IncFIB-4.1 and IncFIB-4.2 Single-Replicon Plasmids: Small Backbones with Large Accessory Regions.

Purpose: To establish a typing scheme for IncFIB replicon and to dissect genomic features of IncFIB-4.1/4.2 single-replicon plasmids. Methods: A total of 146 representative fully sequenced IncFIB-replicon-containing plasmids were selected to construct a phylogenetic tree of repB IncFIB sequences. A collection of nine IncFIB-4.1/4.2 single-replicon plasmids from China were fully sequenced here and compared with the first sequenced IncFIB-4.1/4.2 single-replicon plasmids from GenBank to dissect their genomic diversity. Results: In this study, a repB sequence-based scheme was proposed for grouping IncFIB replicon into seven primary types and further into 70 subtypes. A collection of nine IncFIB-4.1/4.2 single-replicon plasmids were fully sequenced here and compared with the first sequenced IncFIB-4.1/4.2 single-replicon plasmids from GenBank. These 11 plasmids had small backbones and shared only three key backbone markers repB together with its iterons, parABC, and stbD. Each plasmid contained one large accessory region (LAR) inserted into the backbone, and these 11 LARs had significantly distinct profiles of mobile genetic elements (MGEs) and resistance/metabolism gene loci. Antibiotic resistance regions (ARRs; the antibiotic resistance gene-containing genetic elements) were found in seven of these 11 LARs. Besides resistance genes, ARRs carried unit or composite transposons, integrons, and putative resistance units. IncFIB-4.1/4.2 single-replicon plasmids were important vectors of drug resistance genes. This was the first report of three novel MGEs: In1776, Tn6755, and Tn6857. Conclusion: Data presented here provided a deeper insight into diversity and evolution of IncFIB replicon and IncFIB-4.1/4.2 single-replicon plasmids.

Plasmids of novel incompatibility group IncpRBL16 from Pseudomonas species.

OBJECTIVES: To dissect genomic features of IncpRBL16 plasmids from Pseudomonas. METHODS: An extensive genomic comparison was applied to all 17 available sequenced IncpRBL16 plasmids, including 8 sequenced in this study and another 2 sequenced in two of our previous studies. RESULTS: Conserved IncpRBL16 backbone markers repAIncpRBL16 together with its iterons, parB2-parA, che, pil and ter were present in all 17 plasmids. At least 18 regions or sites across IncpRBL16 genomes exhibited major modular differences, including insertion of accessory modules, deletion of backbone regions surrounding insertion sites and substitution of multiple-gene backbone regions. Ten plasmids carried a sole IncpRBL16 replicon, while exogenous acquisition of an auxiliary replicon (located in an accessory module) besides the primary IncpRBL16 replicon was observed in each of the remaining seven plasmids. The 17 IncpRBL16 plasmids carried at least 71 different accessory modules, notably including Tn1403-related regions, Tn7-family transposons, Tn6571-family transposons, integrative and conjugative elements, and integrative and mobilizable elements. There were a total of 40 known resistance genes, which were involved in resistance to 15 categories of antibiotics and heavy metals, notably including blaIMP-9, blaIMP-45, blaVIM-2, blaDIM-2, blaOXA-246, blaPER-1, aphA and armA. CONCLUSIONS: Different IncpRBL16 plasmids contain different profiles of accessory modules and thus diverse collections of resistance genes. To the best of our knowledge, this is the first report of fully sequenced blaOXA-246-carrying (p12939-PER) and blaPER-1-carrying (p12939-PER and pA681-IMP) IncpRBL16 plasmids and also that of 14 novel (first identified in this study) and additionally 31 newly named (first designated in this study, but with previously determined sequences) mobile elements.

Type 1, 2, and 1/2-Hybrid IncC Plasmids From China.

