A study on the mechanism of the Carbapenems-tolerance in Pseudomona aeruginosa.

Objective To study the mechanism of the Carbapenems-tolerance in Pseudomona aeruginosa(P.aeruginosa). Method Thirty-one strains of P.aeruginosa isolated from November 2008 to April 2009 in our hospital were analyzed.According to the results of drug sensitivity test,the thirty-one strains of P.aeruginosa were divided into Carbapenems-tolerance group(21 strains) and Carbapenems-sensitive group(10 strains).Meanwhile,a standard strain of P.aeruginosa ATCC 27853 was also studied and an imipenem-EDTA inhibition test was conducted to detect metallo-beta-lactamases.PCR method was used to detect the oprD2 gene in P.aeruginosa,so as to study the mechanism of the Carbapenems-tolerance in P.aeruginosa.Result 7 of 21 strains of Carbapenems-tolerance P.aeruginosa produced metallo-beta-lactamases;15 of 21 strains of Carbapenems-tolerance P.aeruginosa were shown to be oprD2 gene negative,while the other 6 were positive.In contrast,all of the 10 strains of the Carbapenems-sensitive P.aeruginosa were found to be oprD2 gene positive,and so was the standard strain ATCC 27853.The results of the Chi-square test revealed that the difference between the positive rates of the oprD2 gene in the Carbapenems-tolerance and sensitive P.aeruginosa was statistically highly significant.Conclusion Loss of the oprD2 gene and metallo-beta-lactamases-producing ability were the important mechnisms of the Carbapenems-tolerance in P.aeruginosa of our hospital.