plasmid-mediated AmpC β-lactamase (MIR-1) in a strain of Cray Borrelia bacterium isolated from a patient in Rhode Island

The aim of the present study was to investigate the resistance of plasmid-mediated AmpC β-lactamase in Pseudomonas aeruginosa, to detect and identify the AmpC genotype and to provide evidence for antibiotic applications in the clinic. Resistance phenotype in 108 strains of clinically isolated P. aeruginosa was determined by Kirby-Bauer disk test and cefoxitin three dimensional test in AmpC-positive strains. Plasmids were extracted from AmpC-positive strains using the SDS-alkali splitting technique. The depurated plasmid was used to amplify AmpC β-lactamase genes by PCR. Positive PCR products were sequenced by the Shanghai Sangon Biological Engineering Technology Company. Gene homology of PCR products with other index sample gene sequences was compared. In the present study, 28 AmpC enzyme-positive P. aeruginosa strains among 108 were identified. Multidrug‐resistance to antibiotics was observed in positive AmpC P. aeruginosa strains and a new P. aeruginosa strain of plasmid-mediated CMY-7 type AmpC enzyme was identified. In addition, AmpC type β-lactamases were revealed to be important in the resistance mechanism to antibiotics in P. aeruginosa. This is the first report of CMY‐7 plasmid‐mediated AmpC enzyme expression in P. aeruginosa.