Comparison of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Etest Methods with the CLSI Broth Microdilution Method for Echinocandin Susceptibility Testing of Candida Species

Abstract

The antifungal broth microdilution (BMD) method of the European Committee on Antibiotic Susceptibility Testing (EUCAST) and the Etest agar diffusion method were compared with the Clinical and Laboratory Standards Institute (CLSI) BMD method M27-A3 for anidulafungin, caspofungin, and micafungin susceptibility testing of 133 clinical isolates of Candida species. The isolates were characterized for the presence or absence of fks1 and/or fks2 gene mutations and included 34 isolates of C. glabrata (4 mutant strains), 32 of C. albicans (1 mutant strain), 25 of C. parapsilosis, 19 of C. guilliermondii, 12 of C. tropicalis (2 mutant strains), and 11 of C. krusei. Excellent essential agreement (EA; within 2 dilutions) between the CLSI and EUCAST and CLSI and Etest MIC results was observed. The overall EA between the EUCAST and CLSI results ranged from 89.5% (caspofungin) to 99.2% (micafungin), whereas the EA between the Etest and CLSI results ranged from 90.2% (caspofungin) to 93.2% (anidulafungin). The categorical agreement (CA) between methods for each antifungal agent was assessed using previously determined epidemiological cutoff values (ECVs). Excellent CA (>90%) was observed for all comparisons between the EUCAST and CLSI results with the exceptions of C. glabrata and caspofungin (85.3%) and C. krusei and caspofungin (54.5%). The CA between the Etest and CLSI results was also excellent for all comparisons, with the exception of C. krusei and caspofungin (81.8%). All three methods were able to differentiate wild-type (WT) strains from those with fks mutations. With anidulafungin as the test reagent, the CLSI method identified 5 of 7 mutant strains, whereas the EUCAST method and the Etest identified 6 of 7 mutant strains. With either caspofungin or micafungin as the test reagent, the CLSI method identified all 7 mutant strains and the EUCAST method identified 6 of 7 mutant strains. The Etest identified all 7 mutant strains using caspofungin as the reagent. All three test methods showed a high level of agreement and of ability to distinguish fks mutant strains of Candida species from WT strains using each of the echinocandins.

Molecular Characterization of Candida parapsilosis Species Complex in Niches of the Oral Cavity in a Cohort of Patients from Argentina with Different Oral and Dental Clinical Manifestations

“…Recent studies have described a precise mutation in the glucan synthase (FKS) gene in the parapsilosis species complex, which may well explain this observation. FKS gene mutations have been shown to be associated with resistance to CASPO, which was demonstrated by the increase in MIC values in mutant isolates compared with those non-mutant or wild-type [23,24]. Unlike the results obtained for CASPO, all 19 strains were susceptible to MICA, and MIC 50 and MIC 90 coincided regarding this drug, despite being lower than that reported by other authors like Miranda et al [2] and Tosun et al [7].…”

A Novel Flucytosine-Resistant Yeast Species, Candida pseudoaaseri, Causes Disease in a Cancer Patient

“…The results for the single antifungal agents were comparable, independent of the system that was used (CLSI reference method, Etest, Vitek 2, or Micronaut). It is known that the Etest correlates well with the CLSI reference method for determining the susceptibility of Candida isolates (3,4,5,11,34) and that the results from the YST card of Vitek 2 have a good correlation with the results from the standard method (9,11,36,37). In contrast to both C. aaseri strains, VK065094…”

Molecular identification and antifungal susceptibility profiles of Candida parapsilosis complex species isolated from culture collection of clinical samples

“…Recent works have described a functional point mutation in the glucan synthase (FKS) gene of the C. parapsilosis complex species, which may explain this observation (46) (47) . FKS gene mutations have been shown to be associated with resistance to CAS, as demonstrated by increases in MICs in mutant isolates compared with those of wild-type isolates (48) (49) (50) . In summary, our study reported the first molecular identifi cation of C. parapsilosis complex species in State of Goiás, Brazil.…”