During October-December, 2018, the EUCAST AFST committee has experienced variable performance of two batches of VipCheck plates (screening plate for detection of azole resistance in Aspergillus fumigatus).
In brief, wild type (wt) clinical A. fumigatus isolates and the susceptible quality control strain A. fumigatus ATCC 204305 grew on an unacceptable number of itraconazole wells (batches #144914 and #145151). These isolates were confirmed wt and susceptible by EUCAST E.Def 9.3.1 reference testing and target gene sequencing, and failed to grow on itraconazole in house plates prepared according to E.Def 10.1. The concentration of itraconazole has subsequently been compared in VipCheck plates and in house plates and the results suggest a variable itraconazole concentration to be the cause of the problem. This may lead to erroneus categorization of both susceptible and resistant isolates. It is currently unknown how many batches, and also how many plates in each batch, may be affected. The manufacturer is currently reviewing the protocol for dissolving itraconazole to improve their manufacturing process.
Laboratories are warned against the use of the VipCheck plates until this issue has been resolved.