Genomic and phenotypic characterization of six multidrug-resistant Acinetobacter pittii isolates

Area of Science:

• Microbiology
• Infectious Diseases
• Genomics

Background:

• The Acinetobacter calcoaceticus-baumannii complex causes significant nosocomial infections.
• Acinetobacter baumannii is globally prevalent, but Acinetobacter pittii is an emerging pathogen within this complex.
• Clinical Acinetobacter pittii isolates remain undercharacterized.

Purpose of the Study:

• To investigate the genomic and phenotypic characteristics of clinical Acinetobacter pittii isolates.
• To assess the virulence and carbapenem resistance potential of Acinetobacter pittii.

Main Methods:

• Whole genome sequencing and phylogenetic analysis of six clinical Acinetobacter pittii isolates.
• Phenotypic characterization including antimicrobial resistance profiling, motility, and biofilm production.
• Plasmid transfer experiments and a Zophobas morio survival model to assess virulence.

Main Results:

• Isolates were genetically distinct and harbored OXA-type β-lactamase genes, conferring resistance to ceftazidime, ertapenem, and in one case, imipenem and meropenem.
• Plasmid-mediated transfer of bla_OXA-72 conferred carbapenem resistance to a recipient Acinetobacter baumannii strain.
• Acinetobacter pittii isolates demonstrated variable motility and biofilm production, with one carbapenem-resistant strain exhibiting high virulence in a Zophobas morio model.

Conclusions:

• Acinetobacter pittii acts as a reservoir for carbapenem resistance genes and can cause severe infections.
• Enhanced infection control measures for the Acinetobacter calcoaceticus-baumannii complex should explicitly include Acinetobacter pittii.