Uncommon carbapenemase-encoding plasmids in the clinically emergent Acinetobacter pittii

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Carbapenem resistance is a significant threat in healthcare settings.
• Acinetobacter species are important opportunistic pathogens.
• Carbapenemase-carrying plasmids contribute to antimicrobial resistance spread.

Purpose of the Study:

• Characterize two carbapenemase-carrying plasmids (pLS488 and pLS535) from Acinetobacter pittii.
• Investigate the transferability of these plasmids to Acinetobacter baumannii.

Main Methods:

• Antimicrobial susceptibility testing and carbapenemase detection (Blue-Carba).
• PCR sequencing for carbapenem-hydrolysing class D β-lactamase (CHDL) genes.
• Pulsed-field gel electrophoresis (PFGE), hybridization, and whole-genome sequencing (WGS).
• Plasmid transfer via conjugation and electroporation.

Main Results:

• pLS488 is a novel conjugative plasmid carrying blaOXA-23 in A. pittii, potentially aiding OXA-23 spread.
• pLS535, belonging to the GR7 incompatibility group, carries blaOXA-58 and is transferable to A. baumannii via electroporation.
• Identified the first CHDL-carrying A. pittii isolates in Portugal.

Conclusions:

• Acinetobacter pittii acts as a reservoir for carbapenemase genes.
• These plasmids can disseminate resistance genes to other bacterial species, including A. baumannii.
• Highlights the role of A. pittii clones in the spread of antimicrobial resistance.