Sequencing of the blaIMP-4 -carrying C. freundii B38 using PacBio SMRT technique revealed that the genome contained a chromosome of 5,134,500 bp, and three plasmids, pOZ172 (127,005 bp), pOZ181 (277,592 bp), and pOZ182 (18,467 bp). Plasmid pOZ172 was identified as IncFIIY, like pP10164-NDM and pNDM-EcGN174. It carries a class 1 integron with four cassettes: blaIMP-4-qacG2-aacA4-aphA15, and a complete hybrid tni module (tniR-tniQ-tniB-tniA). The recombination of tniR from Tn402 (identical) with tniQBA (99%) from Tn5053 occurred within the res site of Tn402/5053. The Tn402/5053-like integron, named Tn6017, was inserted into Tn1722 at the res II site. The replication, partitioning and transfer systems of pOZ181 were similar to IncHI2 (e.g. R478) and contained a sul1-type class 1 integron with the cassette array: orf-dfrA1-orf-gcu37-aadA5 linked to an upstream Tn1696 tnpA-tnpR and to a downstream 3' CS and ISCR1 A Tn2 transposon with a blaTEM-1b ß-lactamase was identified on pOZ182. Other interesting resistance determinants on the B38 chromosome included MDR efflux pumps, AmpC ß-lactamase, and resistances to Cu, Ag, As, and Zn. This is the first report of a complete tni module linked to a blaIMP- 4 carrying class 1 integron, and together with other recently reported non-sul1 integrons, represents the emergence of a distinct evolutionary lineage of class 1 integrons lacking a 3' -CS (qacE?1-sul1). The unique cassette array, complete tni module of Tn6017, and incompatibility group of pOZ172 suggests a different blaIMP-4 evolutionary pathway in C. freundii B38 compared to other blaIMP-4 foundin Gram-negative bacteria in the Western Pacific Region. Copyright © 2016, American Society for Microbiology. All Rights Reserved.
Journal: Antimicrobial agents and chemotherapy