title: High prevalence of azole resistance in Aspergillus fumigatus isolates from high-risk patients.
abstract: OBJECTIVE
  Aspergillus fumigatus is the leading cause of invasive aspergillosis. Adequate treatment is complicated by an increase in azole resistance. Here, the incidence of voriconazole, posaconazole and itraconazole resistance in clinical isolates from high-risk patients from either the haematology ward or the ICU of the University Medical Center Utrecht in the period 2011-13 is analysed. Putative clonality of resistant strains was tested through cyp51A and microsatellite typing.
  
  
  METHODS
  Primary A. fumigatus isolates from 105 patients were collected by an unbiased routine diagnostic-driven approach and phenotypically tested for azole susceptibility. Of the 105 isolates, 5 were from patients with a proven invasive A. fumigatus infection, 48 were from patients with a probable invasive A. fumigatus infection and 52 were from patients with non-invasive infections. Real-time PCR and cyp51A gene and strain typing were performed.
  
  
  RESULTS
  Twenty-one out of 105 (20.0%) isolates were resistant to at least one of the three clinical azoles and 17/105 (16.2%) isolates were resistant (MIC >2 mg/L) to voriconazole, the empirical drug of choice for treatment of aspergillosis. There was a striking difference in the prevalence of triazole resistance, with 15.9% resistant isolates (25.0% in proven/probable patients) in the haematology population and 4.5% (10% in proven/probable) in the ICU. While the majority of isolates with elevated MICs of voriconazole were cyp51A related (17/23), both microsatellite and cyp51A sequence typing argue against clonal spread of resistant strains.
  
  
  CONCLUSIONS
  This study reveals a high incidence of voriconazole resistance (16.2%) in A. fumigatus in high-risk patients. Our data stress the need for laboratory detection of azole resistance prior to treatment.
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Fuhren
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: W S
authors.initials: WS
authors.lastname: Voskuil
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: C H E
authors.initials: CH
authors.lastname: Boel
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: P J A
authors.initials: PJ
authors.lastname: Haas
authors.affiliation: Department of Medical Microbiology and Infectious Diseases, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: F
authors.initials: F
authors.lastname: Hagen
authors.affiliation: Department of Medical Microbiology and Infectious Diseases, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: J F
authors.initials: JF
authors.lastname: Meis
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands h.kusters@umcutrecht.nl.
authors.forename: J G
authors.initials: JG
authors.lastname: Kusters
mesh_terms: D000046:Academic Medical Centers; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000935:Antifungal Agents / Q000494:pharmacology*; D001228:Aspergillosis / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D001232:Aspergillus fumigatus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D001393:Azoles / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D003428:Cross Infection; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D004271:DNA, Fungal; D025141:Drug Resistance, Fungal; D005260:Female; D005656:Fungal Proteins / Q000235:genetics; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D018895:Microsatellite Repeats; D008875:Middle Aged; D058889:Molecular Typing; D010802:Phylogeny; D015995:Prevalence; D055815:Young Adult
chemical_list: D000935:Antifungal Agents; D001393:Azoles; D004271:DNA, Fungal; D005656:Fungal Proteins; D003577:Cytochrome P-450 Enzyme System; C465526:cytochrome P-450 CYP51A, Aspergillus