MALDI-TOF-MS在儿童血流及尿路感染病原菌直接鉴定中的应用

Application of MALDI-TOF-MS in the direct identification of pathogenic bacteria from bloodstream and urinary tract infection children

目的探讨基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)在快速准确鉴定儿童血流及尿路感染病原菌方面的临床应用优势及操作关键点。方法收集西安市儿童医院血培养报警阳性瓶382份,尿常规提示感染的尿培养标本314份。血培养阳性标本经过MALDI Sepsitype试剂盒处理后采用MALDI-TOF-MS直接鉴定,尿液标本行差速离心富集细菌后直接采用MALDI-TOF-MS鉴定病原菌。直接鉴定结果与标本接种后传统培养12-48 h后的菌落鉴定结果进行比较。结果血培养阳性标本中18份标本为两种及两种以上菌混合感染,364份标本为单一菌感染,革兰阳性菌两种鉴定方法符合率为84.3%(177/210),革兰阴性菌鉴定符合率为88.4%(114/129),真菌鉴定符合率为44.4%(4/9)。在鉴定结果一致情况下,质谱直接鉴定较菌落鉴定指纹图谱干扰杂峰多,评分稍低;尿液培养菌落计数>105cfu/ml标本共265份,细菌直接鉴定符合率83.3%(221/265),儿童常见尿路感染细菌菌液倍比稀释后发现可靠的直接鉴定结果最低检测限分别为大肠埃希菌(104 cfu/ml)、肺炎克雷伯菌(105 cfu/ml)、肠球菌(106 cfu/ml)。结论MALDI-TOF-MS直接鉴定血培养报阳及尿液标本病原菌时,单一菌及高浓度菌感染鉴定快速且符合率高,可有效缩短检测时间,及时为临床危重患儿提供诊治依据。

Objective To explore the clinical advantages and key points of MALDI-TOF-MS and establish a accurate method for the identification of bloodstream and urinary tract infection pathogens in children.Methods A total of 382 positive blood culture samples and 314 urine culture specimens of urinary tract infection were collected from Xi’an Children’s Hospital.Blood culture positive specimens were treated with MALDI Sepsitype kit and then identified by MALDI-TOF-MS directly.Urine specimens were subjected to diffe-rential centrifugation for bacterial enrichment and then identified by MALDI-TOF-MS directly.The results of direct identification were compared with those of traditional identification culture 12-48 h after inoculation.Results Among the positive samples of blood culture,18 samples were infected with two or more bacteria,and 364 samples were infected with single bacteria.The results showed that the coincidence rate of two identification methods was 84.3%(177/210)for gram-positive bacteria,88.4%(114/129)for gram-negative bacteria and 44.4%(4/9)for fungi.Compared to the results of traditional identification,more interferential peaks appeared in fingerprints of direct identification with lower scores.There were 265 urine culture specimens,and the results showed that the coincidence rate of two identification methods was 83.3%(221/265).The minimum detection concentrations for Escherichia coli,Klebsiella pneumoniae and Enterococcus that can be directly identified were 104cfu/ml,105cfu/ml,106cfu/ml,respectively.Conclusion Direct identification of MALDI-TOF-MS has a high coincidence rate of single bacteria and high concentration bacteria infection,which can effectively shorten the detection time and provide timely diagnosis and treatment basis for clinically critical children.