Distribution And Pathogenicity To Virulence Genes Of Foodborne Listeria Monocytogenes

Listeria monocytogenes is a kind of important foodborne diseases pathogens, which can cause serious diseases in adults and infants, and the death rate may be as high as 30%. It has strong tolerance to the environment and can multiply in food with large temperature range (0℃-45℃). In recent years, with the growing of refrigerated and frozen food, the risk are getting more and more serious. Since 1990s, many experts and scholars at home and abroad have studied the biological characteristics, detection technology, virulence factors and epidemiological of Listeria monocytogenes.This paper used the current isolates of our laboratory, analyzed distribution and ragularity to virR and other genes which are regulated by it of Listeria monocytogenes among food samples, studied genotype and its distribution and compared virulence with different single gene and genotypes.171 Listeria monocytogenes strains isolated from raw meat, aquatic product, vegetable, cooked meat and quick- frozen food were detected. Results showed that, the detectable rate of virR、mprF、dltA、dltB、dltC、dltD were 95.3%、98.8%、93.0%、95.9%、100% and 89.5% respectively. Such findings suggest that the distribution of different genes in Listeria monocytogenes from different sources were different. Identified genes of 171 strains which had been isolated, 138 were identified as typeⅠ; 24 were identified as typeⅡ; 1 were identified as typeⅢand 8 were identified as typeⅣ. The relationship between the distribution of different genotypes and sources of isolates was analyzed. The rate of typeⅠisolates is 80.7%. It can be finded from all sorts of foods especially in cooked meat. The rate of typeⅡisolates is 14% and it can be finded from the other four sources of isolates. The proportion of the isolates from vegetable is higher than the average rate. Only one sort of food has been found carrying typeⅢisolates. The rate of typeⅣisolates is 4.7%.Pathogenicity test showed that all of them, virR, dltA and dltD, had different performance of pathogenicity to mices. There is no doubt that virR has the strongest pathogenicity. Overall, the more pathogenic genes be carried, the stronger the pathogenicity was. With the reduction of pathogenic genes carried by isolates, the influence degree of pathogenicity is also more and more little. Representative strains of all genotypes had pathogenicity to mice. Among typeⅠ、typeⅡand typeⅣ, the entire discipline, the pathogenicity of typeⅠisolates was the strongest one and that of typeⅡisolates was stronger than that of typeⅣisolates, is clear.It is needed that the pollution conditions of Listeria monocytogenes in foods as well as epidemiologic conditions of this pathogen are further investigated for the supervision of Listeria monocytogenes, the examination of explosion and spread as well as tracking to pollrter to providing basis.