PAU-1, a Novel Plasmid-Encoded Ambler Class A β-Lactamase Identified in a Clinical Pseudomonas aeruginosa Isolate

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 aeruginosa 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 tnpA-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.