A Study On The Mechanism Of The Carbapenems-tolerance In Pseudomonas Aeruginosa

Objective:Pseudomonas Aeruginosa(PA) isolated in our hospital were analyzed, to study the mechanism of the Carbapenems-tolerance in it, to guide rational clinical use of drugs and the development of new medicines, prevent or delay the emergence and spread of drug resistant strains.Methods:Thirty-one strains of PA isolated from November 2008 to April 2009 in our hospital were analyzed. Acording to the results of drug sensitivity test, the thirty-one strains of PA were divided into Carbapenems-tolerance group(21 strainas) and Carbapenems-sensitive group(10 strains). Meanwhile, a standard quality control strain of PA ATCC27853 was also studied, one imipenem-EDTA inhibinted test was taken to detect metallo-beta-lactamases, and PCR method was used to detect the oprD2 gene in PA, to study the mechanism of the Carbapenems-tolerance in Pseudomonas Aeruginosa, SPSS 13.0 software is applicationed for Fisher exact test, to analysis the results of the PCR, and Compare the ddifference between the positive rates of the oprD2 gene in the Carbapenems-tolerance and sensitive PA, P<0.05 was statistically significant.Result:1.7 of 21 strains of Carbapenems-tolerance PA were shown to be positive for the metallo-beta-lactamases; the remaining 14 strains, the quality control strain and all of the 10 strains of the Carbapenems-sensitive were shown to be negative for the metallo-beta-lactamases;2. Template DNA of the quality control strain ATCC27853 is amplified with Primers of oprD2, express a purpose gene fragment of 193bp, based on this standard strain as a positive control, pure water as a negative control,15 of 21 strains of Carbapenems-tolerance PA were shown to be negative for the oprD2gene, while 6 of them were positive.In contrast, all of the 10 strains of the Carbapenems-sensitive PA were found to be positive for the oprD2 gene, and so was the standard strain ATCC27853. The results of the statistical tes revealed that the difference between the positive rates of the oprD2 gene in the Carbapenems-tolerance and sensitive PA was statistically highly significant (P<0.01).Conclusion:1.There were the resistance mechnisms of oprD2 gene deletion and metallo-beta-lactamases-producing in the carbapenem resistant Pseudomonas aeruginosa isolated in our hospital, and the phenomenon of oprD2 gene deletion is serious, with Should be highly valued in clinical practice.2. There are other resistance mechanisms in the carbapenem resistant Pseudomonas aeruginosa isolated in our hospital in addition to oprD2 gene deletion and metallo-beta-lactamases-producing.