Detection of the relevant resistant genes in Imipenem-resistant Pseudomonas aeruginosa

Objective To survey the relevant resistant genes in imipenem-resistant Pseudomonas aeruginosa.Method Two hundred and twenty strains of P.aeruginosa were isolated from hospitalized patients′ samples between 2003 and 2009.Three-dimensional test was used to screen P.aeruginosa which produce β-lactamases.PCR and multiplex PCR were performed to detect Carbapenemase genes and plasmid-mediated AmpC β-lactamase genes respectively.The expression of the oprD2 genes in P.aeruginosa were analyzed with Real-time reverse transcriptase PCR.Result 43 strains producing β-lactamases were isolated;the constitution ratio of AmpC β-lactamases,extended spectrum β-lactamases(ESBLs),metallo-β-lactamases(MBLs) and unknown type of β-lactamases were 58.14%(25/43),18.60%(8/43),4.65%(2/43) and 16.28%(7/43),respectively.Among the 74 strains of Imipenem-resistant P.aeruginosa,two strains carried IMP-9 gene;the plasmid-mediated AmpC β-lactamase gene DHA was identified in one strain.The other carbapenemase gene detection saw negative results.40 strains showed decreasing expression of oprD2 gene while that of other 34 strains showed normal expression rate.Conclusion The diminished production of oprD2 gene is the major cause of imipenem resistence in P.aeruginosa.AmpC β-lactamases can hydrolyze imipenem feebly,which may has some relation with imipenem resistance.