Relationship between antimicrobial susceptibility and highly active β-lactamases in Pseudomonas aeruginosa

  Objective   To investigate the antimicrobial resistance and the prevanlence of production of AmpC β-lactamases, extended-spectrum β-lactamases(ESBLs)and metallo β-lactamases(MBLs)in Pseudomonas aeruginosa(P.aeruginosa) clinical isolates, for guiding the rational use of antibiotics.

  Methods   Antimicrobial susceptibility tests were done by Kirby-Bauer disk diffusions method, the pheno types of P.aeruginosa strains harboring AmpC β-lactamases and/or ESBLs were detected by modified three-dimensional extracttest, while MBLs were identified using MBLE-teststrips.

  Results   The suscep- tibility rate of 186 P.aeruginosa clinical isolates to imipenem was the highestabout82.3%, as to ciprofloxacin, piperacillin/tazobactam, ceftazidime, amikacin, cefoperazone/sulbactam were 75.3%, 74.2%, 72.6%, 71.0%, 70.4% respectively, but to ticarcillin, cefoperazone, aztreonam were no more than 60%.The resistantrates to cefotaxime and ceftriaxone were 61.8% and 55.9% respectively.AmpC -lactamases, Amcp β-lactamases combined with ESBLs, ESBLs and MBLs producing strains were detected in 8.6%, 2.7%, 14.5% and 4.8% of P.aeruginosa respectively.

  Conclusion   The resistantphenomenon of P.aeruginosa clinical isolates should not be ignored, production of highly active β-lactamases is one of resistantmechanisms in P.aeruginosa, imipenem is still the bestchoice for treating infection caused by P.aeruginosa.