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An NDM-1-Producing Acinetobacter towneri Isolate from Hospital Sewage in China
Kaiying Wang1,2, Peihan Li1,2, Jinhui Li2
1College of Military Medicine, Academy of Military Sciences, Beijing, People's Republic of China.
Background:
The New Delhi metallo-β-lactamase-1 (NDM-1)-positive plasmid and its variants pose daunting threats to public health. Hospital sewage was considered as an important reservoir of antibiotic genes. Numerous and diverse taxa of multidrug-resistant (MDR) bacteria carrying NDM-1-positive plasmids have been identified during routine surveillance of hospital sewage. We herein report a carbapenem-resistant Acinetobacter towneri strain AeBJ009 with an NDM-1-positive plasmid isolated from hospital sewage.
Materials And Methods:
Bacteria were isolated from cultures of hospital sewage and identified by using the Vitek 2 compact system and 16S rRNA sequencing. The bla gene was amplified and confirmed by sequencing. Antimicrobial susceptibility testing was performed using AST-GN14 on the Vitek2 compact system. In addition, the bla gene was located by Southern blotting. Conjugation experiment and whole-genome sequencing were performed for further analysis.
Results:
Strain AeBJ009 was isolated from hospital sewage and identified as A. towneri. Antimicrobial susceptibility testing revealed an MDR phenotype. Pulsed-field gel electrophoresis and Southern blotting showed that strain AeBJ009 carries three plasmids and that bla is located on the 47kb plasmid pNDM-AeBJ009. However, the conjugation experiment to transfer pNDM-AeBJ009 to Escherichia coli strain J53 was unsuccessful. Whole-genome sequencing found that pNDM-AeBJ009 contains a Tn125 element carrying bla . The ble gene downstream of bla displayed a single-nucleotide polymorphism compared to its homologue on plasmid pM131_NDM1. BLAST analysis using the Comprehensive Antibiotic Resistance Database identified no gene polymorphisms with 100% identity to our ble variant.
Conclusion:
The A. towneri strain AeBJ009 exhibiting an extended spectrum of antibiotic resistance was isolated from hospital sewage and may potentially exacerbate the risk of MDR bacterial infections. The prevention of nosocomial infections due to drug-resistant bacteria will require enhanced monitoring and control of MDR pathogens in environmental reservoirs.
Insights
A carbapenem-resistant Acinetobacter towneri strain carrying a New Delhi metallo-β-lactamase-1 (NDM-1) plasmid was identified in hospital sewage. This finding highlights the potential for environmental reservoirs to contribute to the spread of multidrug-resistant bacteria.
Area of Science:
- Microbiology
- Environmental Science
- Infectious Diseases
Background:
- Hospital sewage acts as a reservoir for antibiotic resistance genes.
- Multidrug-resistant (MDR) bacteria carrying New Delhi metallo-β-lactamase-1 (NDM-1) plasmids are a significant public health concern.
- Routine surveillance of hospital sewage has identified diverse MDR bacteria harboring NDM-1 plasmids.
Purpose of the Study:
- To report the isolation and characterization of a carbapenem-resistant Acinetobacter towneri strain harboring an NDM-1-positive plasmid from hospital sewage.
- To investigate the genetic features of the NDM-1 plasmid and its associated resistance mechanisms.
Main Methods:
- Bacterial isolation and identification using Vitek 2 compact system and 16S rRNA sequencing.
- Antimicrobial susceptibility testing (AST) and gene amplification/sequencing for blaNDM-1.
- Plasmid analysis via Southern blotting, pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing.
- Conjugation experiments to assess plasmid transferability.
Main Results:
- An MDR Acinetobacter towneri strain, AeBJ009, carrying an NDM-1-positive plasmid (pNDM-AeBJ009) was isolated from hospital sewage.
- The blaNDM-1 gene was located on a 47kb plasmid within a Tn125 element.
- Conjugation experiments to transfer the plasmid to Escherichia coli were unsuccessful.
- A single-nucleotide polymorphism was identified in the ble gene on pNDM-AeBJ009 compared to a known homologue.
Conclusions:
- The isolation of NDM-1-positive Acinetobacter towneri from hospital sewage underscores the potential for environmental reservoirs to harbor and disseminate carbapenem resistance.
- Enhanced monitoring and control of MDR pathogens in environmental settings are crucial for preventing the spread of nosocomial infections.
- The unique genetic features of the identified blaNDM-1 variant warrant further investigation.
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