Abstract：Objective: To explore the mechanisms of the heterogeneous drug resistance against imipenem in Pseudomonas aeruginosa(P．aeruginosa) isolated from clinical specimens. Methods: The sensitivity of 310 strains of P.aeruginosa to imipenem(IMP) was evaluated with conventional KB method and the instrument method . The metal βlactamase phenotype was analyzed with double disc inhibitory synergy test. The expression level of efflux pump gene in bacteria was detected with reverse transcription realtime quantitative PCR. The biofilm formation was evaluated with semiquantitative analysis of crystal violet. Furthermore, drugresistant genes of bacteria OPRD2 was detected with PCR. Results: There were 244 IMP sensitive strains and 66 insensitive strains in the 310 clinically isolated P．aeruginosa, and 36 strains had heteroresistance to IMP among 244 IMP sensitive strains. The total ratio of strains of P.aeruginosa with heteroresistance to IMP was 11.6%. Among the 36 heteroresistance P.aeruginosa, none produced metal βlactamase, and they all expressed high level in MexAB efflux pump and had high level biofilm formation. There were 6 strains showed OPRD2 gene deletion. Conclusion: There are many strains of P.aeruginosa with heterogeneous drug resistance against IMP in clinical samples. The mechanism of the heterogeneous drug resistance against IMP may be related to high level MexAB efflux pump, high level biofilm formation and resistant genes.
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2018, Vol. 28 
