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Identification and Characterisation of pST1023 A Mosaic, Multidrug-Resistant and Mobilisable IncR Plasmid
Carla Calia1, Marta Oliva1, Massimo Ferrara2
1Department of Biology, University of Bari, Via Orabona, 4, 70125 Bari, Italy.
Abstract:
We report the identification and characterisation of a mosaic, multidrug-resistant and mobilisable IncR plasmid (pST1023) detected in Salmonella ST1023, a monophasic variant 4,[5],12:i: strain of widespread pandemic lineage, reported as a Southern European clone. pST1023 contains exogenous DNA regions, principally gained from pSLT-derivatives and IncI1 plasmids. Acquisition from IncI1 included oriT and nikAB and these conferred the ability to be mobilisable in the presence of a helper plasmid, as we demonstrated with the conjugative plasmids pST1007-1D (IncFII) or pVC1035 (IncC). A sul3-associated class 1 integron, conferring resistance to aminoglycosides, chloramphenicol and trimethoprim-sulphonamides, was also embedded in the acquired IncI1 DNA segment. pST1023 also harboured an additional site-specific recombination system (rfsF/rsdB) and IS elements of the IS1, IS5 (IS903 group) and IS6 families. Four of the six IS26 elements present constituted two pseudo-compound-transposons, named PCT-sil and PCT-Tn10 (identified here for the first time). The study further highlighted the mosaic genetic architecture and the clinical importance of IncR plasmids. Moreover, it provides the first experimental data on the ability of IncR plasmids to be mobilised and their potential role in the horizontal spread of antimicrobial-resistant genes.
Insights
We identified a multidrug-resistant IncR plasmid in Salmonella ST1023, revealing its mosaic structure and mobilisable nature. This discovery highlights the role of IncR plasmids in spreading antimicrobial resistance genes.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Salmonella ST1023 is a monophasic variant strain belonging to a pandemic lineage.
- Antimicrobial resistance is a significant global health concern, often mediated by plasmids.
- IncR plasmids are a class of plasmids whose genetic characteristics and role in antimicrobial resistance dissemination are not fully understood.
Purpose of the Study:
- To identify and characterize a novel IncR plasmid (pST1023) from Salmonella ST1023.
- To investigate the genetic makeup of pST1023, including acquired DNA regions and mobile genetic elements.
- To determine the mobilisable potential of IncR plasmids and their contribution to the spread of antimicrobial resistance.
Main Methods:
- Plasmid DNA isolation and characterization.
- Whole-genome sequencing and bioinformatic analysis.
- Conjugation experiments to assess plasmid mobility using helper plasmids.
Main Results:
- Identification of a mosaic IncR plasmid, pST1023, in Salmonella ST1023.
- pST1023 contains acquired DNA from pSLT-derivatives and IncI1 plasmids, including an oriT and nikAB region conferring mobilisability.
- A sul3-associated class 1 integron conferring resistance to multiple antibiotics was identified within the acquired IncI1 DNA.
- The plasmid harbors various insertion sequence (IS) elements and two novel pseudo-compound-transposons (PCT-sil and PCT-Tn10).
- Experimental evidence demonstrated that pST1023 is mobilisable in the presence of conjugative helper plasmids.
Conclusions:
- IncR plasmids possess a mosaic genetic architecture and are clinically important.
- pST1023 is mobilisable, indicating a potential role for IncR plasmids in the horizontal gene transfer of antimicrobial resistance.
- This study provides the first experimental data on IncR plasmid mobilisability and their contribution to antimicrobial resistance spread.
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