婴幼儿配方乳粉及婴幼儿米粉中的蜡样芽胞杆菌流行情况、耐药性及分子特征研究

Study on the occurrence, antimicrobial resistance profiles and genomic feature of Bacillus cereus in infant formula milk powder and rice cereal

中文关键词:  蜡样芽胞杆菌  全基因组测序  抗生素抗性  多重耐药  毒力因子

英文关键词:Bacillus cereus  whole-genome sequencing  antibiotic resistance  multi-drug resistant  virulence factor

中文摘要:

      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 GB 4789.14—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。

英文摘要:

      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 11 typical 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.