TY - JOUR
T1 - EUCAST reference testing of rezafungin susceptibility and impact of choice of plastic plates
AU - Arendrup, Maiken Cavling
AU - Jørgensen, Karin Meinike
AU - Hare, Rasmus Krøger
AU - Cuenca-Estrella, Manuel
AU - Zaragoza, Oscar
PY - 2019
Y1 - 2019
N2 - Rezafungin is a new long-acting echinocandin currently in phase 3 development. Epidemiological cutoff values are necessary for breakpoint setting but have not been established due to unexplained interlaboratory MIC variations observed in a prior multicenter study. Here we investigated if the choice of microtiter plates affected the variability when anidulafungin was included as a comparator. Testing by the EUCAST E.Def 7.3.1 reference method using tissue and cell culture-treated polystyrene plates (TC plates) and untreated polystyrene plates (UT plates) from four manufacturers was performed. Six control strains (Candida albicans, n 3; C. krusei, n 2; C. parapsilosis, n 1) were tested (520 MICs). Subsequently, 5 or 6 wild-type isolates and 4 or 5 fks mutants of C. albicans, C. glabrata, C. krusei, C. parapsilosis (wild type only), and C. tropicalis were tested (930 MICs). For each strain-plate combination, 98% of the repetitive MICs were within 3 dilutions. The rezafungin modal MICs for the collated C. albicans control strain distributions were 0.016 mg/liter across TC plates but 0.03 mg/liter across UT plates, whereas they were 0.004 mg/liter and 0.016 mg/liter, respectively, for anidulafungin. The difference was most pronounced with Falcon plates and was not observed for C. krusei and C. parapsilosis. Eleven rezafungin MICs for mutants overlapped with the MICs for wild-type isolates (TC plates, n 4; UT plates, n 7). For anidulafungin, five overlaps (all UT plates) were observed. Most overlaps (rezafungin, n 5; anidulafungin, n 3) were caused by fks mutants of C. tropicalis (Fks1, F650F/L) and C. glabrata (Fks2. D666Y; rezafungin, n 2; anidulafungin, n 1). Interlaboratory variation was low. The use of TC plates resulted in lower MICs, particularly for C. albicans and Falcon plates, ad this was more often the case for anidulafungin than for rezafungin. Adoption of TC plates for EUCAST antifungal susceptibility testing would improve interlaboratory reproducibility and the separation of non-wild-type and wild-type strains.
AB - Rezafungin is a new long-acting echinocandin currently in phase 3 development. Epidemiological cutoff values are necessary for breakpoint setting but have not been established due to unexplained interlaboratory MIC variations observed in a prior multicenter study. Here we investigated if the choice of microtiter plates affected the variability when anidulafungin was included as a comparator. Testing by the EUCAST E.Def 7.3.1 reference method using tissue and cell culture-treated polystyrene plates (TC plates) and untreated polystyrene plates (UT plates) from four manufacturers was performed. Six control strains (Candida albicans, n 3; C. krusei, n 2; C. parapsilosis, n 1) were tested (520 MICs). Subsequently, 5 or 6 wild-type isolates and 4 or 5 fks mutants of C. albicans, C. glabrata, C. krusei, C. parapsilosis (wild type only), and C. tropicalis were tested (930 MICs). For each strain-plate combination, 98% of the repetitive MICs were within 3 dilutions. The rezafungin modal MICs for the collated C. albicans control strain distributions were 0.016 mg/liter across TC plates but 0.03 mg/liter across UT plates, whereas they were 0.004 mg/liter and 0.016 mg/liter, respectively, for anidulafungin. The difference was most pronounced with Falcon plates and was not observed for C. krusei and C. parapsilosis. Eleven rezafungin MICs for mutants overlapped with the MICs for wild-type isolates (TC plates, n 4; UT plates, n 7). For anidulafungin, five overlaps (all UT plates) were observed. Most overlaps (rezafungin, n 5; anidulafungin, n 3) were caused by fks mutants of C. tropicalis (Fks1, F650F/L) and C. glabrata (Fks2. D666Y; rezafungin, n 2; anidulafungin, n 1). Interlaboratory variation was low. The use of TC plates resulted in lower MICs, particularly for C. albicans and Falcon plates, ad this was more often the case for anidulafungin than for rezafungin. Adoption of TC plates for EUCAST antifungal susceptibility testing would improve interlaboratory reproducibility and the separation of non-wild-type and wild-type strains.
KW - Antifungal susceptibility testing
KW - Broth microdilution
KW - Candida
KW - Echinocandins
U2 - 10.1128/aac.00659-19
DO - 10.1128/aac.00659-19
M3 - Journal article
C2 - 31285230
AN - SCOPUS:85071232938
SN - 0066-4804
VL - 63
JO - Antimicrobial Agents and Chemotherapy
JF - Antimicrobial Agents and Chemotherapy
IS - 9
M1 - e00659-19
ER -