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目的分析广西市售婴儿食品中的克罗诺菌分离株的种类、表型和基因特性。方法将保存的试验菌株进行复苏,通过API 20E生化条和omp A基因扩增检测进行初步鉴定,扩增16S r RNA基因后进行测序,将获得的全16S r RNA基因序列在Gene Bank数据库上比对,构建进化树,确认是否为克罗诺菌。将试验菌接种于显色平板观察其表型和黄色素的产生情况,通过手工生化进行分型,确定其种属。结果 9株分离菌确定为克罗诺菌,有5种生化型,属于4个克罗诺种。检出Cronobacter sakazakii 6株菌,C.malonaticus、C.muytjensii和C.dublinensis各有1株;7株菌符合API 20E鉴定结果,9株分离菌均可检测到omp A基因。结论广西市售婴儿食品中克罗诺菌的污染以C.sakazakii为主,生化表型、种属及基因型具有多样性;鉴定时仅以单一的生化或其他表型作为判别依据存在很大的局限,需辅以分子生物学手段加以鉴别。
Objective To analyze the types, phenotypes and genetic characteristics of Cronacterium isolates in commercial baby food in Guangxi. Methods The preserved test strains were resuscitated and preliminary identification was performed by API 20E biochemical analysis and omp A gene amplification. After 16S rRNA gene was amplified and sequenced, the obtained 16S rRNA gene sequence was compared with Gene Bank database Yeah, build a phylogenetic tree to see if it is Cronobacter. The test bacteria were inoculated on a chromogenic plate to observe the phenotype and the production of the yellow pigment, and the type was determined by manual biochemistry. Results Nine isolates were identified as Cronobacterium, which had five biochemical types and belonged to four Cronnaceae species. Six strains of Cronobacter sakazakii were detected, one for C.malonaticus, C.muytjensii and C.dublinensis respectively. Seven strains were identified according to API 20E. Nine strains of omp A gene were detected. Conclusions The contamination of Cronorrhea bacteria in commercial baby food in Guangxi is mainly C.sakazakii with biochemical phenotypes, species and genotypes diversity. Only a single biochemical or other phenotype is identified as a basis for discrimination The limitations, to be supplemented by molecular biology methods to be identified.