A total of 491 cases with positive blood culture were collected. The bacteria were enriched and purified directly from blood culture bottle by separation gel tube, and then the bacteria were identified by MALDI-TOF MS. Traditional culture and identification processes were performed simultaneously, and the cultured pure colonies were identified by Vitek 2 Compact automated microbial analysis system (Vitek 2 Compact). The identification of bacterial isolates by MALDI-TOF MS was compared with that of traditional biochemical testing, and discrepancies were resolved by gene sequencing.

A total of 491 positive cultures were determined, representing 30 genera and 64 species or groups. The method demonstrated 73.6% and 3.7% concordance to species and genus identification rates in monomicrobial culture (462 cases). The correct species and genus identification rates were 84.0%(147 cases) and 2.9%(5 cases) in Gram-negative bacteria(175 cases), were 75.3%(189 cases) and 4.4%(11 cases) in Gram-positive bacteria(251 cases), and were 19.4%(7 cases) and 2.8% (1 case) in Candida species(36 cases). In 29 cases of complex bacterial infection, the correct species and genus identifications rates in one of the multiple bacteria were 79.3% (23 cases) and 10.3% (3 cases). Species identification rates of bloodstream infection with common pathogens were 83.3%-96.9%.

This separation gel tube-based MALDI-TOF MS for the direct identification of blood culture pathogens is established. The identification rate of common pathogens in bloodstream infection by MALDI-TOF MS is higher compared with that by traditional culture identification processes. In addition, it is rapid, easy and cost-effective, and it is a recommendable method for clinical microbiology laboratories.