title: Rapid method for testing the susceptibility of Aspergillus fumigatus to amphotericin B, itraconazole, voriconazole and posaconazole by assessment of oxygen consumption.
abstract: OBJECTIVE
  Antifungal stress conditions affect fungal germination and growth. The assessment of oxygen consumption resulting from the challenge of Aspergillus fumigatus conidia with antifungal agents might be predictive of the susceptibility of this species to the agents evaluated.
  
  
  METHODS
  The antifungal susceptibilities of A. fumigatus to amphotericin B, itraconazole, voriconazole and posaconazole were evaluated for 20 clinical strains by two methods: the rapid assessment of oxygen consumption and the CLSI M38-A2 microdilution method. For the determination of oxygen consumption, conidia were suspended in RPMI 1640 medium with two different concentrations of each antifungal drug (0.25 and 2 mg/L); the oxygen consumption was quantified in a biological oxygen monitor.
  
  
  RESULTS
  A. fumigatus strains showed a wide spectrum of amphotericin B, itraconazole and voriconazole MICs (0.06 to >16 mg/L), but posaconazole MICs ranged from 0.06 to 1 mg/L. Distinct respiratory kinetics, which corresponded to the MIC results, were found. Strains with the highest itraconazole and voriconazole MICs grew faster, undoubtedly consuming the oxygen available in the liquid medium. The reproducibility of this new method was adequate (87%), as well as the agreement with the CLSI method (85%).
  
  
  CONCLUSIONS
  Although the potential of this new and rapid method (4-8 versus 48 h CLSI method) for evaluating the susceptibility of A. fumigatus to the antifungal agents has been demonstrated by these preliminary results, further collaborative studies with more isolates should better assess the value of this methodology for testing isolates in the clinical laboratory.
authors.affiliation: Department of Microbiology, Faculty of Medicine, University of Porto, Porto, Portugal.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Araujo
authors.forename: Isabel
authors.initials: I
authors.lastname: Coutinho
authors.forename: Ana
authors.initials: A
authors.lastname: Espinel-Ingroff
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D001228:Aspergillosis / Q000382:microbiology; D001232:Aspergillus fumigatus / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D008826:Microbial Sensitivity Tests / Q000379:methods; D010101:Oxygen Consumption; D015203:Reproducibility of Results
chemical_list: D000935:Antifungal Agents; D003470:Culture Media