Abstract
A total of 26 blaIMP-4-carrying strains of Pseudomonas aeruginosa and Klebsiella pneumoniae were isolated from 2009 to 2013 in a Chinese teaching hospital, and these strains can be assigned into multiple sequence types or allelic profiles as determined by multilocus sequence typing. Of these strains, P. aeruginosa P378 and K. pneumoniae 1220 harbor the IMP-4-encoding plasmids pP378-IMP and p1220-IMP, respectively, whose complete nucleotide sequences are determined to be genetically closely related to the IncN1-type plasmid pIMP-HZ1. pP378-IMP/p1220-IMP-like plasmids are hinted to be present in all the other blaIMP-4-carrying strains, indicating the dissemination of pIMP-HZ1-related plasmids among K. pneumoniae or P. aeruginosa of different genotypes in this hospital. pP378-IMP carries two distinct accessory resistance regions, a blaIMP-4-carrying class 1 integron In823b, and a truncated Tn3-family unit transposon ΔTn6292-3′ harboring the quinolone resistance gene qnrS1. Massive fragmentation and rearrangement of these accessory genetic contents occur among p1220-IMP and IMP-HZ1 relative to pP378-IMP. blaIMP-4 is also present in the In823b remnants from p1220-IMP and IMP-HZ1, while qnrS1 is located in a Tn6292-derive fragment from pIMP-HZ1 but not found in p1220-IMP. pP378-IMP represents the first fully sequenced IncN-type plasmid from P. aeruginosa.
Highlights
Plasmids belonging to the IncN incompatibility group commonly have broad host range and high transmission efficiency, and they are important to the dissemination of clinically important resistance determinants among enterobacterial species
This study provides the evidence for dissemination of blaIMP-4-carrying pIMP-HZ1-related plasmids among K. pneumoniae or P. aeruginosa strains of different genotypes from 2009 to 2013 in a Chinese public hospital
Presence of blaIMP was detected by PCR in 19 (35.85%) strains of K. pneumoniae and in 7 (4.27%) strains of P. aeruginosa (Fig. 1), and all these detected blaIMP genes were blaIMP-4 as further determined by sequencing
Summary
PP378-IMP, p1220-IMP and pIMP-HZ1 possess the conserved IncN1-type backbone regions, which contain a repA gene and its iterons (RepA-binding sites; regulation of replication) for plasmid replication, the tra genes and kikA-korB for conjugal transfer, the CUP (conserved upstream repeat) -controlled regulon, the stbABC-orfD operon, and resP) for plasmid maintenance (Fig. 2). Multiple copies of IS26 are present in the In823b- and Tn6292-related regions of pP378-IMP, p1220-IMP and IMP-HZ1, and the common component IS26 would act as an adaptor[11,12] to mediate massive fragmentation and rearrangements of In823b- and Tn6292-related regions in p1220-IMP and IMP-HZ1 relative to pP378-IMP (Fig. 5), leaving different mosaic assemblies from the remnants of In823b and Tn6292 in p1220-IMP and IMP-HZ1 All these accessory genetic contents are integrated at two “hotspots” (Fig. 1), namely a region downstream of resP (resolvase) and a region within fipA (fertility inhibition protein), which has been previously described in IncN1 plasmids[2,4]. The qnrS1 gene was detected in 3 blaIMP-4-carrying K. pneumoniae strains and in 4 blaIMP-4-carrying P. aeruginosa strains (Table S1), denoting the probable coexistence of the In823-derived blaIMP-4 regions and the Tn6296-derived qnrS1 regions in these strains
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