Performance of VITEK mass spectrometry V3.0 for rapid identification of clinical Aspergillus fumigatus in different culture conditions based on ribosomal proteins

Abstract

Fast and accurate discrimination of Aspergillus fumigatus is significant, since misidentification may lead to inappropriate clinical therapy. This study assessed VITEK mass spectrometry (MS) V3.0 for A. fumigatus identification using extracted fungal ribosomal proteins. A total of 52 isolates preliminarily identified as A. fumigatus by traditional morphological methods were inoculated in three different culture media and cultured at two different temperatures. The specific spectral fingerprints of different culture time points (48, 72, 96, and 120 h) were obtained. Of all strains, 88.5% (46/52) were discriminated as A. fumigatus, while the remaining 11.5% (6/52) produced results inconsistent with morphological analysis. Molecular sequencing, as a reference method for species identification, was used to validate the morphological analysis and matrix-assisted laser desorption/ionization time of flight MS. Chi-square tests (χ² test, P=0.05) demonstrated that the culture medium and incubation temperature had no effects on identification accuracy; however, identification accuracy of the strains in the 48-h group was lower than that in other groups. In addition, we found that ribosomal proteins extracted from A. fumigatus can be stored in different environments for at least 1 week, with their profiles remaining stable and strain identification results showing no change. This is beneficial for medical institutions with no mass spectrometer at hand. Overall, this study showed the powerful ability of VITEK MS V 3.0 in identifying A. fumigatus.

Keywords: Aspergillus fumigatus; MALDI-TOF MS; VITEK MS V 3.0; fungal; identification; matrix assisted laser desorption ionization-time of flight mass spectrometry; ribosomal protein; spectral fingerprints.

Figure 1

Proteins stored at 4°C. Note: The 0 h, 48 h, 72 h, 120 h, and 168 h groups, respectively, are presented from bottom to top.

Figure 2

Proteins stored at −20°C. Note: The 0 h, 48 h, 72 h, 120 h, and 168 h groups, respectively, are presented from bottom to top.

Figure 3

Proteins stored at −80°C. Note: The 0 h, 48 h, 72 h, 120 h, and 168 h groups, respectively, are presented from bottom to top.