Identification of lethal Aspergillus at early growth stages based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Delayed and incorrect diagnoses are potential risk factors leading to high mortality of invasive aspergillosis (IA). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to acquire a wide mass spectral range and characterize the early process of asexual sporulation of lethal IA pathogens recovered on agar plates. Proteins were extracted using trifluoroacetic acid and soft ionized using an ultraviolet laser with the assistance of ferulic acid. At the second stage of sporulation with various differentiated structures, there are more specific peaks that can be used to discriminate different Aspergillus species than at the first stage, which features vegetative hyphae. Certain specific peaks are found in different strains of the same species, Aspergillus fumigatus. In addition, the relative standard deviations of the m/z ratios are much smaller than those of the relative intensities in these peaks. Therefore, common lethal Aspergillus species can be identified after short-term cultivation by matching species-specific m/z values.