An IncP-2 plasmid sublineage associated with dissemination of blaIMP-45 among carbapenem-resistant Pseudomonas aeruginosa

Abstract

IMP-45, a variant of IMP-9, is one of the dominant metallo-β-lactamases (MBLs) in clinical carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates in China. The aim of this study was to investigate the distribution and mechanism of dissemination of bla_IMP-45. MBL genes were detected by PCR in 173 non-duplicate CRPA isolates collected from Hospital HS in Shanghai and 605 P. aeruginosa isolates from a multicenter surveillance of bla_IMP-45 in China. In total, 17 IMP-45-producers (14 from Hospital HS and 3 from other hospitals) were identified. Molecular typing identified an outbreak of 11 IMP-45-producing ST508 CRPA in the ICU of Hospital HS. Conjugation assays and whole genome sequencing were conducted among IMP-45-producers. Genomic comparison revealed that 16 bla_IMP-45-carrying plasmids (9 from this study and 7 from GenBank) shared a similar backbone with IncP-2 bla_IMP-9-carrying plasmid pOZ176 but lacked repA-oriV-parAB region. repA2 gene was presented in pOZ176, bla_IMP-45-carrying plasmids (17 from this study and 7 from GenBank) and 15 megaplasmids from GenBank. Phylogenetic analysis of repA2 showed that most bla_IMP-45-carrying plasmids were clustered into a sublineage separate from the one containing pOZ176. This IncP-2 plasmid sublineage contributed to the dissemination of bla_IMP-45 among genetically diverse P. aeruginosa and recruited multiple resistance genes during its evolution.

Keywords: Carbapenem-resistant Pseudomonas aeruginosa; IncP-2 plasmid; blaIMP-45; dissemination; outbreak; sublineage.

Figure 1.

Twelve carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates carrying bla_IMP-45 at Hospital HS in 2015. (A) PFGE of 12 bla_IMP-45-bearing CRPA isolates. ST508 isolates belonged to pattern A and HS15-106 typed as pattern B. (B) Timeline of the first positive cultures of the bla_IMP-45-bearing CRPA isolates for the 12 patients. The blue triangle indicates the isolation date of the bla_IMP-45-carrying P. aeruginosa from ICU patients and the red indicates that of the outpatient.

Figure 2.

Genome comparison of plasmids containing a repA2 gene with IncP-2 plasmid pOZ176. This map was constructed with BRIG. The various colour levels indicate a BLAST result with sequence identity ranging from 80% to 100%. The inner red circle represents the pOZ176 reference sequence. The light green, dark green and purple circles (from innermost to outermost) indicate genome sequence of 7 bla_IMP-45-carrying megaplasmids in GenBank (p727-IMP, pA681-IMP, pBM413, pBM908, pPAG5, pR31014-IMP and pSY153-MDR), 9 bla_IMP-45-carrying plasmids in this study (pHS17-127, pRJ19-28, pHS15-101, pHS15-106, pHS15-158, pHS15-172, pKM18-18, pHS18-41 and pGZ18-2) and 16 completely sequenced megaplasmids harbouring repA2 in GenBank (pBT2101, pPABL048, AR441_unnamed3, AR_0356_unnamed2, RW109 plasmid 1, p12939-PER, pCF39S, pNK546-KPC, AR439_unnamed2, pRBL16, p1, pBT2436, p12969-DIM, pJB37 and pTTS12), respectively Backbone genes of pOZ176 are indicated in the figure.

Figure 3.

A maximum likelihood phylogenetic tree of 40 repA2 genes and features of their hosts. Red solid triangle, blue solid triangle and black solid square indicate bla_IMP-45-carrying plasmids in this study, 7 bla_IMP-45-carrying megaplasmids in GenBank and IncP-2 plasmid pOZ176, respectively. Resistance genes refer to β-lactamase genes, armA and qnrVC here. “N” denotes that the plasmid harbours no β-lactamase genes, armA or qnrVC.