MALDI-TOF MS直接鉴定阳性厌氧血培养瓶中细菌的研究

Study on the direct identification of bacteria in positive anaerobic blood culture flask by MALDI-TOF MS

目的探讨基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)直接鉴定阳性厌氧血培养瓶中细菌的可行性和准确性,评价不同前处理方法用于质谱快速鉴定的临床应用价值。方法收集2017年8月至2018年8月临床非重复阳性厌氧血培养瓶,经革兰染色镜检确认均有菌生长。利用分离胶促凝管法和0.5%十二烷基硫酸钠(SDS)法处理阳性厌氧血培养瓶并用MALDI-TOF MS直接鉴定,与转种后菌落鉴定结果相比较,分析鉴定准确率和一致性。结果共收集阳性厌氧血培养瓶240瓶,包括单菌阳性234瓶,混合菌6瓶,平均报阳时间为(16.87±13.12)h;218瓶(90.83%)可用MALDI-TOF MS直接鉴定,4瓶(1.67%)混合菌生长仅鉴定其中一种菌或无可靠鉴定结果。SDS法和分离胶法对革兰阴性菌的鉴定准确率(94.81%、94.16%)显著高于革兰阳性菌(87.50%、81.25%),差异有统计学意义(χ2=3.96、9.53,P<0.05);SDS法和分离胶法直接鉴定与菌落鉴定结果的一致率分别为92.31%、89.74%。SDS法前处理鉴定的准确率和鉴定分值≥2.0的比例(94.17%、69.23%)均高于分离胶法(90.83%、65.81%);SDS法厌氧菌的鉴定分值≥2.0的比例(83.33%)明显高于分离胶法(58.33%)。结论MALDI-TOF MS可应用于临床常见厌氧血培养阳性菌的鉴定,SDS法前处理对厌氧菌的快速鉴定有较高的准确率。

Objective To investigate the feasibility and accuracy of matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF MS)for direct identification of bacteria in positive anaerobic blood culture bottles,and to evaluate the clinical application value of different pretreatment methods for rapid identification of mass spectrometry.Methods Clinical non-repetitive positive anaerobic blood culture bottles were collected from August 2017 to August 2018,and the bacterial growth was confirmed by gram staining microscopy.Positive anaerobic blood culture bottles were treated by separating gel-accelerating tube method and 0.5%sodium dodecyl sulfate(SDS)method and identified directly by MALDI-TOF MS.The accuracy and consistency of identification were compared with the results of colony identification after transfection.Results A total of 240 bottles of positive anaerobic blood culture were collected,including 234 bottles of positive single bacteria and 6 bottles of mixed bacteria,with an average time of(16.87±13.12)h;218 bottles(90.83%)could be directly identified by MALDI-TOF MS,and 4 bottles(1.67%)could only identify one of them or no reliable identification results.The accuracy of SDS and gel isolation for the identification of gram-negative bacteria(94.81%,94.16%)was significantly higher than that of gram-positive bacteria(87.50%,81.25%,χ2=3.96,9.53,P<0.05),and the coincidence rates of SDS and gel isolation for direct identification and colony identification were 92.31%and 89.74%,respectively.The rate of accuracy and identification score≥2.0 of SDS pretreatment(94.17%,69.23%)was higher than that of gel separation(90.83%,65.81%);the rate of identification score≥2.0 of SDS anaerobic bacteria(83.33%)was significantly higher than that of gel separation(58.33%).Conclusion MALDI-TOF MS can be used to identify common anaerobic blood culture positive bacteria in clinic.SDS pretreatment has a high accuracy in rapid identification of anaerobic bacteria.