title: Comparison of three statistical methods for establishing tentative wild-type population and epidemiological cutoff values for echinocandins, amphotericin B, flucytosine, and six Candida species as determined by the colorimetric Sensititre YeastOne method.
abstract: The Sensititre YeastOne (SYO) method is a widely used method to determine the susceptibility of Candida spp. to antifungal agents. CLSI clinical breakpoints (CBP) have been reported for antifungals, but not using this method. In the absence of CBP, epidemiological cutoff values (ECVs) are useful to separate wild-type (WT) isolates (those without mechanisms of resistance) from non-WT isolates (those that can harbor some resistance mechanisms), which is the goal of any susceptibility test. The ECVs for five agents, obtained using the MIC distributions determined by the SYO test, were calculated and contrasted with those for three statistical methods and the MIC(50) and modal MIC, both plus 2-fold dilutions. The median ECVs (in mg/liter) (% of isolates inhibited by MICs equal to or less than the ECV; number of isolates tested) of the five methods for anidulafungin, micafungin, caspofungin, amphotericin B, and flucytosine, respectively, were as follows: 0.25 (98.5%; 656), 0.06 (95.1%; 659), 0.25 (98.7%; 747), 2 (100%; 923), and 1 (98.5%; 915) for Candida albicans; 8 (100%; 352), 4 (99.2%; 392), 2 (99.2%; 480), 1 (99.8%; 603), and 0.5 (97.9%; 635) for C. parapsilosis; 1 (99.2%; 123), 0.12 (99.2%; 121), 0.25 (99.2%; 138), 2 (100%; 171), and 0.5 (97.2%; 175) for C. tropicalis; 0.12 (96.6%; 174), 0.06 (96%; 176), 0.25 (98.4%; 188), 2 (100%; 209), and 0.25 (97.6%; 208) for C. glabrata; 0.25 (97%; 33), 0.5 (93.9%; 33), 1 (91.9%; 37), 4 (100%; 51), and 32 (100%; 53) for C. krusei; and 4 (100%; 33), 2 (100%; 33), 2 (100%; 54), 1 (100%; 90), and 0.25 (93.4%; 91) for C. orthopsilosis. The three statistical methods gave similar ECVs (within one dilution) and included ≥ 95% of isolates. These tentative ECVs would be useful for monitoring the emergence of isolates with reduced susceptibility by use of the SYO method.
authors.affiliation: Unidad de Microbiología Experimental, Centro de Investigación, Hospital La Fe, Valencia, Spain. canton_emi@gva.es
authors.forename: Emilia
authors.initials: E
authors.lastname: Cantón
authors.forename: Javier
authors.initials: J
authors.lastname: Pemán
authors.forename: David
authors.initials: D
authors.lastname: Hervás
authors.forename: Carmen
authors.initials: C
authors.lastname: Iñiguez
authors.forename: David
authors.initials: D
authors.lastname: Navarro
authors.forename: Julia
authors.initials: J
authors.lastname: Echeverría
authors.forename: José
authors.initials: J
authors.lastname: Martínez-Alarcón
authors.forename: Dionisia
authors.initials: D
authors.lastname: Fontanals
authors.forename: Bárbara
authors.initials: B
authors.lastname: Gomila-Sard
authors.forename: Buenaventura
authors.initials: B
authors.lastname: Buendía
authors.forename: Luis
authors.initials: L
authors.lastname: Torroba
authors.forename: Josefina
authors.initials: J
authors.lastname: Ayats
authors.forename: Angel
authors.initials: A
authors.lastname: Bratos
authors.forename: Ferran
authors.initials: F
authors.lastname: Sánchez-Reus
authors.forename: Isabel
authors.initials: I
authors.lastname: Fernández-Natal
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects* / Q000302:isolation & purification; D002177:Candidiasis / Q000382:microbiology; D054714:Echinocandins / Q000494:pharmacology*; D005437:Flucytosine / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D015233:Models, Statistical; D009172:Mycology / Q000379:methods*
chemical_list: D000935:Antifungal Agents; D054714:Echinocandins; D000666:Amphotericin B; D005437:Flucytosine