Molecular Mechanism of the β-Lactamase Mediated β-Lactam Antibiotic Resistance of Pseudomonas aeruginosa Isolated From a Chinese Teaching Hospital

Pseudomonas aeruginosa can cause infections in the blood, lungs (pneumonia), or other parts of the body after surgery. To investigate the molecular characteristics of β-lactam antibiotic resistance of P. aeruginosa isolated from a hospital population between 2015 and 2017, in this study, the antimicrobial susceptibility and the resistance gene profile of the bacteria were determined. The Pulsed-field gel electrophoresis (PFGE) was used to characterize the clonal relatedness and sequencing and comparative genomic analysis were performed to analyze the structure of the resistance gene-related sequences. As a result, of the 260 P. aeruginosa strains analyzed, the resistance rates for 6 β-lactam antibiotics ranged from 4.6 to 9.6%. A total of 7 genotypes of 44 β-lactamase genes were identified in 23 isolates (8.9%, 23/260). Four transconjugants from different donors carrying bla(CARB-3) exhibited a phenotype of reduced susceptibility to piperacillin–tazobactam, ceftazidime, and cefepime, and 2 transconjugants harboring bla(IMP-45) exhibited a phenotype of reduced susceptibility to carbapenems. bla(CARB) positive isolates (n = 12) presented six PFGE patterns, designated groups A to F. Two bla genes (bla(IMP-45) and bla(OXA-1)) in PA1609 related to a class 1 integron (intI1-bla(IMP-45-)bla(OXA-1)-aac(6′)-Ib7-catB3-qacE∆1-sul1) were encoded on a plasmid (pPA1609-475), while the bla(CARB-3) gene of PA1616 also related to a class 1 integron was located on the chromosome. The results suggest that β-lactam antibiotic resistance and clonal dissemination exist in this hospital population. It indicates the necessity for molecular surveillance in tracking β-lactamase-producing strains and emphasizes the need for epidemiological monitoring.