Does monitoring cyp51A-mediated triazole resistance in Aspergillus fumigatus by pyrosequencing lead to patient benefit?

Author:

L Novak-Frazer1,2, D Hassan1, S Hill1,2, CB Moore1,2, R Rautemaa-Richardson1,2,3,
MD Richardson1,2

Author address:

1NHS Mycology Reference Centre Manchester, Manchester University NHS Foundation Trust Wythenshawe Hospital, Manchester, UK
2Division of Infection, Immunity and Respiratory Medicine, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
3Department of Infectious Diseases and the National Aspergillosis Centre, Manchester University NHS Foundation Trust Wythenshawe Hospital, Manchester, UK

Full conference title:

9th Advances Against Aspergillosis

Date: 27 February 2020

Abstract:

Purpose: The global trend of rising triazole resistance rates in Aspergillus fumigatus requires close monitoring. The high volume culture (HVC) procedure developed at the NHS Mycology Reference Centre Manchester (MRCM) has improved culture positivity, thereby allowing EUCAST susceptibility testing to monitor resistance. However, as the failure rate is still significant, a molecular approach is warranted. Commercial assays testing for the environmental mutations (e.g. TR34/L98H) do not detect cyp51A mutations resulting from the pressure of long courses of azole treatment experienced by patients with progressive, chronic conditions. As a result of this limited coverage of polymorphisms, we adopted a pyrosequencing approach to monitor patients with chronic pulmonary aspergillosis (CPA) and/or allergic bronchopulmonary aspergillosis (ABPA), who demonstrated signs of clinical failure: those who demonstrated good drug levels but were persistently positive by Aspergillus spp. qPCR and remained symptomatic. Following over two years of testing, we assessed the impact of monitoring triazole resistance on patient outcome.

Methods: To assess whether this molecular approach benefited patient care, we performed a retrospective audit over a 26-month period, between July 2017 and September 2019, at MRCM and the UK National Aspergillosis Centre (NAC). We reviewed the records of confirmed CPA and ABPA patients to assess the impact of susceptibility and/or pyrosequencing results on patient care. Hospital and laboratory databases were searched for patient history and well-being scores, laboratory findings and if/when the susceptibility or pyrosequencing results triggered a change in antifungal drug therapy.

Results: Two hundred patients, who had at least one sample analysed by pyrosequencing, were considered for review alongside two hundred patients who did not have the test; these patients were selected randomly but matched as closely as possible to the latter cohort. For patients whose samples underwent pyrosequencing, there was resistance data available at twice the frequency of those patients for whom only culture was available. Moreover, resistance was identified by pyrosequencing in up to a quarter of culture negative samples. If pyrosequencing had not been used in these patients, 54 resistant cases would have been missed. Identification of the environmental TR34/L98H mutation was similar in both cohorts. Importantly, resistance was recognised by pyrosequencing before HVC results were available in up to one fifth of cases.

 

Conclusion: Pyrosequencing had a higher sensitivity for detecting triazole resistance than culture-based susceptibility testing. The technology allowed for prompt recognition of resistant organisms and the selection of appropriate antifungal treatment. The detailed impact on improved patient outcomes and better antifungal stewardship will be discussed.

Abstract Number: 172

Conference Year: 2020

Link Conference abstract: 

AAAM 2020

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