Comparison of the NG-Test Carba 5, Colloidal Gold Immunoassay (CGI) Test, and Xpert Carba-R for the Rapid Detection of Carbapenemases in Carbapenemase-Producing Organisms

Abstract

Carbapenem-resistant Enterobacterales (CRE) are increasingly recognized as an urgent public health concern. The rapid and accurate identification of carbapenemases could provide insights into antimicrobial therapy and infection control. In this study, we evaluated the efficacy of three different methods, including the NG-test Carba 5, colloidal gold immunoassay (CGI) test, and Xpert Carba-R assay, for the rapid detection of five carbapenemases (KPC, NDM, IMP, OXA-48, and VIM). A total of 207 Gram-negative strains collected from patients and hospital sewages were tested. The presence or absence of carbapenemase genes in the whole-genome sequences was used as the gold standard for evaluating the accuracy of the above-mentioned three methods. Among the 192 strains carrying only one carbapenemase gene, the accuracies of the NG-Test Carba 5, CGI test, and Xpert Carba-R were 96.88% (95% CI, 93.01–98.72%), 96.88% (95% CI, 93.01–98.72%), and 97.92% (95% CI, 94.41–99.33%), respectively. Xpert Carba-R was able to detect all 13 types of KPC variants, including KPC-2, KPC-3, KPC-25, KPC-33, KPC-35, KPC-51, KPC-52, KPC-71, KPC-76, KPC-77, KPC-78, KPC-93, and KPC-123, with a detection sensitivity of 100.00% (95% CI, 96.50–100.00%), a specificity of 100.00% (95% CI, 92.38–100.00%), and a κ index of 1.00. For IMP, Carba 5 was superior to the other two methods, with a sensitivity of 100% (95% CI, 71.66–100.00%), a specificity of 100% (95% CI, 97.38–100.00%), and a κ index of 1.00. For the remaining 15 strains carrying two or three kinds of carbapenemase genes, Carba 5 performed the best, which accurately identified all the target genes, followed by Xpert Carba-R (12/15, 80.00%) and the CGI test (10/15, 66.67%). Therefore, all three assays demonstrated reliable performances in carbapenemase detection, and Xpert Carba-R should be recommended for the detection of KPC variants, especially for patients at a high risk of infections caused by ceftazidime/avibactam-resistant strains. IMPORTANCE: CRE was listed as one of the top three pathogens that are in critical need of new antibiotics by the WHO. The rapid and accurate identification of carbapenemases is important for antimicrobial therapy and infection control. In recent years, new beta-lactam/beta-lactamase inhibitor combinations such as ceftazidime/avibactam (CZA) have been approved by the Food and Drug Administration (FDA) to cope with CRE challenges. CZA was effective against class A, class C, and some class D enzymes such as OXA-48-like. However, CZA-resistant KPC variants emerged at an alarming speed, which posed a new challenge for the accurate identification of KPC variants. In this study, we evaluated the performance of two lateral flow immunochromatographic assays, namely, NG-test Carba 5 and the CGI test, and the automated real-time quantitative PCR Xpert Carba-R in the rapid detection of carbapenemases. Notably, 13 types of KPC variants were enrolled in this study, which covered most KPC variants discovered in China. Carba-R was superior to NG-teat Carba 5 and the CGI test; it was able to detect all of the included KPC variants, including KPC-2, KPC-3, KPC-25, KPC-33, KPC-35, KPC-51, KPC-52, KPC-71, KPC-76, KPC-77, KPC-78, KPC-93, and KPC-123.

The carbapenem inoculum effect provides insight into the molecular mechanisms underlying carbapenem resistance inEnterobacterales

“…We propose that this ertapenem to meropenem MIC ratio might therefore be better suited than either MIC alone to inform downstream testing and prioritize isolates for molecular or enzymatic carbapenemase detection (19,72,73). Recognizing that MIC thresholds for susceptibility may miss carbapenemase-producing isolates, EUCAST recommends a 16-fold lower MIC threshold for carbapenemase screening than their clinical susceptibility breakpoint (26).…”

“…5). While carbapenemase detection is performed with molecular or enzymatic testing in some laboratories (17,56,57), this fully phenotypic trait could be used to prioritize deployment of these advanced tests. Our work could extend recent advances showing that molecular detection of carbapenemases can accelerate the administration of targeted therapies, such as β-lactamase inhibitor combinations (58), and decrease mortality (19).…”

“…Determining resistance mechanisms could lead to better infection control measures, such as patient isolation to prevent further CP-CRE spread in hospitals (4,11,16). Some laboratories have started to test for resistance mechanisms in CRE (17)(18)(19), but this can be burdensome due to additional time, equipment, and expertise required. Capitalizing on existing antimicrobial susceptibility testing (AST) workflows to predict mechanisms of resistance would represent a clinical advance in the diagnosis of these critically important pathogens.…”

Clinical Characteristics and Associated Factors for Mortality in Patients with Carbapenem-Resistant Enterobacteriaceae Bloodstream Infection

“…Further studies are required to confirm this conclusion including whole-genome sequencing of the CPE strains to determine the clonality. Furthermore, various diagnostic methods are being investigated for the rapid diagnosis of multidrug-resistant organisms, which plays an important role in preventing transmission [ 22 , 23 , 24 , 25 ].…”

Fecal carriage and genetic characteristics of carbapenem-resistant enterobacterales among adults from four provinces of China

“…Only one suspected colony was analyzed per sample. Colonies were screened for the presence of five common carbapenemase genes ( bla KPC , bla NDM , bla OXA−48−like , bla IMP , and bla VIM ) using the NG-Test Carba5 assay (NG Biotech, Guipry, France) as previously described ( 21 ). According to the manufacturer's instructions, a colony of a pure cultivated strain was mixed with five drops of lysis buffer.…”