MALDI-TOF MS(VITEK V3.0) For Laboratory Diagnosis Of Filamentous Fungi

BackgroudFilamentous fungi are multicellular fungi composed of mycelium and spores.Traditionally,microbiology laboratory diagnosis of filamentous fungal infection by morphological(including direct microscopy and culture),histopathology,serology and other methods.However,these methods are cumbersome to operate,with harsh culture conditions,long testing cycles,and poor sensitivity and positive rates,which can not timely and accurately diagnose and treat infections caused by the relevant pathogens.With the generation and development of genetic sequence analysis technology,the accurate identification of filamentous fungi is further accelerated.However,although the sequence analysis method is accurate,the test cycle is long and the test cost is high.Therefore,it can not be used as a normal means to identify filamentous fungi.In recent years,clinical microbiology laboratories try to use purely biophysical methods to identify microorganisms,such as matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF MS),greatly shorten the identification of microorganisms,especially in the diagnosis of bacteria and yeasts,but little research has been done on the application of filamentous fungi.On the basis of identification of bacteria,in recent years,microbiologists have tried to use MALDI-TOF MS to identify filamentous fungi and have achieved good identification results.however,at present,there is no consensus on whether different culture conditions and culture time will affect the identification of filamentous fungi.Objective:Filamentous fungi were identified by MALDI-TOF MS(VITEK V3.0)at different culture time points in different culture conditions(temperature,medium),then we can evaluate the culture conditions and culture time on the accuracy of its identification when it was used to identifiy filamentous fungi.Methods:In the experiment,79 strains of filamentous fungi,which were initially identified as morphological methods,were cultured in sabouraud liquid media,sabouraud agar media and chalet agar media,respectively.VITEK MS was used to identify strains in three media at two temperature conditions at different culture time points(48 hours,72 hours,96 hours and 120 hours),subsequent molecular sequencing was used as the"gold standard"to further validate the identification results of mass spectrometry techniques.Thus,it was evaluated whether there is a clinically significant difference in the accuracy of MALDI-TOF MS identification of filamentous fungi under different culture conditions at different culture time points.Results:79 strains were identified by VITEK MS,of which 78 were consistent with the molecular method and only one was unidentified.The Chi-square tests(?~2 test,P=0.05)showed that the culture medium and incubation temperature had no effects on the identification accuracy;however,identification accuracy of the strains in the48-h group was lower than that in other groups.In addition,we found that ribosomal proteins extracted from filamentous fungi can be stored in different environments for at least one week,with their profiles remaining stable and strain identification results showing no change.Conclusions:The MALDI-TOF MS technique can identify filamentous fungi in different kinds of media at 28?and 35?rapidly and accurately,compared to culture for 48 hours,the strains cultured for 72 hours are more conducive to analysis.And compared with morphological methods,using mass spectrometry is more stable.