Bacterial microbiota associated with raw plant-based meat analogue products and their influences on selective enrichment for Escherichia coli O157:H7

Towards fostering a more sustainable food production system in face of the climate change challenge, alternative protein meat-substitute products that are plant-based and free of animal by-products have been gaining attractions from both food manufacturers and consumers. With these so-called plant-based meat analogues (PBMAs) becoming increasingly available at supermarkets, there is very little known about their microbial properties. In this short report, we characterized the bacterial composition of raw plant-based ground meat imitation retail products using 16S rRNA gene amplicon sequencing. Despite the observed bacterial community dissimilarity between sample brands, a total of 18 shared genera (dominated by Bacilli and Gammaproteobacteria classes) were identified as the core constituents of the bacterial microbiota of these PBMA products. Within the scope of food safety testing, to gain insights on the dynamics of the enrichment process for <i>E. coli</i> O157:H7 in accordance with the Health Canada reference method MFHPB-10, bacterial taxonomic analyses were conducted at different stages of the prescribed cultural procedures. Using both control and <i>E. coli</i> O157:H7-inoculated PBMA samples it was revealed that, independent of the presence of <i>E. coli</i> O157:H7, off-target bacteria of the <i>Clostridium sensu stricto 1</i> genus were significantly enriched from the uncultured samples. Additionally, the abundance of <i>Hafnia-Obesumbacterium</i> bacteria in the PBMA samples was also increased in the enrichment products, but only when <i>E. coli</i> O157:H7 was absent. Consistent with the spread-plating results indicating that the inoculated <i>E. coli</i> O157:H7 cells were capable of reaching a high density (>10⁸ CFU/ml) in the resultant enrichment cultures, the significant enrichment of bacterial 16S rRNA gene sequences belonging to the targeted genus of <i>Escherichia,</i> but not <i>Hafnia-Obesumbacterium</i>. This further highlights the competitive nature of the selective enrichment for <i>E. coli</i> O157:H7 against specific background bacteria associated with the PBMA products.