Detection Of Carbapenemase-producing Enterobacteriaceae Research Articles

Nosocomial Outbreak Caused by NDM-5 and OXA-181 Carbapenemase Co-producing Escherichia coli.

Carbapenemase-producing Enterobacteriaceae (CPE) is an important and increasing threat to global health. From July to September 2017, 20 inpatients at a tertiary care hospital in Korea were either colonized or infected with carbapenem-resistant Escherichia coli strains. All of E. coli isolates co-produced blaNDM-5 and blaOXA-181 carbapenemase genes and shared ≥88% clonal relatedness on the basis of a cladistic calculation of the distribution of pulsed-field gel electrophoresis patterns. Rapid detection of CPE is one of the most important factors to prevent CPE dissemination because it takes long time for CPE to become negative.

Prospective evaluation of a screening algorithm for carbapenemase-producing Enterobacteriaceae.

Carbapenemase-producing Enterobacteriaceae (CPE) have become a major public health issue. The objective of the present study was to prospectively assess the analytical performance of a CPE detection algorithm based on phenotypic tests (the screening test) and MALDI-ToF hydrolysis (the confirmatory test). Over a 6-month period and based on a disk diffusion method, 74 carbapenem-resistant strains were included in this study. Of the collected isolates, 54 turned out to be negative after phenotypic tests. Hence, 20 strains (including all of the CPEs) were checked with the confirmation test. Seven strains were positive. After molecular biology assessments in a reference center, three of the seven were found to be false positives. The algorithm had a negative predictive value and a sensitivity of 100%, a specificity of 77%, and a positive predictive value of 20%. The algorithm has a 24-hour turnaround time and helps to avoid using expensive molecular biology tests; we consider that it can be used on a routine basis for screening clinical strains.

Establishment of a dual-wavelength spectrophotometric method for analysing and detecting carbapenemase-producing Enterobacteriaceae

The spread of carbapenemase-producing Enterobacteriaceae (CPE) is an increasing global public health concern. The development of simple and reliable methods for CPE detection is required in the clinical setting. This study aimed to establish a dual-wavelength measurement method using an ultraviolet–visible spectrophotometer to rapidly quantify imipenem hydrolysis in bacterial cell suspensions. The hydrolytic activities of 148 strains including various CPE strains (Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Enterobacter aerogenes containing the blaIMP, blaKPC, blaNDM, blaOXA, and blaVIM genes) were measured and analysed. A cut-off value was obtained for differentiation between CPE and non-CPE strains, and the method had high sensitivity (100%) and specificity (100%) within 60 min. Our system has potential clinical applications in detecting CPE.

Rapid detection of NDM, KPC and OXA-48 carbapenemases directly from positive blood cultures using a new multiplex immunochromatographic assay.

Bloodstream infections caused by carbapenemase-producing Enterobacteriaceae (CPE) are associated with treatment failure and increased mortality. Detection of CPE from blood cultures (BC) by standard methods takes 16–72 hours, which can delay the initiation of appropriate antimicrobial therapy and compromise patient outcome. In the present study, we developed and evaluated a new method for the rapid detection of carbapenemases directly from positive BC using a new multiplex immunochromatographic test (ICT). The new ICT was assessed using 170 molecularly characterized Enterobacteriaceae clinical isolates including 126 CPE (OXA-48-like (N = 79), KPC (N = 18) and NDM (N = 29)). After spiking with bacteria and incubation in a BC system, blood from positive BC bottles was hemolyzed, bacteria concentrated by centrifugation and lysed. The lysate was transferred to the RESIST-3 O.K.N. ICT (Coris BioConcept, Gembloux, Belgium), which detects OXA-48-like, KPC and NDM carbapenemases. The final results of the ICT were read when they became positive, at the latest after 15 min. All CPE isolates (126/126) were correctly detected with the new protocol (100% sensitivity, 100% specificity). There was perfect concordance between ICT results and molecular characterization. Total time to result was 20–45 min.Conclusions: This proof-of-principle study demonstrates that with the newly developed method, OXA-48-like, KPC and NDM carbapenemases can be reliably detected directly from positive BC bottles. The new method is more rapid than other currently available assays and can be performed in any routine microbiology laboratory. This can help to rapidly identify patients with CPE BSI and optimize the management of patients with these difficult-to-treat infections. Further studies are needed to assess the performance of the ICT in routine diagnostics.

