Identification Of Enterobacter Sakazakii By MALDI-TOF-MS And Analysis Of Susceptibility On Medicine

Objective:A method using matrix-assisted laser desorption ionization-time of flight mass spectrometry(MALDI-TOF-MS)to identify 38 wild Enterobacter sakazakii,2 reference strains and Enterobacter cloacae were evaluated.Moreover the common and difference of mass spectrogram between all the strains were investigated.The dendrogram for all strains was analysed,which unite the source and kinds of strains,with the purpose of correlation between them.The effect on the MALDI-TOF-MS results of the strains on different culture medium were evaluated also.The susceptibility of 4 strains were identified.Methods:The accuracy of MALDI-TOF-MS were identified according to biochemical results.Identification of Enterobacter sakazakii and Enterobacter by MALDI-TOF-MS were done.The affiliation for 40 strains mass spectrum was also researched.Furthermore dendrogram of 40 strains by MALDI-TOF-MS was evaluated,with the purpose to research the correlation between result and source?kind of strain.The analysis of susceptibility were identified by Phoenix 100.Results:The identification results by MALDI-TOF-MS were 2.0-2.3 score for all the 40 strains with very high accuracy which were also consitent with biochemical results.Enterobacter sakazakii and Enterobacter cloacae can be separated accurately by MALDI-TOF-MS even the affiliation is very close between them.The quasi-molecular ions of 40 strains were very high at 5745 m/z.About 95 percent of 40 strains got quasi-molecular ion at 2871?4740?6260?8288?9488m/z.From the dendrogram,5 kinds of MALDI-TOF-MS types were appeared at distance level of 0.5.From the dendrogram,5 kinds of MALDI-TOF-MS types were appeared at distance level of 0.5.The correlation between dendrogram and source?kind of strain were unconspicuous.5 strains of Enterobacter sakazakii were susceptive on Amoxicillin-clavulanate?Ampicillin and cefazolin.Conclusion:MALDI-TOF-MS has ability to identify Enterobacter sakazakii,reference strains and Enterobacter cloacae correctly and exactly in this study.The quasi-molecular ions in most of the strains in this study at 2871?4740?5745?6260?8288?9488m/z could be a signal one for Enterobacter sakazakii.40 strains contained 5 kinds of MALDI-TOF-MS types were appeared at distance level 0.5 for the dendrogram,the law between strains different classes strains needs further study.More study about the correlation between dendrogram and source and kinds of all strains of Enterobacter sakazakii is necessary.5 strains of Enterobacter sakazakii were susceptive on Amoxicillin-clavulanate,Ampicillin and cefazolin by the Phoenix 100 automated microbiology system,the correlation between susceptibility and source of Enterobacter sakazakii need more research.