Distribution And Pathogenicity To LIPI-1 Genes Of Listeria Monocytogenes Among Food Samples

Listeria monocytogenes is a kind of important zoonotic disease pathogens, which can cause persons, various livestocks and fowls serious diseases. It can be detected from Raw meat, cooked meat, quick- frozen food, aquatic product and vegetable, multiply in food with large temperature range (1℃-45℃) including the cold temperature. Therefore, the longer food storage in the cold temperature with Lm, the greater their risk. So, it has been paid much more attention of the people and must be detected in the import and export food by China and many other countries.Since 1990s, many experts and scholars at home and abroad have studied the biological characteristics, detection technology, pathogenicity gene, virulence factors and epidemiological of Listeria monocytogenes.This paper used the current isolates of our laboratory, analyzed distribution and ragularity to LIPI-1 Genes of Lm among food samples, studied genotype and its distribution and compared virulence of Lm with different single gene and genotypes.The prfA gene was detected from all 105 Listeria monocytogenes strains isolated from six sources (raw meat, cooked meat, quick- frozen food, aquatic product and vegetable et al). The detectable rate of plcB and hly is 98.1% and 96.2%. That of mpl is 82.9%. The lowest detectable rate is 62.9% of plcA and 67.6% of actA.Identified LIPI-1 gene of 105 strains which had been isolated, 59 were identified as typeⅠ; 40 were identified as typeⅡ; 6 were identified as typeⅢ; The relationship between the distribution of LIPI-1 and sources of isolates was analyzed. TypeⅠisolates can be finded from all sorts of foods except vegetables and occupy most isolates from aquatic product. Every sort of food has been found carrying typeⅡisolates. The proportion of the isolates from quick- frozen food and aquatic product is lower than the average rate. The rate of typeⅢisolates is 5.8%.Pathogenicity test showed that all of them, plcA, actA and plcB, had reflected pathogenicity obviously. When the isolates losing plcA and actA simultaneously, the influence to pathogenicity of losing plcB is weaker than others. The performance of pathogenicity to mices with every gene deletion isolate was totally different. Overall, the more pathogenic genes be carried, the stronger the pathogenicity was. With the reduction of pathogenic genes carried by isolates, the pathogenicity reduced. All LIPI-1 genotypes had pathogenicity to mice. The entire discipline, the pathogenicity of typeⅠisolates was the strongest one and that of typeⅡisolates was stronger than that of typeⅢisolates, is clear. The tendency, the more pathogenic genes be carried, the stronger the pathogenicity was, also can be finded.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.