Within-a-Day Detection and Rapid Characterization of Carbapenemase by Use of a New Carbapenem Inactivation Method-Based Test, CIMplus

The dissemination of carbapenemase-producing Enterobacteriaceae (CPE) is a major threat to public health. Rapid and accurate detection of CPE is essential for initiating appropriate antimicrobial treatment and establishing infection control measures. The carbapenem inactivation method (CIM), which has good sensitivity and specificity but a detection time of 20 h, was recently described. In this study, we evaluated the performances of a new version, the CIMplus test, which allows detection of carbapenemases in 8 h and characterization of carbapenemase classes, according to the Ambler classification, in 20 h. A panel of 110 carbapenem-resistant Enterobacteriaceae strains, including 92 CPE strains (with NDM, VIM, IMP, KPC, GES, OXA-48, and OXA-48-like enzymes), was used to evaluate test performance. Carbapenemase activity was detected at 8 h and 20 h. Characterization of carbapenemase classes, using specific inhibitors, was possible in 20 h. The CIMplus test had sensitivities of 95.7% and 97.8% at 8 h and 20 h, respectively, and a specificity of 94.4%, independent of the culture duration. Using a decision algorithm, this test was successful in identifying the carbapenemase class for 98.9% of tested CPE isolates (87/88 isolates). In total, the characterization was correct for 100%, 96.9%, and 100% of Ambler class A, B, and D isolates, respectively. Therefore, this test allows detection of carbapenemase activity in 8 h and characterization of carbapenemase classes, according to the Ambler classification, in 20 h. The CIMplus test represents a simple, affordable, easy-to-read, and accurate tool that can be used without any specific equipment.

Utility of CHROMagar mSuperCARBA for surveillance cultures of carbapenemase-producing Enterobacteriaceae.

Culture of carbapenemase-producing Enterobacteriaceae (CPE) as part of active surveillance is one of the most useful strategies for successful infection control programmes. Our objective was to compare the recently introduced CHROMagar mSuperCARBA agar for CPE detection in surveillance cultures from perineal swabs with the US Centers for Disease Control and Prevention method. Our results showed that this agar is a useful and affordable alternative (sensitivity 93.05%, specificity 96.21%, diagnostic accuracy 95.2%) to detect CPE in hospital settings.

Survey of screening methods, rates and policies for the detection of carbapenemase-producing Enterobacteriaceae in English hospitals

Multi-drug-resistant Gram-negative bacteria are of major clinical concern. The increasing prevalence of carbapenemase-producing Enterobacteriaceae (CPE), resistant to all beta-lactams including carbapenems and able to colonize the large intestine, represents a key threat. Rapid, accurate detection of intestinal CPE colonization is critical to minimize transmission, and hence reduce costly, difficult-to-treat CPE infections. There is currently no 'gold standard' CPE detection method. A survey of diagnostic laboratories in England found considerable heterogeneity in diagnostic CPE testing methods and procedures.

Utility of a novel chromogenic medium as a screening method in the detection of carbapenemase producing Enterobacteriaceae.

INTRODUCTION:With the emergence of multidrug resistant Gram-negative bugs, there is an urgent need for rapid detection of these resistant organisms.AIM:This study was performed to assess the utility of a novel chromogenic medium in the detection of carbapenemase producing Enterobacteriaceae from various clinical specimens.MATERIALS AND METHODS:A total of 202 isolates of Enterobacteriaceae, which were resistant to meropenem (10 μg) disc by standard disc diffusion method, were analyzed over a period of 6 months. These isolates were subjected to the modified Hodge test (MHT) and inoculated onto the chromogenic medium. Following which the results were analyzed.RESULTS:It was observed that 76.73% of the Enterobacteriaceae gave a positive result on the MHT, 18.31% were negative and 4.95% gave indeterminate result. While 88.11% produced growth on the chromogenic medium, 6.93% yielded no growth and 4.95% gave variable results. Concordance in the results of the two tests was found to be 65.34%.CONCLUSION:Enterobacteriaceae are emerging to be carbapenem resistant and are responsible for the soaring rates of Healthcare Associated Infections (HAIs), especially among critically ill patients. Hence, early detection of the same is important in controlling HAIs.

