Abstract:

Objective To improve the direct identification of microorganisms in positive blood culturing by matrix-assisted laser desorption ionization-time of flight mass spectrometry （MALDI-TOF MS） with the pretreatment of sodium dodecyl sulfate（SDS）. Methods A total of 378 blood culturing bottles were collected from March to September in 2016. Microorganisms were enriched and purified directly from blood culturing bottles by separation gel tube,washed by SDS,and then the samples were directly identified by MALDI-TOF MS. Traditional culturing and identification processes were performed simultaneously to be a reference. The accuracy of identification by MALDI-TOF MS with or without SDS pretreatment was compared. Results A total of 87 blood culturing samples without SDS washing were determined,and there were 83 cases of single strains and 4 cases of complex strains. The accurate species identification rate was 73.5%. The remaining 286 samples washed by SDS identified 277 cases of single strains and 9 cases of complex strains,and the accurate species identification rate was 82.7%. The identification rate for Gram-positive strains increased from 65.7% to 90.5%. Improvement was more frequent in yeast identification from 11.1% to 50.0% with statistical significance（P<0.05）. Conclusions The preparation method,based on SDS washing,improves the identification rate of positive blood culturing directly by MALDI-TOF MS. It is easy-to-operation,time-saving and low-cost,which could be promoted in clinical microbiology laboratories.

Key words: Sodium dodecyl sulfate, Matrix-assisted laser desorption ionization-time of flight mass spectrometry, Blood culturing, Direct identification