12, and 2 for C. tropicalis. The amphotericin B ECV was 0.25 g/ml for C. dubliniensis and 2, 8, 2, and 16 g/ml for the complexes of A. fumigatus, A. flavus, A. niger, and A. terreus, respectively. While anidulafungin Etest ECVs classified 92% of the Candida fks mutants evaluated as non-WT, the performance was lower for caspofungin (75%) and micafungin (84%) cutoffs. Finally, although anidulafungin (as an echinocandin surrogate susceptibility

Site-Directed Mutagenesis of the 1,3-β-Glucan Synthase Catalytic Subunit of Pneumocystis jirovecii and Susceptibility Assays Suggest Its Sensitivity to Caspofungin

“…One out of two experiments that gave similar results is reported here. Although obtained using various methods that have various sensitivities, the MICs previously published correspond roughly to ours for the S. cerevisiae WT (0.25 versus 0.03 to 0.4 g/ml [15,16,21]) and gsc1 deletant (0.12 to 0.125 versus 0.0015 to 0.1 g/ml [15,16,21]), as well as for C. albicans (0.12 to 0.380 versus 0.12 to 0.25 g/ml [22,41]) and C. parapsilosis (0.50 versus 0.25 to 8 g/ml [41 -43]).…”

“…2]). According to Espinel-Ingroff et al (41) and Canton et al (42), the MICs of CAS for C. parapsilosis that we obtained were below the epidemiological cutoff values for both Etest and YeastOne methods (0.5 versus 4 and 0.5 versus 2 g/ml, respectively). The MICs for C. albicans we obtained were also below the epidemiological cutoff values of wild-type isolates (0.38 versus 0.5 and 0.12 versus 0.25 g/ml, respectively).…”

“…S1. as the S. cerevisiae gsc1 deletant complemented with the GSC1 gene of these two Candida species. CAS presents low MICs for the former Candida species, whereas it presents high MICs for the latter (41,42). The natural high MICs for C. parapsilosis are due to a polymorphism at the end of the hot spot no.…”

Fluconazole and Echinocandin Resistance of Candida glabrata Correlates Better with Antifungal Drug Exposure Rather than with MSH2 Mutator Genotype in a French Cohort of Patients Harboring Low Rates of Resistance

“…We used breakpoint tables of the EUCAST document v8.0 (http://www.eucast.org/clinical_breakpoints/), which were valid as of November 16, 2015 (European Committee on Antimicrobial Susceptibility Testing (EUCAST), 2015), and the EUCAST and Etest® database of MIC distribution and ECOFFs (http://www.mic.eucast.org). Isolates were categorized as high fluconazole MICs for MICs > 32 mg/L and high micafungin MICs for MICs > 0.03 mg/L (Espinel-Ingroff et al, 2016). Notably, some isolates, including reference strain ATCC MYA 2950 displayed macrocolonies in the inhibition ellipse of Etest® after 48 h of incubation with fluconazole.…”

Molecular Analysis of Resistance and Detection of Non-Wild-Type Strains Using Etest Epidemiological Cutoff Values for Amphotericin B and Echinocandins for Bloodstream Candida Infections from a Tertiary Hospital in Qatar

“…The susceptibility profiles of the Candida species were determined using the Etest method according to the manufacturer's instructions (Liofilchem, Italy). Clinical breakpoints (CBP) were not available for Etest; therefore, the epidemiological cutoff values (ECV) proposed by Espinel-Ingroff et al (38) were used for caspofungin, anidulafungin, micafungin, and amphotericin B. As such, MICs obtained with the above-mentioned antifungals were classified as wild type (WT) or non-WT depending on whether the MIC was less than or equal to the ECV or greater than the ECV, respectively.…”