Evaluation of the RAPIDEC® CARBA NP and β-CARBA® tests for rapid detection of Carbapenemase-producing Enterobacteriaceae

The analytical performances of the RAPIDEC CARBA NP® (bioMérieux) and the β-CARBA® (Bio-Rad) tests were evaluated for the rapid detection of any known type of carbapenemases in Enterobacteriaceae. An international collection of 149 enterobacterial isolates comprising 111 Carbapenemase-Producing Enterobacteriaceae (CPE) and 38 non-carbapenemase producers was used. CPE included 32 carbapenemase producers of class A (18 KPC-2, 1 FRI-1, 5 SME and 8 IMI), 33 of class B (13 NDM, 11 VIM and 9 IMP) and 46 of class D (15 OXA-48, 14 OXA-181, 10 OXA-204, 3 OXA-232 and 4 OXA-162). The RAPIDEC CARBA NP® and the β-CARBA® tests were performed in strict accordance to the manufacturer's instructions and results were read within 2 h and 30 min, respectively. RAPIDEC CARBA NP® detected 104/111 CPE isolates compared to 72/111 for the β-CARBA® test. The overall sensitivity and specificity were 93.7% and 100%, respectively, for the RAPIDEC CARBA NP® test, and 64.9% and 90%, respectively, for the β-CARBA® test. The β-CARBA® test failed to detect all the non-KPC class A carbapenemases (14/14) and most (24/31) of the OXA-48-like producers (OXA-162, OXA-181, OXA-204 and OXA-232), and detected 1/1 OXA-163 and 1/1 OXA-405 as carbapenemase producers whereas these enzymes are rather defined as non carbapenemases. RAPIDEC CARBA NP® test exhibited better performances than those of the β-CARBA® test and confirmed to be a reliable tool for the detection of CPE, especially for OXA-48-like producers.

Multicenter evaluation of the RAPIDEC® CARBA NP test for rapid screening of carbapenemase-producing Enterobacteriaceae and Gram-negative nonfermenters from clinical specimens

The rapid diagnosis of carbapenemase-producing (CP) bacteria is essential for the management of therapy and infection control. In this study, RAPIDEC® CARBA NP (RCNP) was evaluated for the rapid screening of CP Enterobacteriaceae, Acinetobacter baumannii complex, and Pseudomonas aeruginosa from clinical specimens collected at five Italian hospitals. Firstly, each site tested 20 well-characterized strains in a blinded fashion. Secondly, each center prospectively tested 25 isolates from blood cultures processed with a rapid workflow (6h after subculture) and 25 isolates from other specimens processed after an overnight culture. The presence of carbapenemases was confirmed by multiplex real-timePCRs targeting carbapenemase genes. RCNP presented an overall sensitivity, specificity, positive predictive value, and negative predictive value of 70%, 94%, 82%, and 89%, respectively, with a higher performance in detection of CP Enterobacteriaceae and a poorer performance in detection of CP A. baumannii complex. With isolates from blood cultures, RCNP could significantly reduce the time required for identification of CP Enterobacteriaceae (less than 9h since the positivization of blood cultures).

Development of selective medium for IMP-type carbapenemase-producing Enterobacteriaceae in stool specimens

BackgroundIdentification of carbapenemase-producing Enterobacteriaceae (CPE) in faecal specimens is challenging. This fact is particularly critical because low-level carbapenem-resistant organisms such as IMP-producing CPE are most prevalent in Japan. We developed a modified selective medium more suitable for IMP-type CPE.MethodsFifteen reference CPE strains producing different types of β-lactamases were used to evaluate the commercially available CHROMagar KPC and chromID CARBA as well as the newly prepared MC-ECC medium (CHROMagar ECC supplemented with meropenem, cloxacillin, and ZnSO4) and M-ECC medium (CHROMagar ECC supplemented with meropenem and ZnSO4). A total of 1035 clinical samples were then examined to detect CPE using chromID CARBA and M-ECC medium.ResultsAll tested strains producing NDM-, KPC-, and OXA-48-carbapenemases were successfully cultured in the media employed. Although most of the IMP-positive strains did not grow in CHROMagar KPC, chromID CARBA, or MC-ECC, all tested strains grew on M-ECC. When faecal samples were applied to the media, M-ECC medium allowed the best growth of IMP-type CPE with a significantly higher sensitivity (99.3%) than that of chromID CARBA (13.9%).ConclusionsM-ECC medium was determined as the most favourable selective medium for the detection of IMP-type CPE as well as other types of CPE.

