Quality control in culture collections: Confirming identity of filamentous fungi by MALDI-TOF MS

• Performance of MALDI-TOF MS reached 84% of correct identification at species level.
• MALDI-TOF MS is more efficient in detecting historical misidentifications.
• MALDI-TOF MS is a valuable method to support and speed up identity controls.
• A workflow including MALDI-TOF MS is proposed to objectify identity controls.

In culture collections, strains are controlled after preservation to guarantee their viability, purity and identity. For filamentous fungi, the identity is traditionally verified by performing morphological analyses with the support of DNA sequencing if required. These methods are particularly time-consuming and require extensive knowledge of mycology. In this study, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was evaluated as an alternative method for fast, robust and objective identity controls in the routine work of the BCCM/IHEM fungal collection. A total of 481 controls were carried out using mass spectrometry and compared to the results obtained by the conventional procedure. The overall performance of the MALDI-TOF MS reached 84% of correct identification at species level. Moreover, misidentification at entry in the collection was put in evidence for 14 strains by mass spectrometry and confirmed by DNA sequencing. Out of these, only eight were detected by the traditional method. Considering these results, a workflow combining MALDI-TOF MS, microscopy and genetic analyses is proposed to speed up and objectify identity controls in fungal culture collections.