IncX2 and IncX1-X2 Hybrid Plasmids Coexisting in a FosA6-Producing Escherichia coli Strain

Abstract

IncX plasmids are receiving much attention as vehicles of carbapenem and colistin resistance genes, such as bla NDM , bla KPC , and mcr-1. Among them, IncX2 subgroup plasmids remain rare. Here, we characterized IncX2 and IncX1-X2 hybrid plasmids coexisting in a FosA6-producing Escherichia coli strain that were possibly generated as a consequence of recombination events between an R6K-like IncX2 plasmid and a pLN126_33-like IncX1 plasmid. Variable multidrug resistance mosaic regions were observed in these plasmids, indicating their potential to serve as flexible carriers of resistance genes. The diversity of IncX group plasmid backbones and accessory genes and the evolution of hybrid IncX plasmids pose a challenge in detecting and classifying them.KEYWORDS IncX plasmid, taxC, pir, genotyping, glutathione synthetase T he IncX family plasmids are narrow-host-range plasmids mostly found in Enterobacteriaceae (1-3). IncX plasmids contain a highly syntenic backbone consisting of core genes responsible for plasmid replication, partitioning, maintenance, and conjugal DNA transfer (2). So far, at least eight subgroups of IncX plasmids have been reported, IncX1 to IncX8, carrying various resistance genes, including oqxAB, qnrS1, qnrS2, bla TEM , bla SHV , bla CTX-M , bla KPC , bla NDM , and mcr-1, and mediating resistance to fluoroquinolones, cephalosporins, carbapenems, colistin, or other types of antibiotics (2-9). Plasmid R6K, recovered from an Escherichia coli strain cultured in Greece in the 1960s, is considered to be the prototypical IncX plasmid (1). R6K belongs to a rare IncX subgroup, IncX2, with only two other currently recognized members, pNGX2-QnrS1 (GenBank accession number JQ269335.1) and pEBG1 (GenBank accession number KF738053.1), both discovered in strains from western Nigeria and carrying qnrS1 genes (3, 10). In contrast, the IncX1, IncX3, and IncX4 subgroup plasmids are much more prevalent and are associated with oqxAB, bla NDM , respectively (2,3,7,8,11). Here, we describe a new IncX2 plasmid, pYD786-4, that coexisted with a hybrid IncX1-X2 plasmid pYD786-3 in an E. coli ST410 urinary tract strain collected from a patient in the United States (12). RESULTS AND DISCUSSIONHybrid IncX1-X2 plasmid pYD786-3. Plasmid pYD786-3 is 44,806 bp in size and shares conserved backbone modules of both IncX1 and IncX2 plasmids. The replication, partitioning, and stability regions are from the IncX1 plasmid, while the maintenance and DNA transfer regions are from the IncX2 plasmid (Fig. 1). pir and bis encode the plasmid initiation replication protein and auxiliary protein that bind to the core region of replication gamma origin (2). parGF and stbED have putative functions of partitioning and stability. Two long inverted repeats (LIRs), ␣-LIR and ␤-LIR, contain origins of

<p>Clinical and Molecular Epidemiologic Characteristics of Ceftazidime/Avibactam-Resistant Carbapenem-Resistant <em>Klebsiella pneumoniae</em> in a Neonatal Intensive Care Unit in China</p>

“…Zhang, Humphries et al suggest this may be due to overexpression of the bla KPC gene. 26 , 35 Nevertheless, this will require further study in the future to address any potential mechanisms of CZA-resistant CRKP-producing KPC. 36…”

Mobile Genetic Elements Associated with Antimicrobial Resistance

“…[except for IncX3(pEC14)] (170). An X3/X4 hybrid plasmid, apparently generated by formation and resolution of an X3-X4 cointegrate (292), and an X1/X2 hybrid (293) have also been identified.…”

<p>Reversal of <em>mcr-1</em>-Mediated Colistin Resistance in <em>Escherichia coli</em> by CRISPR-Cas9 System</p>

“…17 The emergence and dissemination of colistin resistance mcr-1 raise a great challenge to the treatment of clinical infections. Since the first report of mcr-1 in IncI2-type plasmid pHNSHP45, a series of mcr-1-carrying plasmids have been detected, including IncHI2, 18 IncX4, 19 IncX2, 20 IncP, 21 IncII, 22 and other. 3,23 The plasmids can act as reservoirs of horizontal gene transfer.…”