Diagnostic performance of the Xpert Carba-R assay for active surveillance of rectal carbapenemase-producing organisms in intensive care unit patients

Abstract

Background There are growing concerns regarding the spread of carbapenemase-producing organisms (CPOs) among patients in long-term care facilities (LTCFs) and hospitals in South Korea. We have established a screening protocol for the detection of CPOs in high-risk patients upon admission to intensive care units (ICUs). The diagnostic performance of the Xpert Carba-R assay was compared to that of rectal culture for CPO detection in high-risk patients upon ICU admission. Methods A total of 408 consecutive rectal swabs were obtained from December 2016 to December 2017. CPO screening was performed using the Xpert Carba-R assay (Cepheid, Sunnyvale, CA, USA). When a carbapenemase gene was detected, additional rectal swabs were incubated overnight and inoculated on chromID CARBA medium (bioMérieux, Marcy l’Etoile, France). Bacterial carbapenemase genes, including bla KPC , bla NDM , bla VIM , bla IMP-1 , and bla OXA-48 , were confirmed by conventional PCR. The diagnostic performance of the Carba-R assay was ascertained based on the culture results. Results The prevalence of CPO carriage was 7.4% according to the Carba-R assay and 3.7% according to rectal culture. The median Ct values of IMP-1 and KPC were significantly different (35.2 vs. 26.6, P = 0.0143). The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the Carba-R assay were 100.0% (95% confidence interval [CI], 78.2–100.0), 96.7% (94.4–98.2), 53.6% (40.4–66.4) and 100.0% (99.0–100.0), respectively. Conclusions We demonstrated the prevalence of CPO carriage in high-risk patients upon ICU admission and evaluated the diagnostic performance of the Carba-R assay. The combined use of the Xpert Carba-R assay and culture produces rapid and reliable results for the active surveillance of rectal CPO in ICU patients.

Parallel Validation of the NG-Test Carba 5 and the Xpert Carba-R for Detection and Characterization of Carbapenem-Resistant Enterobacterales Causing Bloodstream Infections

“…Ten microliters of Liu et al 2 jmdjournal.org -The Journal of Molecular Diagnostics the bacterial suspension was added into 5 mL of sample reagent and vortexed vigorously for 10 seconds, then 1.7 mL of the sample reagent was loaded into an Xpert Carba-R cartridge and placed into the GeneXpert instrument. 17 For the detection of the carbapenemase genes in positive BCB specimens, 10 mL of BCB specimen was added into 5 mL of sample reagent. The mixture was vortexed vigorously for 10 seconds and 1.7 mL of sample was loaded for detection as described in the previous paragraph.…”

Comparison of the Clinical Outcomes of Patients With Positive Xpert Carba-R Tests for Carbapenemase-Producing Enterobacterales According to Culture Positivity

“…First, as we performed the Xpert Carba-R assay only once, the number of patients with positive PCR results could have been underestimated. However, several studies have evaluated the performance of the Xpert Carba-R assay [ 7–9 , 16 , 22 ] and report its sensitivity and specificity as 100% and 96.7%, respectively [ 8 ]. Second, false-negative results of culture using ChromID CARBA agar due to weak hydrolysis by metallo-β-lactamase carbapenemase [ 8 ] and low sensitivity for OXA-48–like producers cannot be excluded as we did not perform further direct PCR sequencing of carbapenemase genes in patients with negative culture results.…”

“…However, several studies have evaluated the performance of the Xpert Carba-R assay [ 7–9 , 16 , 22 ] and report its sensitivity and specificity as 100% and 96.7%, respectively [ 8 ]. Second, false-negative results of culture using ChromID CARBA agar due to weak hydrolysis by metallo-β-lactamase carbapenemase [ 8 ] and low sensitivity for OXA-48–like producers cannot be excluded as we did not perform further direct PCR sequencing of carbapenemase genes in patients with negative culture results. Third, as we defined transmission as the presence of identical genotypes in index and exposed patients, and we did not perform preadmission testing in all departments, exposed patients with identical CPE genotypes might have acquired CPE from other sources.…”

Detection of Multidrug-Resistant Enterobacterales—From ESBLs to Carbapenemases

“…The predecessor Check-MDR CT103 performed well in the study by Cuzon et al, with sensitivity and specificity of 95–100% and 100%, respectively [ 84 ]. Other tests for CPE detection from rectal swabs include the Xpert Carba-R assay for the GeneXpert system (Cepheid, Sunnyvale, California [ 139 , 140 , 141 ]), the CRE ELITe MGB Kit (ELITechGroup, Puteaux, France [ 85 ]), GenePOC/Revogene Carba C assay (Meridian Bioscience, Cincinnati, Ohio [ 46 ]), and assays developed by MOBIDIAG for the Amplidiag ® Easy system, namely, Amplidiag CarbaR + VRE and Amplidiag CarbaR-MCR assays (Mobidiag Ltd., Espoo, Finland [ 86 , 87 ]).…”