Study On Optimal Detection Method And Antimicrobial Resistance Mechanism Of Vibrio Vulnificus In Food

Vibrio vulnificus,widely exists in marine water and food,is one of the top three pathogenic Vibrios and a serious threat to food safety and public health.In China,there is no standard method has developed for detecting Vibrio vulnificus in food.Meanwhile,the prevalence of Vibrio vulnificus and its characteristics are not clear yet.In this study,the detection method of Vibrio vulnificus in food were optimized and the prevalence of Vibrio vulnificus in food was investigated.The pathogenesis and antimicrobial resistance mechanism were studied via whole genome sequencing technology.The main results are as follows:(1)A method for Vibrio vulnificus detection in China was established.The basic procedure is:sample→PNCC broth enrichment→PCR screening→CC and m CPC recovering→PCR identification.The detection limit is×10~1CFU/25g.Biolog analysis showed that Vibrio vulnificus grows better in N-acetyl-D-galactosamine,β-methyl-D-galactosidase,α-ketoglutarate than Vibrio parahaemolyticus or Vibrio alginolyticus,the tolerance of nafcillin,potassium tellurite,poly lysine,5-nitro-2-furfural semicarbazone was significantly better than the latters.(2)The prevalence of Vibrio vulnificus in aquatic product was investigated using the optimizated method in Beijing,the results showed that the overall detection rate was 14.10%,of which the prevalence rate to shrimp is 34.78%,followed by to shellfish,the contamination rate of which was 17.11%.All 81 Vibrio vulnificus strains resisted to cefazolin,the rates of resistant isolates to ampicillin,amoxicillin/clavulanate,cefotaxime,ceftazidime,gentamicin,cotrimoxazole resistance were same as 1.23%.All strains were vcg C,and 76(93.83%)were16S r RNA B and 5(6.17%)were 16S r RNA AB after the isolates were subtyped by 16S r RNA,no biological 2 or serum E type was found.(3)The whole genome sequencing method was used to explore the resistance mechanism of Vibrio vulnificus.No antibiotic resistance gene in the genome was found that corresponding to the resistant phenotype.mutations were detected in omp U,however,they were subsequently verified as silent mutation.The resistance of Vibrio vulnificus was irrelevant with antimicrobial resistance genes and mutation of ompU.