Identification of Demodex Hominis using Matrix-Assisted Laser Desorption / Ionization Time of Flight Mass Spectrometry

Abstract

This study investigated the application of Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) to identify Demodex hominis at various developmental stages and establish a reproducible spectral database for Demodex hominis. The profile spectra of Demodex hominis were obtained by VITEK® Mass Spectrometry (MS) and the database was created by the SARAMIS™ super spectra tool. In the validation study and blind test, correct identification at the species and development stage level is based on SARAMIS™ software analysis. Consistent and reproducible MS profiles were obtained in 28 specimens. A spectrum database, including 4 super spectra, revealed 15 discriminating mass peaks. Peaks 4304.7 and 8609.8 were specific peaks for Demodex hominis. Peaks 3346.8 and 5236.6 are shown in adult Demodex brevis spectra. Similarly, peaks 3788.2 and 7673.3 emerged in the larva Demodex brevis. Peaks 4109.6, 5383.2, and 7518.3 presented in adult Demodex follicurolum spectra. Peak 4696.8 appeared only in larva Demodex follicurolum. In the blind test, 44 of the 48 demodex specimens in the target development stage were correctly identified. These findings highlight that protein profiling utilizing MALDI-TOF-MS represents an efficient and reliable methodology for the identification of Demodex hominis across both species and developmental stages. An initial database comprising the spectral data of the two Demodex hominis species in China has been established.