Background: Aspergillus species are the most common and feared agents of invasive fungal
infections because of their high morbidity and mortality rates. Nowadays, Aspergillus cryptic species
emerged as frequent strains isolated from clinical samples. Classic methods, based on morphology,
are not able to identify cryptic species, whereas common molecular techniques, while effective, are
still too costly for routine use and need considerable time for sample preparation. As these limitations
may be overcome by Matrix assisted laser desorption ionization-time of flight mass spectrometry
(MALDI-TOF) identification methodology, it was decided to verify whether it could be applied to such
Material/methods: 51 Aspergillus strains (31 clinical, mainly respiratory samples, and 20 air
environmental sources), previously identified by classical morphological and molecular (ß-tubulin and
calmodulin regions) methods, were prepared using the Moulds VITEK® MS kit (CE-IVD) and analyzed
by MALDI-TOF methodology, using VITEK® MS with the Knowledge Base v3.0 library (CE-IVD).
Results: In what the 31 clinical isolates concerns, 29 (93.5%) were identified by VITEK® MS: 25 to
the species level (8 A. fumigatus, 8 A. flavus/oryzae, 4 A. lentulus, 3 A. terreus complex, 1 A .niger
complex and 1 A. nidulans) and 4 inside the complex (3 A. welwitschiae, Nigri complex and 1 A.
thermomuthatus, Fumigati complex). One A. lentulus and one A. felis were not identified. Concerning
the 20 air samples isolates, 10 were correctly identified by VITEK® MS. Nine species (A. alabamensis,
A. tubingensis, A. luchuensis, A. nomius, A. parasiticus, A. felis, A. udagawae, A. giganteus and A.
delacroxii) previously categorized as cryptic and one A. nidulans were not identified. Apart from A.
nidulans none of the other species are present in the current clinical Knowledge Base.
Conclusions: The rapid identification of Aspergillus spp., particularly their cryptic species, important
for efficient diagnosis and patient management, was accomplished by VITEK MS®. The results of
MALDI analysis of clinical isolates evidence a good performance, similarly to a previous study (1). In
contrast, air samples analysis, where unusual cryptic species were isolated, was less accurate,
emphasizing the value of continued VITEK MS® Knowledge Base update.
1. McMullen AR, Wallace MA, Pincus DH, Wilkey K, Burnham CA. Evaluation of the VITEK MS Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry System for Identification of Clinically Relevant Filamentous Fungi. J Clin Microbiol. 2016 Aug;54(8):2068-73. doi: 10.1128/JCM.00825-16.
We thank bioMérieux Portugal the offer of Moulds VITEK® MS kit.
Full conference title:
- ECCMID 27th (2017)