Isolation And Identification,drug Sensitivity And Virulence Factors Detection Of Foodborne Listeria Monocytogenes

Listeria monocytogenes(LM)infect host mainly through contaminated food.The clinical symptoms show mainly gastroenteritis,meningitis,encephalitis,abortion,etc.,the fatality rate is as high as 20%-30%.LM is one of the four important food-borne pathogen,it can be detected in cooked food,aquatic products,frozen food,so,it has been paid more and more attention by food safety department.In order to understand the status of food contamination of Listeria monocytogenes in Xinjiang Production and Construction Corps,drug sensitivity,pathogenicity and the distribution of important virulence factors of food-borne LM isolates,bacteria were isolated and identified using GB method from 10 kinds of food for a total of 727 food,including lunch boxes,school meals,frozen surimi products,processed meat products,fresh meat,frozen drinks,salad,chicken,cheese,cakes collected in 2014 from 8 divisions of Xinjiang production and Construction Corps.Fourteen virulence factor genes of iap LIPI-1 and LIPI-2 and 37 LPXTG protein genes were detected by PCR,and some sequences were analyzed.17 drug susceptibility tests were carried out by disc diffusion method,and the pathogenicity of the isolates was preliminarily tested in mice.Results: 24 strains of bacteria were isolated from 727 food samples and identified as Listeria monocytogenes by Gram stain,culture characteristics and biochemical characteristics.The total detection rate of food LM was 3.3%,of which the highest detection rate of processed meat products,17.77%,followed by frozen surimi products,the detection rate of 4.95%.The detection rate of virulence-related iap gene was 95.8%.The detection rate of hLy,prfA,plcA,plcB,mpl were 100%and 54.1% of actA in LIPI-1.The detection rates of inlA,inlB and inlC genes were 100%,54.1%,50% and 37.5% of inlE,inlF and inlG,respectively in LIPI-2.In LPXTG protein genes,the detection rates of inlJ,lmo1413,inlH,lmo0331,lmo0610,lmo1799 and lmo2085 were 100%,of lmo0835,lmo2178,lmo2130,lmo0160,lmo0175,lmo0175,lmo0159,lmo0550,lmo0880,lmo1290,lmo1666 and lmo2714 were over 90%,of lmo0435,lmo0801,lmo2026 were below 15%,Lmo1115 was not detected.There are two copies of food there are virulence factors of different strains of mixed contamination of the situation.The distribution of the virulence factor gene showed that there were 2 strains with different virulence factors mixed contamination in the same food sample.The sequence analysis of inlC,E,F,G and iap from LM5567,LM5567 and LM5573 isolates showed that LM5567 and LM5573 belonged to lineage I and LM5570 belonged to lineage II.The homology between InlC,inlE,inlF,iap and Genbank 12 different serotypes of LM were 97%,87%,76% and 79%,between inlG and 5 different serotypes LM were above 91%.The inlF was conserved in the same lineage,and vary between different lineage.The drug sensitivity test showed that 24 strains of Listeria monocytogenes were resistant to penicillin and ciprofloxacin,most of them were sensitive to imipenem,doxycycline,vancomycin and gentamicin.Some strains showed multiple drug resistance,of which 6 strains were resistant to 3 drugs,accounting for 25% of the total isolates;4 strains were resistant to 4 drugs,4 strains were resistant to more than 5 drugs,ccounting for 16.6% of the total isolates.Animal pathogenicity experiment showed that different LM isolates were significantly different pathogenicity in mice.LM5567,LM5570,LM2941,LM2947,LM3197,LM6072 and LM461 could killed mice within 6 days,and LM6008,LM502,LM502-2 and LM472 could not kill mice.Conclusion: Food were contaminated by LM to different degrees,mixed contamination of different strains were existed;LIPI-2 virulence factor gene deletion was higher than LIPI-1 virulence factor gene deletion;Food-borne LM isolates were resistant to susceptible drugs,suggesting that food safety can not be ignored.