Molecular epidemiology of carbapenemase-producing Enterobacteriaceae in a primary care hospital in Japan, 2010-2013.

Recently, carbapenemase-producing Enterobacteriaceae (CPE) have been spreading worldwide and have become a threat in healthcare systems. We investigated the isolation frequency and molecular epidemiological characteristics of CPE isolated from clinical samples collected at a primary care hospital over the four years of 2010-2013 in Japan. CPE were detected in 17 (0.34%) of 4875 isolates by the broth microdilution method, sodium mercaptoacetate inhibition test, and modified Hodge test using meropenem disks. The frequency of CPE isolates was 0.09% in 2010, 0.17% in 2011, 0.16% in 2012 and 0.82% in 2013. Isolates positive for carbapenemase included Klebsiella pneumoniae (0.92%), Escherichia coli (0.12%), Enterobacter cloacae (0.80%), Klebsiella oxytoca (0.55%), Enterobacter aerogenes (0.81%) and Proteus mirabilis (0.08%). Antimicrobial susceptibility testing showed low MICs for piperacillin-tazobactam, amikacin, ciprofloxacin and levofloxacin, and only one multidrug-resistant strain. The carbapenemase genotype of all strains was IMP-6, and 94% of the strains were simultaneous CTX-M-2 producers. Two K.pneumoniae and 3 E.coli isolates showed the same pulsed-field gel electrophoresis group. Multilocus sequence typing detected no international high-risk clone types. Plasmid replicon typing detected IncN from all CPE strains, and IncF and IncFIB were simultaneously detected in 24% and 18%, respectively. All patients with detected CPE were inpatients, and many were elderly long-term hospitalized patients or had a history of prior vancomycin or levofloxacin antibiotic administration. The rapid spread of CPE is a concern in Japan. Preventive measures must be implemented against the spread of CPE after considering the epidemiological trend of CPE detection, antibiograms, and risk factors.

Antimicrobial susceptibility testing in predicting the presence of carbapenemase genes in Enterobacteriaceae in South Africa.

BackgroundCarbapenem-resistant Enterobacteriaceae (CRE) is a concern in South Africa and worldwide. It is therefore important that these organisms be accurately identified for infection prevention control purposes.MethodIn this study 1193 suspected CREs from 46 laboratories from seven provinces in South Africa were assessed to confirm the prevalence of carbapenemase genes from our referral diagnostic isolates for the period 2012 to 2015. We compared the antimicrobial susceptibility testing method used in the reference laboratory to the polymerase chain reaction (PCR) which is used as the gold standard. Organism identification and antimicrobial susceptibility testing were performed using automated systems and DNA was extracted using a crude boiling method. The presence of carbapenemase-producing genes (bla NDM, bla KPC, bla OXA-48&variants, bla GES, bla IMP and bla VIM) was screened for using a multiplex real-time PCR.ResultsSixty-eight percent (n = 812) of the isolates harboured a carbapenemase-producing gene; the three most common genes included: bla NDM, bla OXA-48&variants and bla VIM. Majority of the carbapenemase producing Enterobacteriaceae (CPE) isolates were Klebsiella species (71 %). The Microscan® Walkaway system used for the screening of carbapenemase production was 98 % sensitive with a minimal inhibitory concentration (MIC) breakpoint of less than 0.5 as susceptible for ertapenem and a low specificity (13 %).ConclusionFrom this study we can conclude that carbapenemase-producing Enterobacteriaceae is increasing in South Africa and the use of phenotypic methods for detection of CPEs showed good sensitivity but lacked specificity.

Modification and evaluation of the Carba NP test by use of paper strip for simple and rapid detection of carbapenemase-producing Enterobacteriaceae.

