Potential intrahospital dissemination ofPseudomonas aeruginosacarrying theblaIMP-1gene within a Tn7-like transposon

We aimed to determine the molecular characteristics of carbapenem-resistant Pseudomonas aeruginosa 18081308 and 18083286 isolated from the urine and sputum of two Chinese patients respectively, and analyzed the formation mechanism of the genetic environment in which it carries bla IMP-1 . Bacterial genome sequencing was carried out on strains 18081308 and 18083286 to obtain their whole genome sequence. Average nucleotide identity (ANI) was used for their precise species identification. Serotyping and multilocus sequence typing were performed. Furthermore, the acquired resistance genes, and virulence factors of these strains were identified. The carbapenem-resistant P. aeruginosa strains isolated in the present study were of sequence type ST865 and serotype O6. They all carried the same virulence factors (PLC, ExoSTY) and resistance genes ( aacC2 , tmrB , and bla IMP-1 ). Tn 6411 , a Tn 7 -like transposon carrying bla IMP-1 , was found in both strains. Detailed genetic dissection was applied to this transposon to display the genetic environment of bla IMP-1 . The aacC2 - tmrB region remnant-Tn 6411 backbone was the original structure of this type of transposon. A Tn 402 -like type 1 integron ( intl1 - aac(6’)-II - bla IMP-1 ) was inserted into it and formed a stable structure, which was localized in the chromosome by TnsD for transmission within P. aeruginosa ; the original structure of Tn 7 -like transposon was localized on the plasmid by TnsE for horizontal transmission between bacterial species. The intrahospital dissemination of P. aeruginosa ST865 isolated in this study was episodic. The bla IMP-1 -carrying Tn 7 -like transposon might enhance their ability to survive under drug selection pressure and aggravate the difficulty in treating infections.