A New Method Aimed to Quickly Identify Pathogen and Drug Susceptibility Test Based on Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry Combined with Flow Cytometry.

Aim: To discuss the significance and applied value in the rapid identification and drug susceptibility test for blood stream infection (BSI) using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) combined with flow cytometry (FCM).

Methods: The bacteria were separated from the positive blood culture bottle using the separation gel-adsorption method system, and then applying MALDI-TOF MS combined with FCM to identify pathogen and drug susceptibility test quickly.

Results: The efficiency of the separation gel-adsorption method for gram-negative bacterium, gram-positive bacteria, and fungi is 71%, 74%, and 88%, respectively. The results of identifying pathogens using MALDI-TOFMS are in agreement with results obtained using VITEK2 (bioMérieux, Marcy l'Etoile, France); both methods can identify 90% of bacteria to species. For fungi, MALDI-TOF MS can identify 75% fungi to species, which is superior to VITEK2, which identifies 60% fungi to species. The results of drug susceptibility test using FCM are almost identical to VITEK2; additionally, the addition of fluorescein diacetate can identify the heterogenic drug-resistant strains.

Conclusions: We can quickly identify pathogen and drug-susceptibility test based on MALDI-TOF MS combined with FCM, which is consistent with traditional methods and can shorten the report time from 36-72 hour to 3 hours. More importantly, these methods are of great significance and clinical importance for the rapid identification of BSI.