即食食品中阪崎克罗诺杆菌的分离鉴定及分子分型

Isolation,Identification and Molecular Characterization of Cronobacter sakazakii in Ready-to-eat Foods

为了解即食食品中污染阪崎克罗诺杆菌的流行情况,分析我国阪崎克罗诺杆菌主要流行菌株,对即食食品中分离的10株阪崎克罗诺杆菌进行基质辅助激光解析/电离飞行时间质谱(MALDI-TOF-MS)、VITEK 2、16s rDNA鉴定,采用多位点序列分型(MLST)方法对分离菌株进行分型,并对PubMLST数据库中322株中国分离株进行比对分析。结果表明:5740 m/z附近的蛋白峰为阪崎克罗诺杆菌的特征峰,5380m/z、6255m/z和7159m/z附近的蛋白峰形差异较大,可作为菌株分型的基础数据。163株分离细菌中有10株被鉴定为阪崎克罗诺杆菌,分为4个ST型(ST21、ST73、ST60、ST7),主要分离来源为谷类食品。我国阪崎克罗诺杆菌主要分离自临床样品、植物性食品、婴幼儿配方食品,主要的流行菌株为ST21型。本研究为分析食品中阪崎克罗诺杆菌可能的污染来源、流行规律及防控措施提供依据,有利于降低克罗诺杆菌在即食食品中的传播风险。

The aim of this study is to investigate the contamination of Cronobacter sakazakii in ready-to-eat foods,and to analysis the epidemic strains isolated in China.Ten strains were isolated from ready-to-eat foods,and the identification was performed by use of MALDI-TOF-MS,VITEK 2 and 16s rDNA sequence analysis.Multilocus sequence typing(MLST)method was employed for genotyping of the isolates.The phylogenetic tree was constructed by analyzing the sequences of the strains which were isolated in China in PubMLST database.MALDI-TOF-MS results revealed that the protein peak of 5740 m/z is the specific protein in C.sakazakii,and there are some differences in the proteins peaks of 5380 m/z,6255 m/z,7159 m/z which provide basic data for further genotyping by MALDI-TOF-MS.There were ten C.sakazakii strains identified from 163 isolates.MLST analysis results demonstrated that there were four sequence types(ST21,ST73,ST60,ST7)of the 10 isolates and the main resources of the isolates were cereal foods.The main resources of the isolates in China were clinical,plant food and infant formula.The ST21 strains were more epidemic than the others in China.This study provide basic data for source tracking,epidemiological investigating and control of C.sakazakii,it is useful in reducing the dissemination risk of C.sakazakii in ready-to-eat foods.