A collection of 11 IncC plasmids from China were fully sequenced herein and compared with reference plasmids pR148 and pR55. These 13 plasmids could be assigned into three different subgroups: type 1, type 2, and type 1/2 hybrid. Type 1/2-hybrid plasmids most likely emerged from homologous recombination between type 1 and type 2 plasmids. Different IncC plasmids had evolved to acquire quite different profiles of accessory modules and thus different collections of resistance genes. The accessory resistance modules included not only the bla CMY-carrying region, the ARI-A island, and the ARI-B island, but also various additional kinds of resistance islands such as the bla CTX-M-carrying regions and the MDR regions. Insertion of accessory modules was sometimes accompanied by deletion, inversion, and translocation of surrounding backbone regions. pR148 and pR55 were confirmed to have the most complete backbones for type 1 and type 2, respectively. This was the first report of a bla IMP- 8-carrying IncC plasmid, and that of three novel mobile elements: a Tn1696-derived unit transposon Tn6395, a class 2 integron In2-76, and an insertion sequence ISEcl10.

First Report of Coexistence of Three Different MDR Plasmids, and That of Occurrence of IMP-Encoding Plasmid in Leclercia adecarboxylata.

Three different MDR plasmids p16005813A, p16005813B, and p16005813C, which carried a total of 18 non-redundant resistance genes or gene loci, were identified in a single clinical isolate of Leclercia adecarboxylata. The p16005813A backbone showed very low levels of identity to all DNA sequences available in public databases and carried a repA gene that could not assigned into any of known incompatibility groups. The IncFII-family p16005813B and pECAZ161_KPC had essentially identical backbones. p16005813C belonged to an IncR single-replicon plasmid. p16005813A, p16005813B, and p16005813C harbored three different novel MDR regions as their sole accessory modules. The MDR region of p16005813B manifested as Tn6505, which was generated from insertion of bla IMP-8-carrying In655 instead of In4 into the Tn1696 backbone. Other key antibiotic resistance elements included Tn2, IS26-mph(A)-mrx-mphR(A)-IS6100 unit, chrA region, In27, and aacC2-tmrB region in the MDR region of p16005813A, and ΔTn9 carrying catA1, In609, and IS26-tetA(C)-tetR(C)-IS26 unit in the MDR region of p16005813C. This was the first report of coexistence of three different MDR plasmids, and that of occurrence of IMP-encoding plasmid and bla IMP-8 gene in L. adecarboxylata.

Characterization of the plasmid of incompatibility groups IncFIIpKF727591 and IncpKPHS1 from Enterobacteriaceae species.

BACKGROUND: Multiple incompatibility (Inc) groups of plasmids have been identified in Enterobacteriaceae species, but there are still quite a few sequenced plasmids that could not be assigned to any known Inc groups. METHODS: One IncFIIpKF727591ß plasmid p205880-qnrS and two IncpKPHS1 plasmids p11219-CTXM and p205880-NR1 were fully sequenced in this work. Detailed genomic comparison was applied to all available sequenced plasmids of IncFIIpKF727591 or IncpKPHS1 group. RESULTS: p205880-qnrS carried a novel transposon Tn6396, which was an ISKpn19-compsite transposon and represented a prototype transposable element carrying a minimum core qnrS1 module. p11219-CTXM harbored a novel transposon Tn6559, which was generated from integration of a truncated IS903D-bla CTX-M-14 -ISEcp1 unit into the Tn3-family cryptic unit transposon Tn1722. Two Inc groups, IncFIIpKF727591 and IncpKPHS1, of plasmids from Enterobacteriaceae species were proposed, and IncFIIpKF727591 was further grouped into two subgroups IncFIIpKF727591α and IncFIIpKF727591ß. Each of the 11 IncFIIpKF727591 plasmids carried multiple accessory modules including at least one resistance module, and the relatively small IncFIIpKF727591 backbones could acquire a wealth of foreign genetic contents. The modular structures of plasmid backbones were conserved within each of IncFIIpKF727591α and IncFIIpKF727591ß subgroups but dramatically different, although with similar gene organizations, between these two subgroups. The IncpKPHS1 backbones were conserved with respect to modular structures, and only four of the 14 IncpKPHS1 plasmids carried accessory modules, two of which contained resistance genes. CONCLUSION: A genomic comparison of sequenced IncpKPHS1 or IncFIIpKF727591 plasmids provides insights into modular differences and genetic diversification of these plasmids, some of which carries antimicrobial resistance genes.