title: In vitro susceptibility of fluconazole-susceptible and -resistant isolates of Malassezia pachydermatis against azoles.
abstract: OBJECTIVE
  The first aim of this study was to evaluate the in vitro efficacies of fluconazole, ketoconazole, itraconazole and voriconazole on M. pachydermatis growth inhibition. This study also evaluated M. pachydermatis azole cross-resistance, comparing wild clinical isolates and the same isolates with in vitro-induced fluconazole resistance.
  
  
  METHODS
  Two techniques were used: (1) a broth microdilution method based on protocol M27-A3 from the Clinical and Laboratory Standards Institute to determine the minimum inhibitory concentration (MIC) and (2) the Fekete-Forgács method to induce fluconazole resistance in vitro. The isolates were divided into two groups: group 1 included fluconazole-susceptible clinical isolates (n=30) and group 2 contained the same isolates with in vitro-induced fluconazole resistance (n=30).
  
  
  RESULTS
  The two groups exhibited differences in susceptibility (p<0.001). Group 1 isolates were susceptible to azoles: ketoconazole (MIC 0.01-1.0 μg/mL), itraconazole (MIC 0.01-1.0 μg/mL), voriconazole (MIC 0.01-4.0 μg/mL), and fluconazole (MIC 0.01-4.0 μg/mL). Group 2 isolates demonstrated a wider range of MICs to azoles: ITZ (MIC 0.06-64.0 μg/mL), KTZ (MIC 0.25-32.0 μg/mL), VRZ (MIC 2.0-128.0 μg/mL), and FLZ (MIC 64.0-128.0 μg/mL).
  
  
  CONCLUSIONS
  It was shown that FLZ-resistant M. pachydermatis isolates exhibit cross-resistance to other azoles, reinforcing the importance of susceptibility tests as a guide for the therapeutic prescription of antifungals in medical and veterinary mycology.
authors.affiliation: Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Maria (UFSM) 97105-900, Santa Maria, RS, Brazil.
authors.forename: F P K
authors.initials: FP
authors.lastname: Jesus
authors.forename: C
authors.initials: C
authors.lastname: Lautert
authors.forename: R A
authors.initials: RA
authors.lastname: Zanette
authors.forename: D L
authors.initials: DL
authors.lastname: Mahl
authors.forename: M I
authors.initials: MI
authors.lastname: Azevedo
authors.forename: M L S
authors.initials: ML
authors.lastname: Machado
authors.forename: V
authors.initials: V
authors.lastname: Dutra
authors.forename: S A
authors.initials: SA
authors.lastname: Botton
authors.forename: S H
authors.initials: SH
authors.lastname: Alves
authors.forename: J M
authors.initials: JM
authors.lastname: Santurio
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D025141:Drug Resistance, Fungal; D015725:Fluconazole / Q000494:pharmacology*; D017964:Itraconazole / Q000494:pharmacology; D007654:Ketoconazole / Q000494:pharmacology; D008290:Malassezia / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D011743:Pyrimidines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology; D065819:Voriconazole
chemical_list: D000935:Antifungal Agents; D011743:Pyrimidines; D014230:Triazoles; D017964:Itraconazole; D015725:Fluconazole; D065819:Voriconazole; D007654:Ketoconazole