Sequencing And Comparative Genomics Analysis Of The IncHI2 Plasmids PT5282-mphA And P112298-catA And The IncHI5 Plasmid PYNKP001-dfrA

In recent years,multiple drug-resistant strains and pan-resistant strains emerge and spread faster,further increases the difficulty of treatment about clinical infectious diseases.Plasmids carrying drug-resistant gene play an important role to the dissemination of drug-resistant bacteria.Resistant genes were transferred horizontally through integrons,transposons,and insertion sequence-based mobile elements,which were carried by plasmid.Plasmid can mediate the transfer of drug-resistant genes in different bacterial individuals,while the other three can only mediate the inter-molecular transfer of drug-resistant genes in inner bacterial individuals.IncHI plasmids are important vectors of antibiotic resistance in Enterobacteriaceae.In this study,a scheme for typing IncHI into five separately-clustering subgroups,including previously designated IncHI1-3,as well as IncHI4-5,was proposed based on sequenced IncHI plasmids.The complete nucleotide sequences of IncHI2 plasmids pT5282-mphA and p112298-catA and IncHI5 plasmid pYNKP001-dfrA from clinical Enterobacter cloacae,Citrobacter freundii,and Raoultella ornithinolotica isolates,respectively,were determined and compared with the IncHI2 and IncHI5 reference plasmids.Considerable genetic conservation was observed within the backbone sequences of each of the IncHI2 and IncHI5 subgroups,but the backbone sequences of the two subgroups were dramatically different from each other.However,the conjugal transfer regions tral and tra2,as well as the tellurium resistance gene cluster ter,were present in all five plasmids.A number of accessory regions associated with integrons,transposons,and insertion sequence-based mobile elements have been inserted at various sites of the plasmid backbones,among which were several large regions harboring genes conferring resistance to multiple classes of antibiotics,accounting for resistance to aminoglycosides,chloramphenicols,tetracyclines,P-lactam antibiotics,macrolides,sulphonamide,fluoroquinolones,rifampicin,trimethoprim,fosfomycin and quaternary ammonium.In the process of understanding the fine structure about multiple-drug-resistance plasmids,a number of novel mobile elements have been discovered,seven novel transposons(Tn6321,Tn6322,Tn6338-Tn6340,Tn6346?Tn6347);eight novel insertion sequences(ISEc16,ISCfr8-ISCfr11,ISKox1-ISKox3).After antibiotics used in clinical treatment of infectious disease,drug-resistant bacteria appeared.Antibiotic selection pressure and changeable environmental conditions denotes its rapid evolution and its potent ability to acquire and keep different resistance genes,which will facilitate its dissemination and persistence under different antimicrobial selection pressures.A scheme for typing the incompatibility group IncHI into five separately-clustering subgroups IncHI1-5 was proposed.Data generated from this study provides us with a deeper understanding of the diversification of IncHI-type resistance plasmids,implicated IncHI plasmids as important vectors in the dissemination of multidrug resistance among clinical isolates.Not only can provide the molecular basis for the clinical treatment of infectious diseases,and can also improve the awareness of the prevention and control the dissemination of multidrug resistant bacteria.Future surveillance and epidemiological studies are needed to evaluate multidrug resistant bacteria,to provide the basis for evidence-based medicine for early medication experience.