Analysis of microbiota in beef stored at different temperature over time.

Beef is one of the most popular meat worldwide, and outbreaks in fast-food chains have been frequently occurred by beef meat due to the contamination of foodborne pathogens before consumption. The contamination of pathogens in beef meat can influence on the spoilage of meat as well as foodborne illness. Thus, the influence of pathogen contamination on beef meat should be analyzed by microbiome for food safety. Here, we analyzed the influence of pathogen contamination on the shift of microbiota and interactions between microbes under different storage conditions. A total of 60 beef samples were stored at 25℃ and 4℃ until 24 hr, and the shifts of microbiota were analyzed using MiSeq system. The influence of pathogen contamination on microbiota was analyzed by artificially contaminated experiments with Escherichia coli FORC_044, which is isolated Enterohemorrhagic E. coli (EHEC) strain from the stool of a food-poisoned patient in Korea. The bacterial amounts and the proportion of Escherichia were increased more under 25℃ storage condition. Contaminated Escherichia was positively correlated with indigenous microbes such as Pseudomonas, Brochothrix, Staphylococcus, Rahnella, and Rhizobium in co-occurrence network analysis. Carnobacterium, which is one of potential spoilage microbe, was negatively correlated with other microbes including Escherichia. The predicted functions of altered microbiota showed that the pathways related to the process of spoilage including biosynthesis of acetic acid and lactic acid were increased over time. The shift of pathways was higher in contaminated beef meat stored at 25℃ than non-contaminated samples and 4℃ storage conditions. Carnobacterium, Lactobacillus and Escherichia were the main genera contributing to the shift of functional genes involved in the pathway. Results in this study indicated that the contamination of pathogen can influence on the spoilage of beef meat. This study can extend our understanding of beef microbiota, and it will be applied to manage beef products.