Mechanism of imipenem induced ceftazidime resistance to pseudomonas aeruginosa

Objective: To investigate the incidence of imipenem induced ceftazidime resistance to pseudomonas aeruginosa(Pa),the expression of βlactamase code gene and outer membrane channel protein OprD2 gene,and the relationship between inhibitor of efflux pump and the sensitivity of imipenem and ceftazidime.Methods:325 strains of Pa were collected and isolated from 5 regional hospitals.116 imipenem induced ceftazidime-resistance to Pa strains were isolated by D test.The sensitivity of 14 antibiotics including imipenem was tested by disc diffusion method.IMP,VIM,SPM,GIM genes and outer membrane channel protein OprD2 gene were tested by PCR.The MIC value of Pa to imipenem and ceftazidime were tested before and after efflux pump inhibitor CCCP was added.Results:Among the 325 strains of Pa,35.7%(116/325) showed imipenem induced ceftazidime resistance.The sensitivity to imipenem and ceftazidime had no change before and after CCCP was added.Among the 116 strains of Pa,80.2%(93/116) were resistant to imipenem while sensitive to ceftazidime,and no IMP,VIM,SPM,GIM genes were detected,with 87.1%(81/93) had gene deletion of the outer membrane channel protein OprD2.Conclusion: Pa can induce imipenem causing ceftazidime resistance with no other mechanisms involved.Disappearing of outer membrane channel protein OprD2 gene is an important mechanism of imipenem resistance in this area.