可能的污染路线,环境适应,和克隆杆菌属的遗传基础。在2012年至2018年为期7年的全国连续监测中,通过实验室研究和全基因组比较分析确定了中国大陆的婴儿和后续配方奶粉生产工厂和零售产品.对生产过程的2年连续多中心监测(2013年和2014年进行)揭示了Cronobacterspp的来源。在干混过程中,原干成分和制造环境(特别是在振动筛和真空吸尘器中),而在组合过程中,主要污染源被确定为包装室。重要的是要注意,根据从生产过程监控中获得的污染控制知识,从2016年起,中国零售婴幼儿配方奶粉(PIF)和后续配方奶粉(FUF)产品的污染率显著下降,在改进工厂卫生管理实践后。克罗恩杆菌属的流行。2018年中国零售PIF和FUF从1.55%(2012年61/3925)大幅下降至平均低至0.17%(2018年13/7655)。对总共90个Cronobacter种进行了表型确定和基因组分析。从监测中获得的分离株。在90个分离物中,只有两个对头孢唑啉或头孢西丁表现出抗性。多位点序列分型结果显示,Sakazakii序列1型(ST1),ST37和C.malonaticusST7是从生产工厂收集的显性序列类型(STs),而在全国零售的PIF和FUF中检测到的主要STs是SakazakiiST1,ST4,ST64和ST8。1株SakazakiiST4分离物(1.1%,1/90)具有很强的生物膜形成能力,有13个分离株(14.4%,13/90)的生物膜形成能力较弱。基因组分析显示Cronobacterspp。具有相对稳定的核心基因组和不断增加的泛基因组大小。质粒IncFIB(pCTU3)在该属中很普遍,其中一些包含14种抗菌杀菌剂和金属抗性基因(BMRG),包括铜,银,和抗砷基因。质粒IncN_1预计含有6个ARGs。这是首次在克罗恩杆菌属中报道多重耐药的IncN_1型质粒。关于BMRG的基因组变异,毒力基因,抗菌素抗性基因(ARGs),在该属的菌株中观察到与生物膜形成有关的基因。生物膜形成组和非生物膜形成组之间bcsG和flgJ的拷贝有明显差异,这两个基因在生物膜形成中起着关键作用。这项研究的发现增进了我们对Cronobacterspp的污染特征和遗传基础的理解。PIF和FUF及其在中国的生产环境,并为减少PIF和FUF生产过程中对该病原体的污染提供重要指导。
The possible contamination routes, environmental adaptation, and genetic basis of Cronobacter spp. in infant and follow-up formula production factories and retailed products in mainland China have been determined by laboratory studies and whole-genome comparative analysis in a 7-year nationwide continuous surveillance spanning from 2012 to 2018. The 2-year continuous multicenter surveillance of the production process (conducted in 2013 and 2014) revealed that the source of Cronobacter spp. in the dry-blending process was the raw dry ingredients and manufacturing environment (particularly in the vibro sieve and vacuum cleaner), while in the combined process, the main contamination source was identified as the packing room. It is important to note that, according to the contamination control knowledge obtained from the production process surveillance, the contamination rate of retail powdered infant formula (PIF) and follow-up formula (FUF) products in China decreased significantly from 2016 onward, after improving the hygiene management practices in factories. The prevalence of Cronobacter spp. in retailed PIF and FUF in China in 2018 was dramatically reduced from 1.55 % (61/3925, in 2012) to an average as low as 0.17 % (13/7655 in 2018). Phenotype determination and genomic analysis were performed on a total of 90 Cronobacter spp. isolates obtained from the surveillance. Of the 90 isolates, only two showed resistance to either cefazolin or cefoxitin. The multilocus sequence typing results revealed that C. sakazakii sequence type 1 (ST1), ST37, and C. malonaticus ST7 were the dominant sequence types (STs) collected from the production factories, while C. sakazakii ST1, ST4, ST64, and ST8 were the main STs detected in the retailed PIF and FUF nationwide. One C. sakazakii ST4 isolate (1.1 %, 1/90) had strong
biofilm-forming ability and 13 isolates (14.4 %, 13/90) had weak
biofilm-forming ability. Genomic analysis revealed that Cronobacter spp. have a relatively stable core-genome and an increasing pan-genome size. Plasmid IncFIB (pCTU3) was prevalent in this genus and some contained 14 antibacterial biocide- and metal-resistance genes (BMRGs) including copper, silver, and arsenic resistant genes. Plasmid IncN_1 was predicted to contain 6 ARGs. This is the first time that a multi-drug resistance IncN_1 type plasmid has been reported in Cronobacter spp. Genomic variations with respect to BMRGs, virulence genes, antimicrobial resistance genes (ARGs), and genes involved in
biofilm formation were observed among strains of this genus. There were apparent differences in copies of bcsG and flgJ between the
biofilm-forming group and non-
biofilm-forming group, indicating that these two genes play key roles in
biofilm formation. The findings of this study have improved our understanding of the contamination characteristics and genetic basis of Cronobacter spp. in PIF and FUF and their production environment in China and provide important guidance to reduce contamination with this pathogen during the production of PIF and FUF.