Triazole resistance in Aspergillus fumigatus: recent insights and challenges for patient management.

BACKGROUND: Triazole resistance in Aspergillus fumigatus is widespread and threatens first-line triazole therapy in patients with Aspergillus diseases. OBJECTIVES: To give an overview of the microbiology, epidemiology and clinical significance of triazole resistance in aspergillosis. SOURCES: PubMed search for articles on resistance in Aspergillus species. CONTENT: Triazoles are not mutagenic but select resistance when spontaneous mutations occur that are better able to proliferate in the triazole-containing environment. The major target for resistance mutations involves the Cyp51A gene, encoding an enzyme involved in cell wall synthesis. Triazole-resistance selection environments include patient treatment and organic matter containing triazole fungicide residues. Reported resistance frequencies vary widely between countries and hospitals, and resistance significantly complicates the diagnosis and treatment of Aspergillus diseases. Cultures may harbour various resistance phenotypes and multiple colonies must be analysed to detect resistance. PCR tests have become available for resistance detection in culture-negative patients, but show limited sensitivity. Individuals with triazole-resistant invasive aspergillosis have a 21% higher day-42 mortality compared with triazole-susceptible infection, and to prevent excess mortality resistant cases require first-line therapy that covers resistance. The recent ESCMID-ECMM-ERS Aspergillus guideline recommends resistance testing in A. fumigatus and local resistance surveillance. If resistance rates exceed 10% liposomal amphotericin B or triazole and echinocandin first-line therapy should be considered. IMPLICATIONS: Triazole resistance significantly complicates the management of aspergillosis and multidisciplinary research from a 'One-health' perspective is required to retain the triazole class for medical use.

Epidemiology of invasive aspergillosis and triazole-resistant Aspergillus fumigatus in patients with haematological malignancies: a single-centre retrospective cohort study.

Objectives: To investigate the epidemiology and clinical relevance of triazole resistance among patients undergoing treatment for haematological malignancies who are at risk of invasive aspergillosis (IA). Methods: This was a retrospective cohort study for which the records of consecutive patients given chemotherapy for AML or myelodysplastic syndrome (MDS) or who had received an allogeneic HSCT from 2006 to 2012 were reviewed for IA. Triazole resistance was detected by the VIPcheck™ screening method and confirmed by determining the MIC by EUCAST methodology. Results: A total of 432 patients were included, comprising 182 (42.1%) patients who had undergone chemotherapy for AML or MDS, and 250 (57.9%) patients who had undergone an allogeneic HSCT. Probable or proven IA was diagnosed in 36 cases (8.3%, 95% CI 6.0%-11.4%). Of these, 12 (33.3%) were based on recovery of Aspergillus fumigatus from sputum, bronchoalveolar lavage or biopsy, and triazole resistance was found in 2 instances. A. fumigatus was also recovered from one or more specimens from 13 patients without probable or proven IA. Triazole resistance was documented for three patients. The survival rate of patients with IA caused by voriconazole-resistant isolates could not be assessed. Conclusions: The overall frequency of voriconazole-resistant IA among patients at high risk was low. However, the rate of triazole resistance may have been underestimated by the low detection rate based on recovery of A. fumigatus. Alternative diagnostic tests, such as PCR-based assays, may prove better at detecting IA due to triazole-resistant A. fumigatus.