Carbapenemase-producing Enterobacteriaceae (CPE) isolates have now emerged worldwide. We therefore modified the phenotypic Carba NP test by use of a filter paper strip for easily and rapidly identifying CPE in routine laboratory. A collection of 56 CPE and carbapenemase-producing Pseudomonas spp. isolates (including 28 NDM-1, 11 IMP-14a, 1 IMP-1, 1 IMP-4, 1 IMP-9, 1 IMP-15, 4 VIM-2, 1 VIM-1, 1 IMP-14a with VIM-2, 3 OXA-48, 3 OXA-181 and 1 KPC-2 producers) and 41 non-CPE isolates (including 19 ESBL, 7 pAmpC, 3 AmpC, 9 ESBL with pAmpC and 3 non-ESBL & non-AmpC producers) as confirmed by the PCR methods were tested by the paper strip method using pharmaceutical imipenem/cilastatin as a substrate. Bacterial colonies of each isolate were applied directly on filter paper strips dropped with either imipenem-phenol red (test strip) or phenol red solution alone (control strip). The reaction was read within 5min. This test failed to detect 3 OXA-181, 2 OXA-48 and 3 IMP-14a producers (85.7% sensitivity), whereas no false positives were seen (100% specificity). Further evaluation of the paper strip test in 267 CPE screening-positive isolates from three hospitals by their medical technologists showed 92.0% sensitivity (100% for NDM producers) and 100% specificity compared with the PCR methods. Because of its ease, rapidness and cost effective, the paper strip test has a potential for routine CPE testing in low-resource laboratories particularly in areas with high prevalence of NDM enzymes, leading to appropriate antimicrobial therapy and infection control strategy.

Detection and epidemiology of carbapenemase producing Enterobacteriaceae in the Netherlands in 2013-2014.

Laboratory detection of carbapenemase-producing Enterobacteriaceae (CPE) is complicated. Screening with MIC values below clinical breakpoints followed by genotypic confirmation is recommended. We evaluated the application of recommended CPE screening and confirmation methods and provide an overview of CPE epidemiology in E. coli and K. pneumoniae in the Netherlands. Data on E. coli and K. pneumoniae isolates with elevated meropenem (>0.25mg/L) and/or imipenem (>1mg/L) MIC values in 2013-2014 were selected from the Infectious Disease Surveillance Information System for Antibiotic Resistance. Laboratories were requested to provide additional results of any confirmatory testing performed. Confirmation of elevated carbapenem MIC values using gradient testing was performed in 59.8% of eligible isolates. Confirmatory testing showed elevated MIC values in 8% of E. coli and 32% of K. pneumoniae isolates. The overall proportion of confirmed non-susceptible E. coli and K. pneumoniae was 0.01% and 0.16%, respectively. Genotypic confirmation was performed in 61.0% of isolates with confirmed elevated carbapenem MIC values. A carbapenemase gene was identified in 47% of E. coli and 65% of K. pneumoniae isolates. OXA-48, NDM and KPC were the most frequently found carbapenemase genes. The majority (62%) of CPE isolates was detected through targeted screening. CPE are a rare finding in the Netherlands. Adherence to the national guideline is suboptimal and differs between laboratories, implying a risk of inadequate CPE detection. Since accurate identification of CPE is the first step in prevention of CPE spread, successful implementation of guidelines for testing and reporting of CPE is essential.

Isolation demand from carbapenemase-producing Enterobacteriaceae screening strategies based on a West London hospital network

To estimate the isolation demands arising from high-risk specialty-based screening for carbapenemase-producing Enterobacteriaceae (CPE), and the potential fraction of CPE burden detected. Clinical specialty groups from three London hospitals were ranked by incidence of carbapenem resistance among Escherichia coli and Klebsiella spp. Contact precaution bed-days were estimated for three screening strategies: Strategy 1, 'circulation science and renal medicine'; Strategy 2, Strategy 1 plus 'specialist services'; and Strategy 3, Strategy 2 plus 'private patients'. Isolation bed occupancy rates and potential CPE detection rates were estimated. Of 99,105 admissions to the three hospitals in Financial Year 2014/15, Strategies 1, 2 and 3 would have screened 4371 (4.4%), 7482 (7.6%), and 13,542 (13.7%) patients, respectively. The specialties' isolation bed occupancy rates varied between 3% and 696% depending on strategy, number of consecutive tests, and whether or not pre-emptive isolation had been applied. Expected detection rates of the potential CPE burden in the hospital network would have varied between 17.1% and 47.5%. High-risk specialty-based screening has the potential to detect nearly half of the potential CPE burden, and would be more pragmatic than patient-level risk-factor-based screening. Pre-emptive isolation increases isolation requirements substantially. CPE screening strategies need to balance risk and resources.

