Pork juice promotes biofilm formation in Listeria monocytogenes

A total of 47 Listeria monocytogenes isolates were separated and identified from 153 retailed raw meat samples in Shanghai area with the highest contamination rate in pork meat (20.34%). Using multiplex PCR, these isolates were divided into 3 serogroups: 1/2a-3a, 1/2b-3b-7, and 1/2c-3c, and 1/2a-3a was predominant in these isolates. Calgary device was introduced to cultivate biofilm, and crystal violet staining and viable cell enumeration was used to determine the quantity of biofilm formation. Meat juices significantly impacted the biofilm formation, and L. monocytogenes had the highest biofilm-forming ability in pork juice. However, there was no significant difference on biofilm formation among different serotypes and sources. When cocultured in pork juice, the cell numbers of Salmonella enterica, Staphylococcus aureus, and L. monocytogenes had a significant decrease or decreasing tendency compared to monospecies biofilm, which revealed a competitive interaction among the three species. Practical applicationsIt is aimed to investigate the biofilm formation by L. monocytogenes on plastic surface in different meat juices (beef, chicken, and pork) and the interaction among the multispecies biofilm of Salmonella, Staphylococcus aureus, and L. monocytogenes in pork juice. Meat juice was used as a simulation of the real condition in meat processing environment, and the result can give suggestions to meat industry to keep a close eye on raw pork product.