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Published on: March 24, 2023
Evidence of structural rearrangements in ESBL-positive pESI(like) megaplasmids of S.Infantis
Patricia Alba1, Virginia Carfora1, Fabiola Feltrin1
1National Reference Laboratory for Antimicrobial Resistance, Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostics Department, Rome 00178, Italy.
Abstract:
The increasing prevalence of pESI(like)-positive, multidrug-resistant (MDR) S. Infantis in Europe is a cause of major concern. As previously demonstrated, the pESI(like) megaplasmid is not only a carrier of antimicrobial resistant (AMR) genes (at least tet, dfr, and sul genes), but also harbours several virulence and fitness genes, and toxin/antitoxin systems that enhance its persistence in the S. Infantis host. In this study, five prototype pESI(like) plasmids, of either CTX-M-1 or CTX-M-65 ESBL-producing strains, were long-read sequenced using Oxford Nanopore Technology (ONT), and their complete sequences were resolved. Comparison of the structure and gene content of the five sequenced plasmids, and further comparison with previously published pESI(like) sequences, indicated that although the sequence of such pESI(like) 'mosaic' plasmids remains almost identical, their structures appear different and composed of regions inserted or transposed after different events. The results obtained in this study are essential to better understand the plasticity and the evolution of the pESI(like) megaplasmid, and therefore to better address risk management options and policy decisions to fight against AMR and MDR in Salmonella and other food-borne pathogens. Graphical representation of the pESI-like plasmid complete sequence (ID 12037823/11). Block colours indicate the function of the genes: red: repB gene; pink: class I integrons (IntI); yellow; mobile elements; blue: resistance genes; green: toxin/anti-toxin systems; grey: mer operon; light green: genes involve in conjugation.
Insights
The pESI(like) megaplasmid, found in multidrug-resistant Salmonella Infantis, shows structural variations despite conserved gene sequences. Understanding its evolution is key to combating antimicrobial resistance in foodborne pathogens.
Area of Science:
- Microbiology
- Genomics
- Molecular Biology
Background:
- The pESI(like) megaplasmid is increasingly prevalent in multidrug-resistant (MDR) Salmonella Infantis strains across Europe.
- This megaplasmid carries antimicrobial resistance (AMR) genes, virulence factors, and toxin/antitoxin systems, enhancing bacterial persistence.
Purpose of the Study:
- To fully sequence and analyze the structure of five prototype pESI(like) plasmids from ESBL-producing S. Infantis strains.
- To compare these sequences with existing pESI(like) plasmids to understand their structural plasticity and evolution.
Main Methods:
- Long-read sequencing using Oxford Nanopore Technology (ONT) to resolve complete plasmid sequences.
- Comparative genomics to analyze structural differences and gene content.
Main Results:
- Complete sequences of five pESI(like) plasmids were obtained.
- Analysis revealed that while the gene sequences of these 'mosaic' plasmids are highly conserved, their structures exhibit significant differences due to inserted or transposed regions.
- These structural variations arise from different insertion and transposition events.
Conclusions:
- The pESI(like) megaplasmid demonstrates considerable structural plasticity and evolutionary dynamics.
- Understanding these evolutionary mechanisms is crucial for developing effective risk management strategies against MDR foodborne pathogens like Salmonella.
