PER-8, a Novel Extended-Spectrum β-Lactamase PER Variant, from an Acinetobacter baumannii Clinical Isolate in Nepal

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• Extended-spectrum beta-lactamases (ESBLs) are a significant cause of antibiotic resistance in Gram-negative bacteria.
• Acinetobacter baumannii is an opportunistic pathogen frequently associated with hospital-acquired infections and multidrug resistance.
• The PER-type ESBLs are a class of beta-lactamases that confer resistance to a broad range of beta-lactam antibiotics.

Purpose of the Study:

• To identify and characterize a novel PER-type extended-spectrum beta-lactamase (ESBL) from a clinical isolate of Acinetobacter baumannii.
• To investigate the biochemical properties and substrate specificity of the newly identified PER-8 enzyme.
• To analyze the genetic context and plasmid-mediated dissemination potential of the blaPER-8 gene.

Main Methods:

• Isolation and identification of Acinetobacter baumannii from a clinical sample.
• Molecular characterization of the novel beta-lactamase gene (blaPER-8) using sequencing.
• Biochemical assays to determine kinetic parameters (kcat/K) for various beta-lactam substrates, including aztreonam and imipenem.
• Analysis of the surrounding genetic elements and plasmid structure harboring the blaPER-8 gene.

Main Results:

• A novel PER-type ESBL, designated PER-8, was identified in an Acinetobacter baumannii clinical isolate from Nepal.
• PER-8 differs from PER-7 by a single amino acid substitution (Glycine to Glutamic acid at position 39).
• PER-8 exhibited reduced catalytic efficiency (kcat/K) against aztreonam but increased efficiency against imipenem compared to PER-7.
• The blaPER-8 gene was located within a complex genetic structure (intI1 blaPSE-1 qacEDI sulI ISCR1-blaPER-8 gts sulI orfX) on a 100-kb plasmid.

Conclusions:

• The identification of PER-8 highlights the ongoing evolution of ESBLs in Acinetobacter baumannii.
• The altered substrate profile of PER-8 may impact treatment strategies for infections caused by resistant strains.
• The plasmid-borne nature and complex genetic environment of blaPER-8 suggest potential for horizontal gene transfer and spread.