Frequency and evolution of Azole resistance in Aspergillus fumigatus associated with treatment failure

Emerg Infect Dis. 2009 Jul;15(7):1068-76. doi: 10.3201/eid1507.090043.


Azoles are the mainstay of oral therapy for aspergillosis. Azole resistance in Aspergillus has been reported infrequently. The first resistant isolate was detected in 1999 in Manchester, UK. In a clinical collection of 519 A. fumigatus isolates, the frequency of itraconazole resistance was 5%, a significant increase since 2004 (p<0.001). Of the 34 itraconazole-resistant isolates we studied, 65% (22) were cross-resistant to voriconazole and 74% (25) were cross-resistant to posaconazole. Thirteen of 14 evaluable patients in our study had prior azole exposure; 8 infections failed therapy (progressed), and 5 failed to improve (remained stable). Eighteen amino acid alterations were found in the target enzyme, Cyp51A, 4 of which were novel. A population genetic analysis of microsatellites showed the existence of resistant mutants that evolved from originally susceptible strains, different cyp51A mutations in the same strain, and microalterations in microsatellite repeat number. Azole resistance in A. fumigatus is an emerging problem and may develop during azole therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Antifungal Agents / therapeutic use*
  • Aspergillosis / drug therapy*
  • Aspergillus fumigatus / drug effects*
  • Aspergillus fumigatus / genetics*
  • Azoles / therapeutic use*
  • Cytochrome P-450 Enzyme System / drug effects
  • Cytochrome P-450 Enzyme System / genetics
  • Disease Progression
  • Drug Resistance, Fungal
  • Evolution, Molecular
  • Fungal Proteins / drug effects
  • Fungal Proteins / genetics
  • Humans
  • Itraconazole / pharmacology
  • Itraconazole / therapeutic use*
  • Pyrimidines / pharmacology
  • Pyrimidines / therapeutic use
  • Treatment Failure
  • Triazoles / pharmacology
  • Triazoles / therapeutic use
  • Voriconazole


  • Antifungal Agents
  • Azoles
  • Fungal Proteins
  • Pyrimidines
  • Triazoles
  • Itraconazole
  • Cytochrome P-450 Enzyme System
  • cytochrome P-450 CYP51A, Aspergillus
  • Voriconazole