title: Activity of MK-3118, a new oral glucan synthase inhibitor, tested against Candida spp. by two international methods (CLSI and EUCAST).
abstract: OBJECTIVE
  To evaluate the activity of the orally bioavailable enfumafungin derivative MK-3118 and comparator antifungal agents tested against a collection of 113 clinical isolates of Candida spp. using CLSI and EUCAST broth microdilution (BMD) methods.
  
  
  METHODS
  Candida spp. isolates (n=113) were tested by CLSI and EUCAST methods. The collection contained 29 Candida albicans, 29 Candida glabrata, 21 Candida tropicalis, 15 Candida parapsilosis and 19 Candida krusei, including azole- and echinocandin-resistant isolates. CLSI and EUCAST MIC endpoints of 50% and 100% inhibition were determined using visual reading at 24 and 48 h of incubation and spectrophotometric reading at 24 h of incubation, respectively.
  
  
  RESULTS
  MK-3118 CLSI MIC results ranged from 0.06 to 16 mg/L depending on species, duration of incubation and endpoint criteria (EC) used. Comparison of CLSI and EUCAST following 24 h of incubation and either 50% or 100% inhibition revealed an essential agreement (EA; ± 2 doubling dilutions) of 99.1% using the 50% inhibition EC and 93.2% using the 100% inhibition EC. MK-3118 (24 h of incubation and 50% EC) was active against all the species tested and displayed similar potency to caspofungin (using CLSI BMD) against C. albicans (MIC90, 1 and 2 mg/L, respectively), C. tropicalis (1 and 1 mg/L, respectively), C. parapsilosis (0.5 and 0.5 mg/L, respectively) and C. krusei (2 and 1 mg/L, respectively), but was 8-fold more potent than caspofungin against C. glabrata strains (MIC90, 2 and 16 mg/L, respectively). MK-3118 was active against fluconazole-resistant strains as well as caspofungin-resistant strains with documented fks mutations.
  
  
  CONCLUSIONS
  MK-3118 was documented to have potent in vitro activity against Candida spp. when tested by both CLSI and EUCAST BMD methods, with the highest overall EA (99.1%) obtained when MK-3118 MIC results were read after 24 h of incubation using a partial inhibition EC (50%).
authors.affiliation: JMI Laboratories, North Liberty, IA, USA. michael-pfaller@uiowa.edu
authors.forename: Michael A
authors.initials: MA
authors.lastname: Pfaller
authors.forename: Shawn A
authors.initials: SA
authors.lastname: Messer
authors.forename: Mary R
authors.initials: MR
authors.lastname: Motyl
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
authors.forename: Mariana
authors.initials: M
authors.lastname: Castanheira
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects* / Q000302:isolation & purification; D002177:Candidiasis / Q000382:microbiology; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors*; D006027:Glycosides / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D013997:Time Factors; D014315:Triterpenes / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D006027:Glycosides; D014315:Triterpenes; C569338:ibrexafungerp; D005964:Glucosyltransferases; C040232:glucan synthase