The Study Of Resistant Molecular Epidemiology Of Salmonella Enterica Serotype Kentucky In China

Salmonella is one of the important zoonotic pathogens and one of the most important pathogens causing foodborne diseases worldwide.About 93.8 million cases of salmonellosis occur worldwide each year.To date,more than 2,600 Salmonella serotypes have been discovered in the world.The outbreak of some special Salmonella serotypes has caused great economic losses and health threats,its infection treatment problem has put forward higher requirements for the use of antibiotics.Salmonella kentucky in the Lancet magazine reported that is a high-risk Salmonella serotype with high ciprofloxacin resistance and rapid crosspopulation of human and animal hosts in 2012.There is no systematic research about Salmonella Kentucky in China,so the research on Salmonella in Kentucky has great significance for the regulation and prevention of foodborne pathogens in China.In this study,drug sensitivity analysis and drug molecular characteristics of Salmonella Kentucky 191 strains isolated from clinical cases and the supply chain of poultry from 2013 to 2016 were analysed in China.The drug sensitivity results showed that the multi-drug resistance rate of Salmonella in Kentucky is as high as 79.63%.Among them,Salmonella Kentucky showed resistance to human first-line clinical drugs(ciprofloxacin,cefotaxime),and the drug resistance rate is 39.27% and 7.85%,respectively.The 191 strains of Salmonella Kentucky were analyzed by multilocus sequence typing(MLST),and the diversity of Salmonella Kentucky was found to be more complicated.There are 8 ST types were found,of which ST314(n=117)and ST198(n=67)are dominated.In addition,Salmonella Kentucky ST17 strains reported in cows and ST152 found commonly in American poultry,them are also found in China.After multi-locus sequencing,the resistance of Salmonella Kentucky ST314 and ST198 are significantly different in the resistance rates of ciprofloxacin and cefotaxime in China.The quinolone resistance-determining region(QRDR)mutation and the plasmid-mediated quinolone resistance gene(PMQR)are examined.The mutation rate of the quinolone resistance-determining region(QRDR)of Salmonella Kentucky ST198 is much higher than that of ST314.The mutation diversity(double mutation,triple mutation)of the quinolone resistance-determining region to Salmonella Kentucky ST198 is more complicated.The quinolone resistance of Salmonella Kentucky ST314 are mainly reflected in the plasmidmediated quinolone resistance gene(PMQR).The experiment with the drug resistance of cephalosporins by ESBLs genotype detection,bla TEM-1 was the major ESBLs gene(16/191,8.38%),followed by bla CTX-M-55(6/191),3.14%)and bla OXA-1(3/191,1.57%).In terms of ESBLs genetic diversity and detection rate,Salmonella Kentucky ST198 is higher than that of Salmonella Kentucky ST314.The pulse-field gel electrophoresis(PFGE)typing method was used to study the homology of Salmonella.After PFGE typing,there were mainly 2 clusters(Salmonella Kentucky ST314 and ST198 strains)are found in China.To the PFGE subtypes,15 of the PFGE subtypes contain only a single polymer,and 23 of the PFGE subtypes consist of 2 to 53 aggregates.According to the PFGE map,there is a high degree of homology with Salmonella Kentucky ST314 and ST198 between the poultry food source and the human strain.In summary,Chinese popular Salmonella Kentucky ST type based mainly on Kentucky ST198 and Kentucky ST314 strains,which are widely distributed in humans,poultry and food,those strains have resistance to quinolones and cefotaxime,and The risk of cross-host transmission between human and poulty food.There are different quinolone resistance mechanisms from different Salmonella kentucky ST-type.The main cause of the quinolone resistance of Salmonella kentucky ST198 is due to the mutation of the quinolone resistance determining region(QRDR);the quinolone resistance with Salmonella kentucky ST314 strain because gene(PMQR)mediated in the plasmid.This study hopes to provide an effective reference for the prevention and control of Salmonella kentucky by molecular epidemiological studies.