【摘要】 目的 了解流通环节市售婴幼儿配方乳粉和婴幼儿米粉中的蜡样芽胞杆菌流行情况、抗生素耐药性和毒力基因等分子特征。方法 采用GB4789.14—2014《食品安全国家标准食品微生物学检验蜡样芽胞杆菌检验》对样品中的蜡样芽胞杆菌进行检测与生化鉴定。进一步通过抗生素敏感实验和全基因组测序对11株代表性分离株进行研究,获得耐药表型及耐药、毒力基因等分子特征信息。结果 婴幼儿配方乳粉和婴幼儿米粉中蜡样芽胞杆菌的检出率分别为11.97%(56/468)和20.74%(28/135)。11株代表性蜡样芽胞杆菌均为多重耐药菌株,全基因组测序结果发现11株分离株共携带8个耐药基因和14个毒力基因,其中主要携带磷霉素、β-内酰胺类抗生素抗性基因,以及肠毒素基因(hbl和nhe),另发现1株携带ces基因簇蜡样芽胞杆菌菌株。多位点序列分型表明,11株分离株具有遗传多样性,分属10个ST型。结论 婴幼儿配方乳粉和婴幼儿米粉中的蜡样芽胞杆菌检出率较低,但代表菌株的耐药谱和遗传特征具有多样性,应进一步加强监测及采取有效措施进行控制,以保障相关食品的安全性。更多还原

【Abstract】 Objective To comprehensively investigate the prevalence and the molecular characteristics of Bacillus cereus in commercially available infant formula milk powder and infant rice cereal, including antibiotic resistance and virulence. Methods The Bacillus cereus in the samples was detected and biochemical identified by GB 4789.14—2014 Food safety national standard-food microbiological test-Bacillus cereus test. Further research was conducted on 11 representative isolates through antibiotic sensitivity experiments and whole-genome sequencing to obtain molecular characteristic information such as resistance phenotype and resistance and virulence genes.Results The detection rates of Bacillus cereus in both infant formula milk powder and infant rice cereal were 11.97%(56/468) and 20.74%(28/135), respectively. Furthermore, multi-drug resistance was observed in the 11typical strains of Bacillus cereus identified in this study. The results of whole-genome sequencing revealed that these strains totally carried 8 antibiotic resistance genes and 14 virulence genes. Fosfomycin and β-lactam were identified as major resistance genes, while the enterotoxin gene of hbl and nhe were found to be the predominant virulence factors among the isolated strains; additionally, one strain carried the ces gene cluster as well. Multilocus sequence typing indicated genetic diversity among the 11 isolates which could be classified into 10 different ST types.Conclusion The detection rate of Bacillus cereus in infant formula powder and infant rice powder is low, but the resistance spectrum and genetic characteristics of the representative strains are diverse, so it is necessary to further strengthen monitoring and take effective measures to control, so as to ensure the safety of related food.更多还原