| Foodborne pathogens are the most important factors that cause food safety events.The identification method for foodborne pathogens,especially rapid detectiong technology,is the key to promote the monitoring and control of foodborne pathogens.The bacterial resistance has become the most concern public issure in the world.In order to strengthen the risk assessment and control of antibiotic resistance,the antibiotic resistance mechanism and epidemic characteristics in vital foodborne pathogens are studied at home and abroad.Salmonella,as gram negative bacteria carried in livestock and poultry,is the most serious foodborne pathogen,which causes meat,eggs and milk pollution.Recently,people pay more attention to mobile colistin resistance gene(mcr-I)in gram-negative bacteria.However,there is no comprehensive report regarding the prevalence and transmission mechanism of mcr-1 in Salmonella China.Therefore,the study was aim to investigat the characteristic of antibiotic resistance in Salmonella from animal and human,then,study the prevalence and transmission mechanism of mcr-l.In addition,the study was in order to establish a high-throughput method for identification of foodborne pathogens and detection of resistance and virulence genes,simultaneously.The antibiotic characteristics were firstly investigated in 1312 animal origin Sallmonella isolates and 2034 human origin Sallmonella isolates from the year 2012 to 2015.Meanwhile,the prevalence of mcr-l was studied in these Sallmonella isolates.The results showed that their antibiotic characteristics are different.The reistance to Sulfamethoxazole,Tetracycline and Ampicillin was the most serious in animal original Sallmonella isolates,and the reistance to Ciprofloxacin,Cefotaxime and Gentamic was the most serious in huamn original Sallmonella isolates.The multi-drug reistance of Sallmonella isolates from animal was more serious than that from human.Generally,the prevalence of mcr-l was low,and the dominant serotype of Sallmonella carrying mcr-l was typhimurium.The rate of mcr-l was 1.98%(26)in 1312 animal origin Sallmonella isolates,and the mcr-1 positive Sallmonella were all from in pig orgin Sallmonella.While,the rate of mcr-I was 1.38%(28)in 2034 humanl origin Sallmonella isolates.The molecular epidemiological characteristics of 54 mcr-1 positive Salmonella were analyzed by three methods(MLST,PFGE and SNPs).Then,54 mcr-l positive Salmonella were analyzed by S1-PFGE and conjugation assay.Finally,the molecular geetic environment of mcr-l gene plasmid was investigated.The study results showed that ST34 was predominant molecular type in all mcr-1 positive Sallmonella.The result of PFGE and SNPs indicated that mcr-1 positive Sallmonella might spread clonally.mcr-l was located at different sizes of plasmid,which belonged to IncX4,IncI2 and IncHI2.The type of transfer of plasmid carrying mcr-l gene included the combination of successful and unsuccessful.The mcr-1 could be propagated directly through the conjugation,and tra gene might be the key gene for conjugation.The last part of the study was the establishment of a high-throughput method for identification of 22 foodborne pathogens and the detection of resistance and virulence genes,simultaneously.The specificity multi-PCR and random PCR is 95%and 94%,and their sencentivity is Ing/uL and 800ng/?L,respectly.The application can maximize the performance of microaary based the two PCR strategy.Multi-PCR microarray was with the better sensitivity and random PCR microarray was with the high-throughput perfomance.Generally,this study provided the basic data and theoretical basis for risk assessment of Sallmonella in China,and enriched the rapid detiction methods of foodbornes pathogens with resistance genes. |
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