分离胶促凝管联合MALDI-TOF MS直接检测血培养阳性细菌

Direct identification of microorganisms from blood culture by MALDI-TOF MS combined with separation gel tube

目的建立用分离胶促凝管联合基质辅助激光解析电离飞行时间质谱（MALDI-TOF MS）直接检测血培养阳性待测菌的方法并评估其鉴定符合率。方法共收集阳性血培养491例,利用分离胶促凝管直接从血培养瓶中富集并提纯菌体,采用MALDI-TOF MS对待测菌进行菌种鉴定,同时对报阳性血培养瓶进行转种培养,纯菌落用Vitek 2 Compact全自动微生物分析系统（简称Vitek 2 Compact）进行鉴定。若两者鉴定结果不一致,则以基因测序结果予以确证。结果 491例阳性血培养瓶鉴定出的待测菌包括30个属和64个种。在462例单菌株感染血培养瓶中,菌株的种、属鉴定符合率分别为73.6%和3.7%。其中175例革兰阴性菌的种、属鉴定率分别为84.0%（147例）和2.9%（5例）;251例革兰阳性菌的种、属鉴定率分别为75.3%（189例）和4.4%（11例）;36例念珠菌的种、属鉴定率分别为19.4%（7例）和2.8%（1例）。在29例复数菌感染血瓶中,鉴定出其中一种细菌的种、属鉴定率分别为79.3%（23例）和10.3%（3例）。血流感染中常见病原菌的菌种鉴定符合率达83.3%～96.9%。结论本研究建立了分离胶促凝管联合MALDI-TOF MS直接检测血培养阳性待测菌的方法,与传统的培养鉴定方法相比,对血流感染中主要病原菌的鉴定符合率较高,且方法快速、简便,成本低廉,适合在临床微生物实验室中推广应用。

Objective To evaluate the direct identification of microorganisms from blood culture by a separation gel tube-based matrix-assisted laser desorption / ionization-time of flight mass spectrometry（ MALDI-TOF MS） and its identification rate. Methods 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. Results 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 Grampositive 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%. Conclusions 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.