Bacterial communities in prepared foods available at supermarkets in Beijing, China

Prepared foods have received increasing attention owing to their convenience, rapidness, and ease of processing in a fast-paced life. The bacterial diversity and composition vary among different prepared foods and are closely related to food safety and human health. However, the knowledge on the bacterial community in prepared foods is still limited. In this study, the bacterial diversity in three kinds of prepared foods (meat, aquatic, and dish) available at supermarkets in Beijing was examined by using the high throughput sequencing technology to identify bacterial 16S rRNA genes. Alpha diversity analysis indicated that Proteobacteria and Firmicutes were the predominant bacterial phyla in prepared meat products, which accounted for 35-49% and 42-58% of the total sequences, respectively. Similar results were observed in prepared aquatic products, except salmon, which had a relatively unique bacterial community with Proteobacteria accounting for 90.72%. In prepared dishes, the proportions of Proteobacteria and Firmicutes were about 39-74% and 8-37%, respectively. The predominant bacterial genera detected in all samples within each kind of prepared foods were used to examine the differences in the bacterial community among three kinds of prepared foods. Results showed that the bacterial community in prepared meat products was much more diverse (14 genera) than those in prepared aquatic products (6 genera) and prepared dishes (2 genera). Acinetobacter was detected in all 288 prepared products. The bacterial community structures of prepared meat and aquatic products were more similar compared to those of prepared dishes. On the other hand, in prepared meat products, the bacterial communities of the samples with the same materials or brands were more similar, and further, among the sample with the same brands, the bacterial communities of the samples from the development zone were clearly different from those of the samples from the main urban area. In prepared aquatic products, the bacterial communities of the samples from the same region were also more similar. In prepared dish products, the bacterial communities of the samples with the same foodstuff or cooking style were more similar. In conclusion, this study revealed that the origin and type of prepared food ingredients, along with the sales location and processing methods, influenced microbial diversity and composition.