Resistant Genes and Cluster Analysis in Multidrug-resistant Pseudomonas aeruginosa

OBJECTIVE To investigate resistant genes encoding β-lactamases and aminoglycoside modifying enzymes in Pseudomonas aeruginosa isolated from clinical specimens,and phylogenetic analysis was performed.METHODS Antimicrobial susceptibility test was performed by PhoenixTM-100 system.Resistant genes encoding β-lactamases,aminoglycoside modifying enzymes and antiseptic resistance were detected by PCR amplification and verified by DNA sequencer.RESULTS The resistant rates of β-lactams including ampicillin/sulbactam,piperacillin,piperacillin/tazobactam,cefotaxime,ceftazidime,cefepime,imipenem and meropenem in 190 strains of P.aeruginosa were 98.9%,59.5%,45.8%,77.4%,34.2%,38.4%,15.3% and 6.8%,respectively.Ciprofloxacin and levofloxacin still showed powerful activities with resistance being 15.3% and 21.0%.The positive rates of blaVEB, blaGES and blaCARB genes were 9.5%,9.5% and 57.1% in 21 isolates.Twenty strains lost oprD2 genes.However,the β-lactamase genes of TEM,SHV,OXA,PER,IMP,VIM,SPM,GIM and DHA were not found.Three resistant genes encoding aminoglycoside-modifying enzymes were found in 21 isolates,such as aac(6′)-Ⅰ,aac(6′)-Ⅱ and ant(2″)-Ⅰ,and they accounted for 9.5%,61.9% and 66.7%,respectively.The positive rate of qacE△1-sul1 genes was 66.7% in 21 isolates.CONCLUSIONS P.aeruginosa isolated in clinic has carried many resistant genes.The loss of oprD2 gene may be the important cause of P.aeruginosa resistant to imipenem.Cluster analysis indicates that the spread of clones occurred in our hospital.