Community Structure Analysis Of Listeria Monocytogenes Biofilms In The Food Processing Environment

Listeria monocytogenes, as a common foodborne, was defined of one of four foodborne pathogens by World Health Organization, with a high mortality rate of 20%-40%. Under the background of paying more attention to global environmental health and food safety, the doses of disinfectant applied to medical and health care, animal husbandry and veterinary medicine, food, and daily use cosmetic are incrsing in their processing environment. Biofilm formation is one of the main reasons to produce resistance of microorganisms to disinfection, and the natural biofilms are communities of microorganisms that exhibited in the form of symbiotic codependence, Listeria monocytogenes is included. Listeria monocytogenes and commensal bacteria form biofilms together, which may help it survive under the local environments with disinfectants.In this study, we investigated Listeria monocytogenes-positive biofilms at food production facilities, and the dominant bacterial species of the biofilms were identified to determine the properties of the microbiological background. The main contents and results were as follows:1. The ISO 11290 method was used for the detection and isolation of Listeria monocytogenes, and the species were further identified based on 16S rDNA and hly genes. Out of 100 drain samples, eight were naturally contaminated with Listeria monocytogenes.2. To research the resistance of Listeria monocytogenes to disinfectant, the minimum inhibitory conentration (MIC) of Listeria monocytogenes for benzalkonium chloride were determined, and found that the MICs of BC for all eight isolated L. monocytogenes strains were between 18 and 35μg/ml. These findings indicate that L. monocytogenes exhibits resistance to chemical disinfection at food production facilities.3.16S rDNA gene-based cloning, terminal restriction fragment length polymorphism, and denaturing gradient gel electrophoresis were combined to evaluate the community structure for Listeria monocytogenes-positive biofilms in the drains of food processing facilities. Three molecular methods consistently showed that Pseudomonas psychrophila, Pseudomonas sp., and Klebsiella oxytoca were dominant species in 3Q,5Q, and 6Q samples; Aeromonas hydrophila and Klebsiella sp. were significantly dominant in 1-2,1-3, and 3-2 samples; Aeromonas hydrophila and Klebsiella oxytoca were dominant in the 2-3 sample; and Aeromonas hydrophila and Pseudomonas sp. were prominent in the 3-3 sample. Different biofilms from the same plant shared common bands, suggesting that similar bacteria can be found and can be dominant in different biofilms.This study provides a better understanding of the community structure for Listeria monocytogenes-positive biofilms in the drains of food processing facilities. It will provide a full analysis of biofilm formation mechanism for pathogeic microorganisms in the industrial processing environment, and establish a new theoretical basis for the further studies in predicting effective disinfection strategies to pathogeic microorganisms.