Characteristics Of Biofilm Formation Of RAW Meat-borne Listeria Monocytogenes In Meat Juice

Listeria monocytogenes is one of the most important foodborne pathogens,which can cause serious diseases in human.The commonly found foodborne pathogen can attach to various surfaces to form biofilm which leads to poor hygienic conditions in food processing environments and cross contamination of food products,and brings risks to public health.Recent research toward biofilm formation of foodborne pathogens are commonly based on standard strains and laboratory media,which can hardly represent the real condition in food system.Hence,meat juice can be used as an ideal culture medium for bacterial biofilm to simulate the growing condition in meat processing environment.Therefore,the research contents of this paper are as follows:1.47 L.monocytogenes isolates were separated and identified from 153 retailed raw meat samples in Shanghai area with the total contamination rate 13.72%,and 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,among which 1/2a-3a group was predominant.2.Calgary biofilm device was introduced to cultivate biofilm,and crystal violet staining and viable cell enumeration were used to determine the 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 in pork juice.3.When co-cultured in pork juice,the cell numbers of Salmonella enterica,Staphylococcus aureus and L.monocytogenes had a significant decrease or decreasing tendency compared to mono-species biofilm.Using confocal laser scanning microscope(CLSM),we found that the connection between the bacteria was looser and the thickness of multi-species biofilm was less than that of mono-species biofilm.In conclusion,the contamination rate in raw meat product is still alarming in Shanghai area;there were still possibility for the outbreak of listeriosis.Pork juice is the most suitable medium for L.monocytogenes to form biofilm,which revealed government should keep a close eye on product in processing and circulation environment of raw pork meat.A competitive interaction among the three species in multi-species biofilm was also revealed in this study.