Application Of MALDI-TOF MS In Homology Analysis And Early Identification Of Carbapenem-resistant Klebsiella Pneumoniae

Part Ⅰ Application in homology analysis of carbapenem-resistant Klebsiella pneumoniae by MALDI-TOF MSObjective : To explore the clinical applicability of matrix assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF-MS)in the analysis of carbapenem-resistant Klebsiella pneumoniae(CRKP).Methods:A total of 150 Klebsiella pneumoniae non repetitive strains were collected from a hospital from December 2019 to December 2020,and CRKP was screened by drug resistance phenotype;The mass spectra of CRKP were collected by MALDI-TOF MS,the similarity and identity masses in SARAMIS software were used to analyze the homology;Using pulsed field gel electrophoresis(PFGE)as reference standard,CRKP were divided into three groups: high,medium and low degree of homology,and MALDI-TOF MS was applied in CRKP homology analysis.Results:55 CRKP strains were screened by drug resistance phenotype;three groups of homology analysis showed that: in the highly homologous group,most of them were distributed in a centralized manner(60%~80%)with similarity>80%,which was consistent with PFGE results;in the moderate homology group,the identity mass value was more than 70%,and the similarity was more than 85%.It showed that the strains were highly concentrated,which was different from the results of PFGE;in the low degree homology group,the identity mass was less than 70%,and the similarity was less than 80%,which was similar to that of PFGE.Conclusion:At present,the SARAMIS software provided by MALDI-TOF MS is only used in high homologous and low homologous strains,which can be used as the primary screening method for analyzing the homology.Part Ⅱ Application in early identification of carbapenem-resistant Klebsiella pneumoniae by MALDI-TOF MSObjective: To investigate the early identification ability of MALDI-TOF MS for carbapenem-resistant Klebsiella pneumoniae.Methods: 150 clinical isolates of Klebsiella pneumoniae from December 2019 to December 2020 were collected.The disk diffusion method was used for drug sensitivity test.The results were in accordance with CLSI M100 30 th standard 2020.PCR method was used as the reference standard for drug resistance screening.The mass spectra of CRKP and carbapenem-sensitive Klebsiella pneumoniae(CSKP)were collected by MALDI-TOF MS.Twenty strains of CRKP and CSKP were selected to establish a Super-spectra library.KPN strains were selected to verify whether they were resistant or not,and the results were judged to be accurate according to the resistant phenotype and PCR method.Results:55 strains of CRKP and 95 strains of CSKP were screened from 150 KPN strains.According to the requirements of the database,the Super-spectra of CRKP and CSKP was established by selecting the mass spectra of CRKP and CSKP.Setting the error value < 0.5,the coincidence rate of CRKP and CSKP was 80%.According to the comparison chart,the characteristic peaks of 4154.4m/z,8310.7m/z,10880.8m/z,3579m/z and 10079.3m/z could be used to distinguish CRKP and CSKP.The accuracy rate of CRKP was 91.43%(32/35)and that of CSKP was 90.67%(68/75).The accuracy rate of KPN to carbapenemase was 90.91%(100/110).Conclusion: The establishment of Super-spectra by MALDI-TOF MS can identify CRKP rapidly,which is helpful to improve the level of clinical diagnosis and treatment and nosocomial infection control.