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Co-integrate Col3m bla NDM-1-harboring plasmids in clinical Providencia rettgeri isolates from Argentina
Denise De Belder1,2, Florencia Martino1, Nathalie Tijet3
1Antimicrobial Agents Division, National and Regional Reference Laboratory in Antimicrobial Resistance (NRRLAR), National Institute of Infectious Diseases-ANLIS "Dr. Carlos G. Malbrán" , Buenos Aires, Argentina.
Importance:
Infections caused by carbapenem hydrolyzing enzymes like NDM (New Delhi metallo-beta-lactamase) represent a serious problem worldwide because they restrict available treatment options and increase morbidity and mortality, and treatment failure prolongs hospital stays. The first three cases of NDM in Argentina were caused by genetically related P. rettgeri recovered in two hospitals. In this work, we studied the genetic structure of the plasmids encoding bla NDM in those index cases and revealed the enormous plasticity of these genetic elements. In particular, we found a small plasmid that was also found inserted in the larger plasmids by homologous recombination as a co-integrate element. We also found that the bla NDM plasmids were not able to transfer or move to other hosts, suggesting their role as reservoir elements for the acquisition of resistance genes. It is necessary to unravel the dissemination strategies and the evolution of these resistant plasmids to find solutions to tackle their spread.
Insights
The first New Delhi metallo-beta-lactamase (NDM) in Argentina was found in Providencia rettgeri. These NDM-producing plasmids showed unusual genetic structures and were not transferable, highlighting the need for surveillance.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Carbapenem-resistant infections caused by New Delhi metallo-beta-lactamase (NDM) are a global health concern.
- The first cases of NDM-producing bacteria in Argentina were identified in 2013.
Purpose of the Study:
- To characterize the plasmids carrying the blaNDM gene in the initial NDM-positive Providencia rettgeri isolates from Argentina.
- To investigate the genetic environment and potential dissemination mechanisms of these NDM-encoding plasmids.
Main Methods:
- Hybrid assembly of short- and long-read sequencing data.
- Plasmid profiling using PFGE/S1-nuclease gel electrophoresis and Southern hybridization.
- In vitro conjugation assays to assess plasmid transferability.
Main Results:
- The blaNDM-1 gene was located on large (210–320 kb) chimeric Col3M plasmids in three genetically related Providencia rettgeri isolates.
- One isolate harbored an additional smaller plasmid capable of integrating into larger plasmids via homologous recombination.
- The identified NDM-plasmids were non-conjugative and lacked essential transfer genes (tra, oriT).
- Multiple antibiotic resistance genes, including blaPER-2, aph(3')-Ia, aph(3')-VI, qnrD1, aac(6´)Ib-cr, blaOXA-1, catB3, and arr3 within a class 1 integron, were present.
Conclusions:
- This study reports the first characterization of NDM-1-producing Providencia rettgeri in Argentina, revealing atypical plasmid structures and genetic environments.
- The non-conjugative nature of these plasmids suggests they may act as reservoirs for resistance genes rather than direct disseminators through conjugation.
- Continuous surveillance and study of these resistant plasmids are essential for understanding their evolution and developing strategies to combat their spread.
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