Co-occurrence of 3 different resistance plasmids in a multi-drug resistant Cronobacter sakazakii isolate causing neonatal infections.

Cronobacter sakazakii 505108 was isolated from a sputum specimen of a neonate with severe pneumonia. C. sakazakii 505108 co-harbors 3 resistance plasmids of the IncHI2, IncX3, and IncFIB incomparability groups, respectively. These 3 plasmids have acquired several accessory modules, which carry an extremely large number of resistance genes, especially including those involved in resistance to carbapenems, aminoglycoside, tetracyclines, and phenicols and sulphonamide/trimethoprim. These plasmid-borne antibiotic resistance genes were associated with insertion sequences, integrons, and transposons, indicating that the assembly and mobilization of the corresponding accessory modules with complex chimera structures are facilitated by transposition and/or homologous recombination. This is the first report of fully sequence plasmids in clinical Cronobacter, which provides a deeper insight into plasmid-mediated multi-drug resistance in Cronobacter from hospital settings.

Sequencing and Genomic Diversity Analysis of IncHI5 Plasmids.

IncHI plasmids could be divided into five different subgroups IncHI1-5. In this study, the complete nucleotide sequences of seven bla IMP- or bla VIM-carrying IncHI5 plasmids from Klebsiella pneumoniae, K. quasipneumoniae, and K. variicola were determined and compared in detail with all the other four available sequenced IncHI5 plasmids. These plasmids carried conserved IncHI5 backbones composed of repHI5B and a repFIB-like gene (replication), parABC (partition), and tra1 (conjugal transfer). Integration of a number of accessory modules, through horizontal gene transfer, at various sites of IncHI5 backbones resulted in various deletions of surrounding backbone regions and thus considerable diversification of IncHI5 backbones. Among the accessory modules were three kinds of resistance accessory modules, namely Tn10 and two antibiotic resistance islands designated ARI-A and ARI-B. These two islands, inserted at two different fixed sites (one island was at one site and the other was at a different site) of IncHI5 backbones, were derived from the prototype Tn3-family transposons Tn1696 and Tn6535, respectively, and could be further discriminated as various intact transposons and transposon-like structures. The ARI-A or ARI-B islands from different IncHI5 plasmids carried distinct profiles of antimicrobial resistance markers and associated mobile elements, and complex events of transposition and homologous recombination accounted for assembly of these islands. The carbapenemase genes bla IMP-4, bla IMP-38 and bla VIM-1 were identified within various class 1 integrons from ARI-A or ARI-B of the seven plasmids sequenced in this study. Data presented here would provide a deeper insight into diversification and evolution history of IncHI5 plasmids.

Comparative genomics of type 1 IncC plasmids from China.

AIM: This study dealt with genomic characterization of type 1 IncC resistance plasmids, capable of spreading across taxonomic borders, from China. MATERIALS & METHODS: p112298-tetA was sequenced and compared with type 1 IncC reference plasmid pR148 and two available sequenced type 1 IncC plasmids pHS36-NDM and pVAS3-1 from China. RESULTS: These plasmids contained one or more exogenous resistance islands, which included the ARI-A islands, the ARI-B islands, the ISEcp1-blaCMY units and the bla KPC-2 region and were inserted at various sites in the IncC backbone and thus represented three distinct lineages. CONCLUSION: Complex rearrangement and homologous recombination events have occurred during evolution of p112298-tetA, making it significantly differ modularly from the other three plasmids with respect to both plasmid backbone and exogenous resistance regions.

Sequencing and comparative genomics analysis of the IncHI2 plasmids pT5282-mphA and p112298-catA and the IncHI5 plasmid pYNKP001-dfrA.

Incompatibility group IncHI plasmids are important vectors of antibiotic resistance in Enterobacteriaceae. In this study, a scheme for typing IncHI into five separately clustering subgroups, including previously designated IncHI1-3 as well as IncHI4-5, was proposed based on sequenced IncHI plasmids. The complete nucleotide sequences of the IncHI2 plasmids pT5282-mphA and p112298-catA and the IncHI5 plasmid pYNKP001-dfrA from clinical Enterobacter cloacae, Citrobacter freundii and Raoultella ornithinolytica isolates, respectively, were determined and were compared with IncHI2 and IncHI5 reference plasmids. Considerable genetic conservation was observed within the backbone sequences of each of the IncHI2 and IncHI5 subgroups, but the backbone sequences of the two subgroups were dramatically different from each other. However, the conjugal transfer regions tra1 and tra2 as well as the tellurium resistance gene cluster ter were present in all five plasmids. A number of accessory regions associated with integrons, transposons and insertion sequence-based mobile elements have been inserted at various sites of the plasmid backbones, among which were several large regions harbouring genes conferring resistance to multiple classes of antibiotics. Data generated from this study provide us with a deeper understanding of the diversification of IncHI-type resistance plasmids.