Evaluation of the BYG Carba Test, a New Electrochemical Assay for Rapid Laboratory Detection of Carbapenemase-Producing Enterobacteriaceae

Abstract

Accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) constitutes a major laboratory diagnostic challenge. We evaluated an electrochemical technique (the BYG Carba test) which allows detection of CPE in less than 35 min. The BYG Carba test was first validated in triplicate against 57 collection isolates with previously characterized β-lactam resistance mechanisms (OXA-48, n = 12; KPC, n = 8; NDM, n = 8; VIM, n = 8; IMP, n = 3; GIM, n = 1; GES-6, n = 1; no carbapenemase, n = 16) and against a panel of 10 isolates obtained from the United Kingdom National External Quality Assessment Service (NEQAS). The test was then evaluated prospectively against 324 isolates referred to the national reference center for suspicion of CPE. The BYG Carba test results were compared with those obtained with the Carba NP test using multiplex PCR sequencing as the gold standard. Of the 57 collection and the 10 NEQAS isolates, all but one GES-6-producing isolate were correctly identified by the Carba BYG test. Among the 324 consecutive Enterobacteriaceae isolates tested prospectively, 146 were confirmed as noncarbapenemase producers by PCR while 178 harbored a carbapenemase gene (OXA-48, n = 117; KPC, n = 25; NDM, n = 23; and VIM, n = 13). Prospectively, in comparison with PCR results, the BYG Carba test displayed 95% sensitivity and 100% specificity versus 89% and 100%, respectively, for the Carba NP test. The BYG Carba test is a novel, rapid, and efficient assay based on an electro-active polymer biosensing technology discriminating between CPE and non-CPE. The precise electrochemical signal (electrochemical impedance variations) allows the establishment of real-time objective measurement and interpretation criteria which should facilitate the accreditation process of this technology.

Comparative Evaluation of Four Phenotypic Tests for Detection of Carbapenemase-Producing Gram-Negative Bacteria

“…The ␤ Carba test (BCT) is based on the opposite color shift from yellow to orange, red, or purple of an undisclosed chromogenic carbapenem substrate in the presence of carbapenem-hydrolyzing enzymes. The BYG Carba test (BYG) is an electrochemical assay that detects the increase of conductivity of a polyaniline-coated electrode, which is highly sensitive to modification of pH and of redox activity occurring during the imipenem enzymatic hydrolysis reaction (7).…”

“…Several phenotypic assays developed to detect carbapenemase production from bacterial culture within hours are now commercially available, including the Neo-Rapid Carb kit (NRCK) (Rosco Diagnostica A/S, Taastrup, Denmark), the Rapidec Carba NP test (RCNP) (bioMérieux SA, Marcy l'Etoile, France), and the recently marketed ␤ Carba test (BCT) (Bio-Rad Laboratories N.V., Marnes-la-Coquette, France). In addition, we recently developed and validated the BYG Carba test (BYG), an in-house rapid electrochemical assay which allows objective detection (positivity based on a cutoff value) of carbapenemase-producing Enterobacteriaceae (CPE) from bacterial culture colonies in less than 30 min (7).…”

Clinical and laboratory considerations for the rapid detection of carbapenem-resistant Enterobacteriaceae

“…8/117 (6.8%) OXA-48-like carbapenemase producers were negative by this test, as was 1/13 VIM-2 isolates (7.7%) evaluated. 36 Several groups have adapted matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI TOF MS), a tool used by many clinical laboratories for the identification of bacteria and fungi, to the detection of carbapenemase activity. These methods rely on incubation of the organism in question with a carbapenem, typically for 2-4 hours, and the massbased detection of the carbapenem and its degradation productions.…”

Chromosomal Amplification of the bla OXA-58 Carbapenemase Gene in a Proteus mirabilis Clinical Isolate

“…Detection of carbapenemase-producing P. mirabilis isolates may be difficult based only on antibiotic susceptibility testing, since this species naturally displays reduced susceptibility to imipenem. Nevertheless, we have detected significant carbapenemase activity in P. mirabilis 1091 by two different biochemical tests: CARBA-NP and the recently described BYG test (16,17) (data not shown). However, PCR failed to detect acquired carbapenemase genes commonly found in Enterobacteriaceae (data not shown).…”

“…MICs were determined as recommended by the EUCAST using the Etest technique (bioMérieux, Marcy l'Etoile, France). The carbapenemase activity was assessed using the updated Carba NP test and the BYG test on colonies recovered from MH agar medium supplemented with ZnSO 4 as previously described (16,17).…”