Abstract: Objective To analyze the contamination of pathogenic bacteria and the characteristics of bacterial community in some retail packaged refrigerated ready-to-eat foods in Beijing. Methods In July 2022,65 retail packaged refrigerated ready-to-eat foods were collected in Beijing. Using national standard methods for food microbiological testing,Staphylococcus aureus,Escherichia coli,and Bacillus cereus were counted,and Salmonella,Listeria monocytogenes and diarrheagenic Escherichia coli were isolated and cultured. The macrogenomic sequencing was used to annotate the bacterial communities in food. Results Two samples had Escherichia coli counts >10 CFU/g,seven samples had Bacillus cereus counts >10³ CFU/g,and all samples had Staphylococcus aureus counts <10 CFU/g. Listeria monocytogenes was isolated from five samples,while Salmonella and diarrheagenic Escherichia coli were not isolated. Using metagenomic sequencing to annotate 124 phyla,621 families,2 315 genera,and 11 631 species,it was found that the relative abundance of Escherichia coli,Staphylococcus aureus,Listeria monocytogenes,and Bacillus cereus in two types of packaged refrigerated ready-to-eat foods ranked 3rd,23th,7th,121th,and 8th,5th,13th,287th on the species level,respectively. Conclusion The retail packaged refrigerated ready-to-eat foods in Beijing have pathogenic bacterial contamination,and Listeria monocytogenes is a key focus for prevention and control. The traditional cultivation methods may underestimate the contamination status of pathogenic bacteria,and combined with metagenomic sequencing technology,microbial contamination can be more comprehensively evaluated.

Key words: Prepackaged refrigerated ready-to-eat food, Pathogen contamination, Metagenomic sequencing