Abstract:

Objective To evaluate the feasibility and clinical significance of applying MALDI SepsityperTM Kit and MicroflexTM LT matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MSK-MS method) to direct identification of microorganisms in positive blood culture specimens. Methods From March to August 2014, both MSK-MS method and traditional blood culture identification method were adopted to identify microorganisms in positive blood culture specimens collected in Xinhua Hospital affiliated to Shanghai Jiao Tong University School of Medicine. If identified results of two methods were inconsistent, the gene sequencing was adopted to make confirmation. Results Among 491 positive blood culture specimens, 462 of them were monobacterial specimens and 29 of them were polymicrobial specimens. There were a total of 30 genera and 64 species or groups. For monobacterial specimens, the coincidence rates of MSK-MS method for identifying genera and species were 72.5% (335/462) and 76.0% (351/462), respectively. The coincidence rates of MSK-MS method for identifying genera and species of Gram-negative bacteria, Gram-positive bacteria, and Candida were 75.4% (132/175) and 77.7% (136/175), 70.9% (178/251) and 74.9% (188/251), and 75.0% (27/36) and 75.0% (27/36), respectively. For polymicrobial specimens, the coincidence rates for identifying one and two bacteria were 55.2% (16/29) and 20.7% (6/29), respectively. The coincidence rates of MSK-MS method for identifying genera of common clinical bacteria of the bloodstream infection were between 74.2% and 96.9%. The identification time was only 40 min per specimen. Conclusion MSK-MS method can accurately and rapidly identify common bacteria of the bloodstream infection, so as to shorten the time for diagnosing the bloodstream infection and provide evidences for quick and rational use of antibiotics.

Key words: MALDI SepsityperTM Kit, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, blood culture, microorganism