Comparison of the in-house made Carba-NP and Blue-Carba tests: Considerations for better detection of carbapenemase-producing Enterobacteriaceae

The in-house Carba-NP and Blue-Carba tests were compared using 30 carbapenemase- and 33 non-producing Enterobacteriaceae. Tests were read by three operators. 100% sensitivity was reported for both tests, but Carba-NP was slightly more specific than Blue-Carba (98.9% vs. 91.7%). We describe potential sources of error during tests' preparation and reading.

Evaluation of Diagnostic Performance of RAPIDEC CARBA NP Test for Carbapenemase-ProducingEnterobacteriaceae

Background: Extended-spectrum β-lactamase (ESBL)producing Enterobacteriaceae are resistant to most β-lactam antibiotics except carbapenems. In recent years, infrequently isolated Enterobacteriaceae that produce carbapenemase pose a serious threat in the selection of appropriate therapeutic antibiotics. The rapid detection method of carbapenemase-producing Enterobacteriaceae (CPE) is necessary to prevent the spread of CPE into healthcare facilities. Methods: One hundred clinical Enterobacteriaceae isolates (Klebsiella pneumoniae 40, Escherichia coli 40, others 20) showing susceptibility to carbapenems and positivity in the CLSI ESBL phenotypic test from November 2015 to March 2016 and 59 stocked Enterobacteriaceae isolates harboring resistance genes producing carbapenemase (K. pneumoniae 56, Enterobacter cloacae 2, E. coli 1; types of CPE: KPC 36, GES 12, NDM 6, VIM 2, OXA 2, IMP 1) were subjected to the RAPIDEC CARBA NP test (bioMerieux, France) and CPE phenotypic test using the modified Hodge test (MHT) and carbapenemase inhibition test. Results: All of the 100 Enterobacteriaceae isolates with carbapenem susceptibility and ESBL positivity were negative on the RAPIDEC CARBA NP test and CPE phenotypic test. Of 59 stock CPE isolates, 53 and 42 showed positive results to the RAPIDEC CARBA NP test and MHT, respectively. The sensitivity and specificity of the RAPIDEC CARBA NP test for detecting CPE were 89.8% and 100%, respectively. Conclusion: The RAPIDEC CARBA NP test is simple and produces a result within 3 hr. In conclusion, the test is a useful screen for detecting CPE because it shows high sensitivity and specificity for CPE detection. (Ann Clin Microbiol 2016;19:59-64)

What Is the Appropriate Meropenem MIC for Screening of Carbapenemase-Producing Enterobacteriaceae in Low-Prevalence Settings?

Infection with carbapenemase-producing Enterobacteriaceae (CPE) has been shown to cause significant illness among hospitalized patients. Given the paucity of treatment options, there is a critical need to stop the spread of CPE. However, screening for the presence of CPE in laboratory settings has been challenging. In order to assess the effectiveness of current CPE detection guidelines, we analyzed the meropenem MIC distribution for a large set of clinical Enterobacteriaceae isolates. A total of 1,022 isolates submitted to the Public Health Ontario Laboratories (PHOL) from January 2011 to March 2014 were examined. Only isolates displaying a meropenem or ertapenem MIC of ≥ 0.25 or ≥ 1 μg/ml, respectively, were included. Carbapenemase-positive isolates were identified by multiplex PCR. We identified 189 isolates positive for carbapenemases, which primarily comprised NDM, KPC, and OXA-48-like carbapenemases, and these isolates were largely Klebsiella spp., Escherichia coli, and Enterobacter spp. Interestingly, 14 to 20% of these isolates displayed meropenem MICs within the susceptible range on the basis of CLSI and EUCAST breakpoint interpretive criteria. While the majority of meropenem-susceptible CPE isolates were observed to be E. coli, meropenem susceptibility was not exclusive to any one species/genus or carbapenemase type. Application of CLSI screening recommendations captured only 86% of carbapenemase-producing isolates, whereas application of EUCAST recommendations detected 98.4% of CPE isolates. In a region with a low carbapenemase prevalence, meropenem-based screening approaches require a cutoff MIC near the epidemiological wild-type threshold in order to achieve nearly optimal CPE identification.

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

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.