Abstract: Objective To explore the clinical application value of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for rapid detection of pathogenic bacteria isolated from sterile body fluids after positive reporting of enrichment. 
Methods Four hundred and twelve specimens of sterile body fluids with positive broth culture were collected from Hebei General Hospital. The positive specimens were microscopically examined by smear Gram staining, and inoculated with solid medium for culture. The bacterial membrane grew at 35 ℃ for 4-6 h, and the single colony grew at 35 ℃ for 18-24 h. The VITEK MS was applied to identify the bacterial membrane and the colony respectively, and the results of the mass spectrometry identification of the colony were used as the reference standard to analyze the identification rate of the mass spectrometry identification of the bacterial membrane.  
Results A total of 412 pathogenic strains were identified by VITEK MS (colony), including 212 Gram-positive cocci (51.45%), 172 Gram-negative bacilli (41.75%) and 28 fungal strains (6.80%). Compared with the VITEK MS (colony) identification results, the overall identification compliance rate was 91.50% (377/412) for VITEK MS (membrane), 89.15% (189/212) for Gram-positive cocci and 94.19% (162/172) for Gram-negative bacilli, all with significant differences (χ2=36.553, 24.319, 10.299, P＜0.05). For fungal identification, identification compliance rate was 92.86% (26/28) by VITEK MS (membrane), with no significant difference (χ2=2.074, P=0.150). 
Conclusion The application of MALDI-TOF MS for 4-6 h identification of sterile body fluid specimens after positive reporting can further shorten the identification time of pathogenic bacteria, provide rapid and accurate identification results, and provide an early basis for the diagnosis and treatment of invasive infectious diseases in clinical practice. 

Key words: bacteria, mass spectrometry, sterile body fluids, rapid identification