Clinical application and evaluation of rapid detection of carbapenem resistance genes in blood cultures by Xpert Carba-R / 中华检验医学杂志

ABSTRACT

This work aims to evaluate a rapid detection method of carbapenem resistance genes in blood cultures based on Xpert Carba-R and preliminarily evaluate its clinical application.Methods:Sixteen strains of Enterobacterales carrying different carbapenem resistance genes were selected to prepare simulated positive blood culture samples and Xpert Carba-R was used to directly detect carbapenem resistance genes in the simulated positive blood culture. From January 2022 to June, a prospective study was conducted on a total of 117 Enterobacteriaceae-positive blood culture samples in the First Affiliated Hospital of Nanjing Medical University. Xpert Carba-R, detecting five kinds of carbapenem resistance genes in these samples, was evaluated in sensitivity and specificity compared to polymerase chain reaction sequencing. Meanwhile clinical data of positive patients was collected for prognostic analysis. Results:Of the 16 simulated specimens, 14 strains had carbapenem resistance genes detected by Xpert Carba-R, including 8 bla KPC, 5 bla NDM and 1 bla IMP, showing 100% agreement with the known results. As of the 117 clinical specimens, 28 cases were determined to be Enterobacterales harboring carbapenem resistance genes, including 24 bla KPC, 2 bla NDM and 2 bla KPC+ bla NDM. In comparison to the PCR sequencing, the sensitivity and specificity of Xpert Carba-R were both 100% for blood culture samples, and furthermore, the detection time was significantly reduced. Of the 25 positive patients, 9 cases were treated with monotherapy and 5 cases were effective, other 16 cases received combined treatment and 12 cases were effective. A total of 17 cases were effective, 8 cases were ineffective and 3 of them died, the mortality rate was 12% (3/25). Conclusion:Xpert Carba-R can rapidly and accurately detect carbapenem resistance genes in blood culture, which can provide evidence for rational drug therapy in early clinical stage.