Experimental Research Of Bacteria Identification And Homology Analysis By Use Of Matrix-assisted Laser Analysis/Ionization Flight Time Mass Spectrometry

Objective:Toevaluatethefeasibilityofmatrix-assistedlaser desorption/ionization-time of flight mass spectrometry（MALDI-TOF MS）in bacteria identification and drug-resistant bacteria’s homology analysis in clinical laboratory.Methods:Four hundred and forty strains of non-repeated samples were obtained in our hospital from January 2015 to January 2016.Firstly,we took advantage of VITEK 2 automatic microbiological identification&drug sensitive system（traditional biochemical reaction technique）and VITEK MS automatic rapid microbiological mass spectrometer（MALDI-TOF MS technique）to identify these strains,respectively.Then,the inconsistent results were re-confirmed with the ribosomal 16S rRNA gene sequence analysis.Concurrently,to evaluate the advantages of MALDI-TOF MS in turn-around time（TAT）,we collected 95 strains of Klebsiella pneumoniae screened by modified Hodge test（MHT）.By use of multilocus sequence typing（MLST）and Microflex ^TMM mass spectrometer（MALDI-TOF MS technique）,we analyzed bacteria’s homology of the 95 strains respectively.Results:Using the result of VITEK 2 as the reference,the total accuracy rate of the 440 strains identified by VITEK MS was 96.6%at species level,and 99.1%at genus level.The results of 15 inconsistent strains identified by 16S rRNA showed that there were 3 different identification at species level by VITEK MS,and there were 12different identification at species level by VITEK 2（P=0.034）.However,it took nearly8 hours per plant for VITEK 2 comparing 8 hours for VITEK MS to complete the tests.and it took only 1 min per strain.The results of 95 CRKP MLST typing were divided into 9 sequence types,ST11 accounted for 91.6%.The results of cluster analysis obtained by Microflex^TM mass spectrometer were divided into 2 types,5 subtypes.TheⅠb andⅠc had a close relationship,andⅠa andⅠb、Ⅰc had a distant relationship.Conclusion:The above results indicate that MALDI-TOF MS could be applied to identify common bacteria from the clinical departments.The identification ability of MS has more advantageous than traditional biochemical reaction identification.In TAT,MALDI-TOF MS greatly shortened identification time..According to the MLST classification of CRKP,there are 9 sequence types in 95 strains,and the main type of the classification is ST11,which is consistent with the domestic popular investigation report.The results of the MALDI-TOF MS cluster analysis showed that the correlation analysis of 95 strains was more detailed than that of MLST.