Production of AmpC β-lactamases and ESBLs by Pseudomonas aeruginosa isolated from lower respiratory tract

ObjectiveTo investigate the resistance,resistant phenotypes and prevalence of AmpC β-lactamases and extended spectrum β-lactamases(ESBLs) in Pseudomonas aeruginosa isolated from lower respiratory tract and guide rational use of antibacterial agents.MethodsA total of 520 P.aeruginosa isolates were collected from July 2003 to July 2004.Twenty multi-drug resistant P.aeruginosa strains were sieved after identification and susceptibility testing by Vitek AutoMicrobic System.AmpC β-lactamases and ESBLs were detected by three-dimensional test.AmpC β-lactamases genotypes were analyzed by PCR amplification and product sequencing.ResultsTobramycin,piperacillin-tazobactam and imipenem had good activity against P.aeruginosa.Three-dimensional test showed that AmpC β-lactamases were detected in 2 of the 20 isolates and neither AmpC β-lactamases nor extended spectrum β-lactamases(ESBLs) were found in the other 18 isolates.PCR amplification and DNA sequencing showed that DHA-1 β-lactamase was detected in one strain.AmpC fragment could not be amplified with the ampC primers in this test.ConclusionsAttention must be paid to the detection of AmpC β-lactamases,ESBLs in P.aeruginosa which may cause lower respiratory tract infections.Carbapenems,piperacillin-tazobactam,or ceftazidime combined with an aminoglycoside or ciprofloxacin can provide effective therapy for such infections.