Canadian Grain Commission, Government of Canada, Winnipeg, Canada.
Public Health Agency of Canada, National Microbiology Laboratory, Government of Canada, Winnipeg, Canada.
PLoS One. 2021 Nov 4;16(11):e0259209. doi: 10.1371/journal.pone.0259209. eCollection 2021.
Microorganisms that cause foodborne illnesses challenge the food industry; however, environmental studies of these microorganisms on raw grain, prior to food processing, are uncommon. Bacillus cereus sensu lato is a diverse group of bacteria that is common in our everyday environment and occupy a wide array of niches. While some of these bacteria are beneficial to agriculture due to their entomopathogenic properties, others can cause foodborne illness; therefore, characterization of these bacteria is important from both agricultural and food safety standpoints. We performed a survey of wheat and flax grain samples in 2018 (n = 508) and 2017 (n = 636) and discovered that B. cereus was present in the majority of grain samples, as 56.3% and 85.2%, in two years respectively. Whole genome sequencing and comparative genomics of 109 presumptive B. cereus isolates indicates that most of the isolates were closely related and formed two genetically distinct groups. Comparisons to the available genomes of reference strains suggested that the members of these two groups are not closely related to strains previously reported to cause foodborne illness. From the same data set, another, genetically more diverse group of B. cereus was inferred, which had varying levels of similarity to previously reported strains that caused disease. Genomic analysis and PCR amplification of genes linked to toxin production indicated that most of the isolates carry the genes nheA and hbID, while other toxin genes and gene clusters, such as ces, were infrequent. This report of B. cereus on grain from Canada is the first of its kind and demonstrates the value of surveillance of bacteria naturally associated with raw agricultural commodities such as cereal grain and oilseeds.
引起食源性疾病的微生物对食品工业构成挑战；然而，在食品加工之前，对这些微生物在原始谷物上的环境研究并不常见。解淀粉芽孢杆菌是一组多样化的细菌，它们在我们的日常环境中很常见，并占据了广泛的生态位。虽然由于其昆虫病原特性，这些细菌中的一些对农业有益，但其他细菌会导致食源性疾病；因此，从农业和食品安全的角度来看，对这些细菌进行特征描述很重要。我们对 2018 年（n = 508）和 2017 年（n = 636）的小麦和亚麻谷物样本进行了调查，发现芽孢杆菌存在于大多数谷物样本中，分别为 56.3%和 85.2%。对 109 株假定的解淀粉芽孢杆菌分离株进行全基因组测序和比较基因组学分析表明，大多数分离株密切相关，并形成了两个具有遗传差异的群体。与现有参考菌株基因组的比较表明，这两个群体的成员与以前报道的引起食源性疾病的菌株没有密切关系。从同一数据集推断出另一个遗传上更为多样化的解淀粉芽孢杆菌群体，该群体与以前报道的引起疾病的菌株具有不同程度的相似性。与毒素产生相关基因的基因组分析和 PCR 扩增表明，大多数分离株携带 nheA 和 hbID 基因，而其他毒素基因和基因簇，如 ces，则很少见。本报告首次报道了加拿大谷物上的芽孢杆菌，证明了对与谷物和油籽等原始农产品自然相关的细菌进行监测的价值。
