Effective transfer of a 47 kb NDM-1-positive plasmid among Acinetobacter species
Tzu-Wen Huang1, Tsai-Ling Lauderdale2, Tsai-Lien Liao1
1Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan, Taiwan.
Objectives:
To investigate the link between two NDM-1-positive Acinetobacter isolates from the same hospital, the plasmid profiles of the isolates were examined. These two isolates were found from a surveillance programme within 3 months from two patients without obvious physical contact or hospitalization time overlap.
Methods:
Antimicrobial susceptibility tests, genome sequencing of both isolates and plasmid transfer experiments were performed. A comparative study of similar plasmids was performed using BLAST analysis.
Results:
The antimicrobial susceptibility of the isolates (Acinetobacter soli M131 and Acinetobacter pittii MS32) and their Escherichia coli transconjugants revealed a conjugative plasmid that carried the carbapenem resistance determinant. Eleven plasmids were observed in M131 and three in MS32. Each isolate shared an identical plasmid that carried the blaNDM-1 gene. This 47 271 bp plasmid harbours a conserved blaNDM-1-containing region that is flanked by ISAba125 and ISAba11 elements, and also contains a Ti-type conjugative operon. The plasmid is nearly identical in sequence to those of Acinetobacter isolates from China. In contrast to the mobilization of the blaNDM-1 sequence in Enterobacteriaceae, which is mainly by transposition, this plasmid moves as a whole among Acinetobacter species. Consistently, this plasmid was found to transfer effectively by in vitro conjugation to several Acinetobacter species.
Conclusions:
The clinical and laboratory findings suggest that Acinetobacter species may serve as a reservoir of this blaNDM-1 plasmid. Our study demonstrates the potential of applying genome sequencing to the surveillance of antimicrobial-resistant bacteria.
Insights
Acinetobacter species can act as a reservoir for the blaNDM-1 plasmid, which confers carbapenem resistance. Genome sequencing aids in tracking antimicrobial-resistant bacteria and understanding plasmid transmission dynamics.
Area of Science:
- Microbiology
- Genomics
- Antimicrobial Resistance
Background:
- The emergence of carbapenem-resistant Enterobacteriaceae (CRE) is a significant global health concern.
- Acinetobacter species are increasingly recognized as important multidrug-resistant pathogens.
- The New Delhi metallo-beta-lactamase 1 (NDM-1) enzyme confers resistance to a broad range of beta-lactam antibiotics, including carbapenems.
Purpose of the Study:
- To investigate the genetic link and plasmid profiles of two NDM-1-positive Acinetobacter isolates from the same hospital.
- To characterize the plasmid carrying the blaNDM-1 gene and its transmission mechanism.
- To assess the utility of whole-genome sequencing for antimicrobial resistance surveillance.
Main Methods:
- Antimicrobial susceptibility testing.
- Whole-genome sequencing of Acinetobacter isolates.
- Plasmid transfer experiments (conjugation).
- Comparative plasmid analysis using BLAST.
Main Results:
- Two Acinetobacter isolates, Acinetobacter soli M131 and Acinetobacter pittii MS32, shared an identical 47,271 bp conjugative plasmid carrying the blaNDM-1 gene.
- This plasmid harbors a conserved blaNDM-1 region flanked by ISAba125 and ISAba11 elements and a Ti-type conjugative operon.
- The plasmid sequence was nearly identical to those found in Acinetobacter isolates from China and transferred effectively to other Acinetobacter species in vitro.
Conclusions:
- Acinetobacter species can serve as a reservoir for the blaNDM-1-carrying plasmid.
- The blaNDM-1 plasmid is mobilized as a whole unit among Acinetobacter species, differing from its transpositional movement in Enterobacteriaceae.
- Whole-genome sequencing is a valuable tool for the surveillance of antimicrobial-resistant bacteria and plasmids.
