In Vitro Susceptibility of Respiratory Isolates of Aspergillus Species to Itraconazole and Amphotericin B. Acquired Resistance to Itraconazole

Scand J Infect Dis. 1997;29(5):509-12. doi: 10.3109/00365549709011864.


122 Aspergillus strains were isolated from respiratory specimens from 80 patients. Aspergillus fumigatus was the most common species, constituting 88% of the isolates. Susceptibility testing by the NCCLS broth macrodilution procedure revealed that the minimal inhibitory concentration for 50% of the strains (MIC50) was 0.25 mg/l for itraconazole and 0.5 mg/l for amphotericin B. The MIC90 was 1 mg/l for both drugs. To our knowledge, no cases of in vitro resistance during long-term itraconazole use in treatment of Aspergillus infection have been documented. We identified 3 patients infected with A. fumigatus strains that acquired in vitro resistance to itraconazole during prolonged therapy. This finding supports the importance of susceptibility testing.

MeSH terms

  • Amphotericin B / pharmacology*
  • Antifungal Agents / pharmacology*
  • Aspergillosis / drug therapy
  • Aspergillus / drug effects*
  • Drug Resistance, Microbial
  • Humans
  • Itraconazole / pharmacology*
  • Microbial Sensitivity Tests
  • Respiratory Tract Infections / drug therapy


  • Antifungal Agents
  • Itraconazole
  • Amphotericin B