MALDI-TOF MS用于沙门菌食源性疾病暴发同源性分析初步研究

Preliminary study on homology analysis of Salmonella isolatedfrom foodborne disease outbreaks by MALDI-TOF MS

目的评价基质辅助激光解吸电离飞行时间质谱(matrix-assisted laser desorption/ionization time-of-flight mass spectrometry,MALDI-TOF MS)技术用于沙门菌食源性疾病暴发同源性分析的效果,为沙门菌暴发疫情处置提供技术支持。方法收集长沙市近年5起食源性疾病暴发事件相关的42株沙门菌,进行生化鉴定和血清学分型并对其进行脉冲场凝胶电泳(pulsed-field gel electrophoresis,PFGE)分型分析。应用MALDI-TOF MS技术采集42株沙门菌质谱数据构建主要谱图后进行质谱鉴定,并对42株沙门菌进行相关距离聚类同源分析,再对不同事件的相关沙门菌分4次分别进行不加参考菌株和加入参考菌株的聚类同源分析,并与PFGE聚类分析结果进行比较。结果29份食品中分离出5株沙门菌,62份病人标本中分离出37株沙门菌,42株沙门菌的质谱鉴定结果和生化鉴定结果符合率为100%,血清学鉴定分为3个血清型,肠炎沙门菌22株,布伦登卢普沙门菌17株,鼠伤寒沙门菌3株。PFGE将5次事件的沙门菌分成了4个内部完全一致的分支,42株沙门菌的质谱聚类在300的相对相关距离水平上分为3个不同的分支,和血清学分型一致,和PFGE聚类分型大致相同。4次无参考菌株的质谱分别聚类同源分析不能将相关菌株聚类为预期的簇,但加入参考菌株后的质谱聚类同源分析能将同一事件中的菌株聚类成相似度接近100%的一簇,和PFGE分型结果高度一致。结论MALDI-TOF MS聚类分析可在一定范围内应用于沙门菌食源性疾病暴发同源性的病原学确认,可作为PFGE同源性分析的一种较好补充方法,但其不能直接将不同平台数据进行比较。

Objective To evaluate the feasibility of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF MS)for homology analysis of Salmonella isolated from foodborne disease outbreaks,and to provide technical support for the treatment of Salmonella outbreaks.Methods We collected 42 strains of Salmonella associated with 5 foodborne disease outbreaks in Changsha City in recent years,and then performed biochemical identification,serotyping and PFGE typing.The mass spectrum data about the 42 Salmonella strains were collected by MALDI-TOF MS technology to construct the main spectrum(MSP),and then the MSP was identified by MBT Compass software.Correlation distance cluster homology analysis was performed on the 42 Salmonella strains,and then 4 times of cluster homology analyses without and with reference strains were conducted on the related Salmonella strains of different events.The results of MSP dendrogram were compared with those of PFGE cluster analysis.Results Five Salmonella strains were isolated from 29 food samples,and 37 Salmonella strains from 62 patient samples.The results of MSP and biochemical identification of the 42 Salmonella strains were completely consistent,and the strains were identified as 22 strains of Salmonella enteritidis,17 strains of Salmonella braenderup and 3 strains of Salmonella typhimurium.The Salmonella strains from the 5 events were divided into four internal completely consistent branches by PFGE.MSP dendrogram of the 42 Salmonella strains was divided into three different branches at the level of 300 relative correlation distance,which was consistent with serotyping and roughly the same as PFGE cluster typing.Four times of mass spectrometry clustering homology analysis without reference strains could not cluster related strains from the expected cluster,but after adding reference strains,the strains in the same event were clustered into a cluster with close to 100%similarity,which was highly consistent with the PFGE typing results.Conclusion MALDI-TOF MS clustering analysis by MSP dendrogram can be used to confirm the homology of Salmonella foodborne disease outbreaks in a certain range,and can be used as a good complementary method to PFGE homology analysis,but it cannot directly compare different platform data.