Purpose: The aim of this work was to identify a novel β-lactamase gene bla _PAU-1 encoded on the plasmid of a clinical Pseudomonas aeru ginosa isolate.
Materials and methods: The clinical P. aeruginosa  isolates were isolated from a hospital in southern China. Molecular cloning was performed to analyze the function of the resistance gene. The minimum inhibitory concentration (MIC) was determined by means of the agar dilution method to determine the antimicrobial susceptibilities of the strains. Whole-genome sequencing and comparative genomics analysis were performed to analyze the structures of the resistance gene-related sequences.
Results: PAU-1 is a molecular class A, Bush-Jacoby group 2be enzyme which encoded 293 amino acids and shared 74% amino acid identity with a putative class A β-lactamase from Rhodoferax saidenbachensis . Cloned bla _PAU-1 in Escherichia coli  and P. aeruginosa  conferred resistance to piperacillin and ampicillin, and elevated the MIC with a 2–3 dilution for some oxyimino-β-lactams in P. aeruginosa . The genetic environment of bla _PAU-1 is tnp A-res-hp-relE-bla _PAU-1-lysR , which is in accordance with the structure of a Tn3  transposon. Epidemiological investigation of bla _PAU-1 in the same district did not show any evidences of molecular dissemination associated with this determinant.
Conclusion: A novel class A β-lactamase gene, bla _PAU-1, associated with the mobile genetic element was identified on a transferable plasmid in a clinical P. aeruginosa  isolate. Strict surveillance for the emergence of the new determinant should be established and an effort should be made to block the dissemination of this determinant.
Keywords: Pseudomonas aeruginosa , antimicrobial resistance, β-lactamase, PAU-1