婴幼儿食品和配方奶粉中克罗诺杆菌污染调查及分子分型研究

目的了解温州市市售婴幼儿食品和配方奶粉中克罗诺杆菌污染情况及分子分型特征,分析不同菌株间亲缘相关性。方法参照GB 4789.40—2010《食品安全国家标准食品微生物学检验阪崎肠杆菌检验》方法在食品中分离鉴定克罗诺杆菌。采用脉冲场凝胶电泳(PFGE)和多位点序列分型(MLST)方法对克罗诺杆菌进行分型研究。结果 2013—2017年共采集737份婴幼儿食品和配方奶粉,克罗诺杆菌总检出率为6.1%(45/737)。其中婴幼儿谷类辅助食品检出率最高(23.4%,37/158)。45株克罗诺杆菌属于阪崎克罗诺杆菌(C.sakazakii)、丙二酸盐克罗诺杆菌(C.malonaticus)和莫金斯克罗诺杆菌(C.muytjensii)。其中阪崎克罗诺杆菌最多(73.3%,33/45),其次为丙二酸盐克罗诺杆菌(24.4%,11/45)。MLST共分为25个ST型,其中ST64、ST1、ST40、ST4和ST7为优势型别。45株克罗诺杆菌PFGE分型得到38个带型,未发现有明显的优势分型和聚集现象。PFGE型和MLST型结果分析表明,绝大数具有相同PFGE型的菌株也有相同的MLST型,而相同MLST型却不一定具有较高的亲缘关系。结论温州市市售婴幼儿食品和配方奶粉中克罗诺杆菌的污染状况较轻,其中婴幼儿谷类辅助食品检出率最高。食品来源的克罗诺杆菌图谱具有高多态性和离散性。

Contamination status and molecular typing of Cronobacter in infant food and formula powder

Objective To investigate the contamination and molecular typing characteristics of Cronobacter in infant food and formula powder in Wenzhou, to analyze the genetic relationship between different strains. Methods According to the national standard GB 4789.40-2010, Cronobacter was isolated and identified from food. Pulse field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to analysis the genotyping of Cronobacter. Results A total of 737 food samples were collected from 2013 to 2017, and the total detection rate of Cronobacter was 6.1% (45/737). The detection rate of infant formula rice flour was the highest, 23.4% (37/158). Totally 45 strains of Cronobacter were identified as C.sakazakii, C.malonaticus and C.muytjensii. Among them, C.sakazakii was the majority, accounting for 73.3%(33/45), followed by C.malonaticus of 24.4%(11/45). There were 25 ST types in 45 strains, and ST64, ST1, ST40, ST4 and ST7 were the dominant types. 45 strains of Cronobacter were divided into 38 clusters, and no obvious dominant cluster and aggregation were found. The result of PFGE and MLST showed that the majority of strains with the same PFGE type also had the same MLST type, but the same MLST type did not necessarily indicate a high genetic relationship. Conclusion The contamination level of Cronobacter was relatively low in foods of Wenzhou, among which the detection rate of infant formula rice flour was the highest. Cronobacter isolated from foods showed highly polymorphism and dispersion.