Use of mass spectrometry to identify clinical Fusarium isolates

Abstract number: R2407

Marinach-Patrice C., Lethuillier A., Marly A., Urtizverea I., Brossas J-Y., Gene F., Symoens F., Datry A., Guarro J., Mazier D., Hennequin C.

Fusarium spp. have recently emerged as significant human pathogens. Species identification of these fungi is important both for epidemiologic purposes and for patient management, but conventional identification based on morphologic traits is hindered by major phenotypic polymorphism.

In this study, we subjected 62 isolates belonging to nine Fusarium species to both molecular identification (TEF1 gene sequencing) and MALDI-TOF analysis. Following stringent standardisation, the latter method appeared both reproducible and robust even when various influencing factors such as growth medium, temperature and time of incubation were evaluated. Spectrum comparison with a database of the most frequently isolated species correctly identified 57 isolates. As expected, the four members of species not represented in the database were not identified. Mass spectrometry and molecular identification agreed in 5 of the 6 cases in which morphological and molecular identification disagreed.

In conclusion, the constructed database and the standardised protocol were validated for identification of the most common clinical Fusarium isolates. Uncommon species must now be added to the database. MALDI-TOF yielded results within one hour, at a cost similar to that of the molecular method. MALDI-TOF may also prove useful for identifying other clinically important moulds.